Itescu Y, Schwarz R, Donihue CM, Slavenko A, Roussos SA, Sagonas K, Valakos ED, Foufopoulos J, Pafilis P, Meiri S. Inconsistent patterns of body size evolution in co‐occurring island reptiles. Global Ecology and Biogeography. Submitted.
Bertsatos A, Papageorgopoulou C, Valakos E, Chovalopoulou M-E. Investigating the sex-related geometric variation of the human cranium. International Journal of Legal Medicine [Internet]. 2018. WebsiteAbstract
Accurate sexing methods are of great importance in forensic anthropology since sex assessment is among the principal tasks when examining human skeletal remains. The present study explores a novel approach in assessing the most accurate metric traits of the human cranium for sex estimation based on 80 ectocranial landmarks from 176 modern individuals of known age and sex from the Athens Collection. The purpose of the study is to identify those distance and angle measurements that can be most effectively used in sex assessment. Three-dimensional landmark coordinates were digitized with a Microscribe 3DX and analyzed in GNU Octave. An iterative linear discriminant analysis of all possible combinations of landmarks was performed for each unique set of the 3160 distances and 246,480 angles. Cross-validated correct classification as well as multivariate DFA on top performing variables reported 13 craniometric distances with over 85% classification accuracy, 7 angles over 78%, as well as certain multivariate combinations yielding over 95%. Linear regression of these variables with the centroid size was used to assess their relation to the size of the cranium. In contrast to the use of generalized procrustes analysis (GPA) and principal component analysis (PCA), which constitute the common analytical work flow for such data, our method, although computational intensive, produced easily applicable discriminant functions of high accuracy, while at the same time explored the maximum of cranial variability.
Xanthopoulou P, Valakos E, Youlatos D, Nikita E. Assessing the accuracy of cranial and pelvic ageing methods on human skeletal remains from a modern Greek assemblage. [Internet]. 2018. WebsiteAbstract
The present study tests the accuracy of commonly adopted ageing methods based on the morphology of the pubic symphysis, auricular surface and cranial sutures. These methods are examined both in their traditional form as well as in the context of transition analysis using the ADBOU software in a modern Greek documented collection consisting of 140 individuals who lived mainly in the second half of the twentieth century and come from cemeteries in the area of Athens. The auricular surface overall produced the most accurate age estimates in our material, with different methods based on this anatomical area showing varying degrees of success for different age groups. The pubic symphysis produced accurate results primarily for young adults and the same applied to cranial sutures but the latter appeared completely inappropriate for older individuals. The use of transition analysis through the ADBOU software provided less accurate results than the corresponding traditional ageing methods in our sample. Our results are in agreement with those obtained from validation studies based on material from across the world, but certain differences identified with other studies on Greek material highlight the importance of taking into account intra- and inter-population variability in age estimation.
Sagonas K, Valakos ED, Lymberakis P, Pafilis P. Traits of reproduction and feeding of the European Green Lizard, Lacerta viridis (LAURENTI, 1768), at the southern edge of its distribution. HERPETOZOA. 2018;30(3-4):115-129.
Pafilis P, Maragou P, Sagonas K, Valakos E. Partitioning thermal habitat on a vertical rock, a herculean task. Journal of Thermal Biology [Internet]. 2017;70:54 - 60. WebsiteAbstract
Abstract Species occurring in sympatry have to effectively segregate their niche in order to co-exist. In the case of ectotherms in particular, the very important parameter of thermal biology has to be taken into account. Here we investigated the thermoregulatory effectiveness (E) of two endemic Greek lizards (Hellenolacerta graeca and Podarcis peloponnesiacus) that live syntopically on a rocky cliff in the Peloponnese. We presumed that the two species would select different microhabitats, to avoid interspecific competition, and follow a similar thermoregulation pattern as they experience the same conditions. We also expected that E values for both species would differ depending on the season. Overall, we found that the two species had similar E values for each season but differentiated partial thermoregulatory attributes. Though they both occurred in the same types of microhabitat, H. graeca selected higher sites (average 99cm above ground) than P. peloponnesiacus (average 44cm). Also, the latter achieved higher preferred temperatures during summer and winter. Finally, the effectiveness of thermoregulation for both species varied interseasonally and received its highest values during summer, in response to the lowest thermal quality that was observed then. Similar studies stress the importance of thermal shifts for ectotherm co-existence.
Oikonomopoulou E-K, Valakos E, Nikita E. Population-specificity of sexual dimorphism in cranial and pelvic traits: evaluation of existing and proposal of new functions for sex assessment in a Greek assemblage. International Journal of Legal Medicine. 2017:1-8.
Pafilis P, Sagonas K, Kapsalas G, Foufopoulos J, Valakos ED. Sex does not affect tail autotomy in lacertid lizards. Acta Herpetologica. 2017;12(1):19-27.
Foufopoulos J, Roca V, White KA, Pafilis P, Valakos ED. Effects of island characteristics on parasitism in a Mediterranean lizard (Podarcis erhardii): A role of population size and island history?. North-Western Journal of Zoology [Internet]. 2017;13(1):70 - 76. Website
Karameta E, Mizan VL, Sagonas K, Sfenthourakis S, Valakos ED, Pafilis P. Ontogenetic shifts in the digestive efficiency of an insectivorous lizard (Squamata: Agamidae). Salamandra [Internet]. 2017;53(2):321 - 326. Website
Sagonas K, Karambotsi N, Bletsa A, Reppa A, Pafilis P, Valakos ED. Tail regeneration affects the digestive performance of a Mediterranean lizard. Naturwissenschaften. 2017;104(3-4):22.Abstract
In caudal autotomy, lizards shed their tail to escape from an attacking predator. Since the tail serves multiple functions, caudal regeneration is of pivotal importance. However, it is a demanding procedure that requires substantial energy and nutrients. Therefore, lizards have to increase energy income to fuel the extraordinary requirements of the regenerating tail. We presumed that autotomized lizards would adjust their digestion to acquire this additional energy. To clarify the effects of tail regeneration on digestion, we compared the digestive performance before autotomy, during regeneration, and after its completion. Tail regeneration indeed increased gut passage time but did not affect digestive performance in a uniform pattern: though protein income was maximized, lipid and sugar acquisition remained stable. This divergence in proteins may be attributed to their particular role in tail reconstruction, as they are the main building blocks for tissue formation.
Sagonas K, Kapsalas G, Valakos E, Pafilis P. Living in sympatry: The effect of habitat partitioning on the thermoregulation of three Mediterranean lizards. J Therm Biol. 2017;65:130-137.Abstract
The ability for effective, accurate and precise thermoregulation is of paramount importance for ectotherms. Sympatric lizards often partition their niche and select different microhabitats. These microhabitats, however, usually differ in their thermal conditions and lizards have to adapt their thermoregulation behavior accordingly. Here, we evaluated the impact of habitat partitioning on the thermal biology of three syntopic, congeneric lacertids (Podarcis peloponnesiacus, P. tauricus and P. muralis) from central Peloponnese, Greece. We assessed thermoregulation effectiveness (E) using the three standard thermal parameters: body (Tb), operative (Te) and preferred (Tpref) temperatures. We hypothesized that the microhabitats used by each species would differ in thermal quality. We also predicted that all species would effectively thermoregulate, as they inhabit a thermally challenging mountain habitat. As expected, the partition of the habitat had an effect on the thermoregulation of lizards since microhabitats had different thermal qualities. All three species were effective and accurate thermoregulators but one of them achieved smaller E values as a result of the lower Tb in the field. This discrepancy could be attributed to the cooler (but more benign) thermal microhabitats that this species occupies.
Lymberakis P, Valakos ED, Sagonas K, Pafilis P. The castaway: characteristic islet features affect the ecology of the most isolated European lizard. Acta Herpetologica. 2016;11(2):161-169.
Pafilis P, Lymberakis P, Sagonas K, Valakos E. The particularities of a remote islet shape the thermoregulatory profile of an endemic Mediterranean lizard. Journal of Thermal Biology. 2016;61:55-60.
Kotsakiozi P, Parmakelis A, Konstantakis A, Valakos ED. Climatic conditions driving a part of changes in the biochemical composition in land snails: Insights from the endangered Codringtonia (Gastropoda: Pulmonata). Biologia. 2016;71(8):903-916.
Pafilis P, Meiri S, Sagonas K, Karakasi D, Kourelou E, Valakos ED. Body size affects digestive performance in a Mediterranean lizard. The Herpetological Journal. 2016;26(3):199-205.
Belasen A, Brock K, Li B, Chremou D, Valakos E, Pafilis P, Sinervo B, Foufopoulos J. Fine with heat, problems with water: Microclimate alters water loss in a thermally adapted insular lizard. Oikos [Internet]. 2016. Website
Sagonas K, Rota IA, Tsitsilonis OE, Pafilis P, Valakos ED. Infection risk dictates immunological divergence among populations in a Mediterranean lizard. J Evol Biol. 2016;29(9):1680-8.Abstract
The ability of vertebrates to evolve different defence strategies in response to varying parasitism regimes remains poorly understood. Hosts may adopt two different strategies to defend themselves against parasites: tolerance (hosts alleviate the negative fitness consequences of parasite infection) and resistance (hosts strengthen their immune response as parasite burden increases). Both strategies are effective, but fitness has been reported to decline faster in less-tolerant individuals. Here, we assessed the number of splenocytes and the cell-mediated response (proxies for resistance) and body condition (a proxy for tolerance) in four populations of a Greek endemic lizard (Podarcis gaigeae), each exposed to different infection risks (defined as the cumulative effect of parasite burden and duration of exposure). We anticipated that populations with heavy parasite burden would enhance the efficacy of their immune response (resistance) compared to lizards deriving from parasite-poor habitats. We also predicted that populations with longer exposure to parasites would be adopted and be more tolerant. Each factor (duration of exposure and parasite burden) had a distinct effect on the immune response, and thus, our results were rather complicated. Lizards with heavy parasite burden and aperiodic exposure demonstrated resistance, whereas lizards with heavy parasite burden and chronic exposure were more tolerant. Populations with low parasite burden and minimal exposure were more resistant. Our results suggest that the development of some immunological strategies may be differentiated under different infection risks, even within the same species.
Chovalopoulou M-E, Valakos ED, Manolis SK. Sex determination by three-dimensional geometric morphometrics of the vault and midsagittal curve of the neurocranium in a modern Greek population sample. Homo. 2016;67(3):173-87.Abstract
The aim of this study is to assess sexual dimorphism of adult crania in the vault and midsagittal curve of the vault using three-dimensional geometric morphometric methods. The study sample consisted of 176 crania of known sex (94 males, 82 females) belonging to individuals who lived during the 20th century in Greece. The three-dimensional co-ordinates of 31 ecto-cranial landmarks and 30 semi-landmarks were digitized using a MicroScribe 3DX contact digitizer. Generalized Procrustes analysis (GPA) was used to obtain size and shape variables for statistical analysis. Shape, size and form analyses were carried out by logistic regression and three discriminant function analyses. Results indicate that there are shape differences between sexes. Females in the region of the parietal bones are narrower and the axis forming the frontal and occipital bones is more elongated; the frontal bone is more vertical. Sex-specific shape differences give better classification results in the vault (79%) compared with the midsagittal curve of the neurocranium (68.8%). Size alone yielded better results for cranial vault (82%), while for the midsagittal curve of the vault the result is poorer (68.1%). As anticipated, the classification accuracy improves when both size and shape are combined (89.2% for vault, and 79.4% for midsagittal curve of the vault). These latter findings imply that, in contrast to the midsagittal curve of the neurocranium, the shape of the cranial vault can be used as an indicator of sex in the modern Greek population.
Mina D, Sagonas K, Fragopoulou AF, Pafilis P, Skouroliakou A, Margaritis LH, Tsitsilonis OE, Valakos ED. Immune responses of a wall lizard to whole-body exposure to radiofrequency electromagnetic radiation. Int J Radiat Biol. 2016;92(3):162-8.Abstract
PURPOSE: During the last three decades, the number of devices that emit non-ionizing electromagnetic radiation (EMR) at the wireless communication spectrum has rapidly increased and possible effects on living organisms have become a major concern. The purpose of this study was to investigate the effects of radiofrequency EMR emitted by a widely used wireless communication device, namely the Digital Enhanced Communication Telephony (DECT) base, on the immune responses of the Aegean wall lizard (Podarcis erhardii). MATERIALS AND METHODS: Adult male lizards were exposed 24 h/day for 8 weeks to 1880-1900 MHz DECT base radiation at average electric field intensity of 3.2 V/m. Immune reactivity was assessed using the phytohemagglutinin (PHA) skin swelling and mixed lymphocyte reaction (MLR) tests. RESULTS: Our results revealed a noticeable suppression (approximately 45%) of inflammatory responses in EMR-exposed lizards compared to sham-exposed animals. T cell-mediated responses were marginally affected. CONCLUSION: Daily radiofrequency EMR exposure seems to affect, at least partially, the immunocompetence of the Aegean wall lizard.
Chovalopoulou M-E, Valakos ED, Manolis SK. Sex determination by three-dimensional geometric morphometrics of craniofacial form. Anthropol Anz. 2016;73(3):195-206.Abstract
SUMMARY: The purpose of the present study is to define which regions of the cranium, the upper-face, the orbits and the nasal are the most sexually dimorphic, by using three-dimensional geometric morphometric methods, and investigate the effectiveness of this method in determining sex from the shape of these regions. The study sample consisted of 176 crania of known sex (94 males, 82 females) belonging to individuals who lived in Greece during the 20(th) century. The three-dimensional co-ordinates of 31 ecto-cranial landmarks were digitized using a MicroScribe 3DX contact digitizer. Goodall's F-test was performed in order to compare statistical differences in shape between males and females. Generalized Procrustes Analysis (GPA) was used to obtain size and shape variables for statistical analysis. Shape, Size and Form analyses were carried out by logistic regression and discriminant function analysis. The results indicate that there are shape differences between the sexes in the upper-face and the orbits. The highest shape classification rate was obtained from the upper-face region. The centroid size of the caraniofacial and the orbital regions was smaller in females than males. Moreover, it was found that size is significant for sexual dimorphism in the upper-face region. As anticipated, the classification accuracy improves when both size and shape are combined. The findings presented here constitute a firm basis upon which further research can be conducted.
SAGONAS Κ, Pafilis P, Lymberakis P, Valakos ED. Trends and patterns in the feeding ecology of the widespread Balkan green lizard Lacerta trilineata (Squamata: Lacertidae) in insular and continental Greece. North-Western Journal of Zoology. 2015;11(1):117-126.
Dimaki M, Chondropoulos B, Legakis A, Valakos E, Vergetopoulos M. New data on the distribution and population density of the African Chameleon, Chamaeleo africanus and the Common Chameleon, Chamaeleo chamaeleon in Greece. Hyla. 2015;1:36-43.
Sagonas K, Pafilis P, Valakos ED. Effects of insularity on digestion: living on islands induces shifts in physiological and morphological traits in island reptiles. Naturwissenschaften. 2015;102(9-10):55.Abstract
Living on islands entails numerous challenges for animals, among which resource scarcity stands out. In order to survive, animals have to optimize energy acquisition. We examined the impact of insularity on digestion comparing a series of physiological and morphological traits of adult males between insular and mainland populations of the Balkan green lizard. Island lizards had longer gastrointestinal tracts and gut passage times and higher digestive efficiencies. The dissection of the hindgut revealed an unexpected finding, the presence of cecal valves that were more frequent in island lizards. Thanks to all above islanders retain food for longer periods and thus maximize energy income and increase the amount of the extracted nutrients. That way, they secure energy income from the limited, in time and quantity, food resources of the islands.
Michopoulou E, Nikita E, Valakos ED. Evaluating the efficiency of different recording protocols for entheseal changes in regards to expressing activity patterns using archival data and cross-sectional geometric properties. Am J Phys Anthropol. 2015;158(4):557-68.Abstract
OBJECTIVES: In the past decade there have been extensive discussions on the potential utility of entheseal changes (EC) as activity markers. Nevertheless, no study to date has compared different EC recording protocols with respect to their correlation to activity patterns. MATERIALS AND METHODS: This article records changes on fibrocartilaginous entheses of the upper limbs of 90 male skeletons from the documented Athens Collection using the Hawkey and Merbs (Int J Osteoarchaeol 5 (1995) 324-338), Mariotti et al. (Collegium Antropol 28 (2004) 145-159), and Villotte et al. (Am J Phys Anthropol 142 (2010) 224-234) recording schemes in order to determine which one exhibits the highest correlation with activity. Activity is assessed by means of the recorded profession of each individual, as well as employing cross-sectional geometric properties. Generalized Linear Models are used to explore the impact of age, body mass, and activity on EC expression. RESULTS: Our results agree with previous studies that age is the primary factor determining EC, whereas body mass is the second most influential factor. In contrast, activity in the form of profession or cross-sectional geometry rarely showed a significant correlation to EC expression and no clear pattern could be discerned irrespective of the recording technique. However, bilateral differences in the impact of age and body mass in EC expression were traced and may relate to activity patterns. CONCLUSIONS: The differences found in the bilateral impact of age and body mass highlight the fact that the activity patterns of the individuals under examination must play an underlying role to EC expression, though current recording schemes for EC do not capture this, rendering further work in the direction of developing more elaborate recording standards imperative.
Anastopoulou I, Eliopoulos C, Valakos ED, Manolis SK. Application of Purkait's triangle method on a skeletal population from southern Europe. Forensic Sci Int. 2014;245:203.e1-4.Abstract
The existence of sexual dimorphism in individual elements of the human skeleton allows sex determination and significantly enhances the identification of fragmentary skeletal material. Traditionally, the pelvis and the skull are used for an accurate sex determination. Sometimes they are not available and alternative methods have to be used. The aim of this work is to study the sexual dimorphism of the proximal portion of the posterior femur by analyzing the biometric data of the Purkait's triangle. The studied sample comprises 203 individuals (112 males and 91 females) from the Modern Human Skeletal Reference Collection (The Athens Collection) of the Department of Animal & Human Physiology (National & Kapodistrian University of Athens). The biometric data were analyzed by Discriminant Analysis and equations were generated for sex determination, which gave an overall correct classification of 78.3%. For the right and the left femur the percentages of correct classification were 77.8% and 75.9% respectively. These accuracy rates were compared to those of an Indian population and were found to be lower (86.5% for males and 86.3% for females). The study of sexual dimorphism (SD) in Greek, Indian, European-American and African-American populations gave interesting results. The AB diameter in the Greek sample shows the lowest degree of SD while the AC diameter shows the highest. In the other three population samples, the BC diameter shows the highest degree of SD. We assume that the femur anatomy of the Greeks is the major cause that the Purkait method does not give high rates of correct classification. It is therefore advisable that practitioners exercise caution when using this method on skeletal material from Greece, especially in forensic contexts.
Sagonas K, Pafilis P, Lymberakis P, Donihue CM, Herrel A, Valakos ED. Insularity affects head morphology, bite force and diet in a Mediterranean lizard. Biological Journal of the Linnean Society. 2014;112:469-484.Abstract
Island environments differ with regard to numerous features from the mainland and may induce large-scale changes in most aspects of the biology of an organism. In this study, we explore the effect of insularity on the morphology and performance of the feeding apparatus, a system crucial for the survival of organisms. To this end, we examined the head morphology and feeding ecology of island and mainland populations of the Balkan green lizard, Lacerta trilineata. We predicted that head morphology, performance and diet composition would differ between sexes and habitats as a result of varying sexual and natural selection pressures. We employed geometric morphometrics to test for differences in head morphology, measured bite forces and analysed the diet of 154 adult lizards. Morphological analyses revealed significant differences between sexes and also between mainland and island populations. Relative to females, males had larger heads, a stronger bite and consumed harder prey than females. Moreover, island lizards differed in head shape, but not in head size, and, in the case of males, demonstrated a higher bite force. Islanders had a wider food niche breadth and included more plant material in their diet. Our findings suggest that insularity influences feeding ecology and, through selection on bite force, head morphology. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, ●●, ●●–●●.
Sagonas K, Poulakakis N, Lymberakis P, Parmakelis A, Pafilis P, Valakos ED. Molecular systematics and historical biogeography of the green lizards (Lacerta) in Greece: Insights from mitochondrial and nuclear DNA. Molecular Phylogenetics and Evolution. 2014;76:144-154.
Kotsakiozi P, Parmakelis A, Aggeli I-K, Gaitanaki C, Giokas S, Valakos ED. Water balance and expression of heat-shock protein 70 in Codringtonia species: A study within a phylogenetic framework. Journal of Molluscan Studies. 2014;doi: 10.1093/mollus/eyu042.Abstract
Seasonal differences in the water content of fourCodringtoniaspecies were investigated using specimens collected from the field. In addition, rate of water loss and expression of heat-shock protein 70 (Hsp70) were measured in a laboratory setting with sixCodringtoniaspecies subjected to a short-term heat shock. Using a phylogenetic framework, both the Hsp70 expression levels and the rate of water loss were inves tigated for their correlation with spatial and climatic variables. As indicated by the field-collected samples, during summer aestivation only C. helenaeexhibited a tendency for water loss. During the short-term heat shock the rate of water loss inC. helenaewas also significantly greater. No interspecific differences could be detected in the levels of Hsp70 in the species subjected to short-term heat shock. A singleCodringtoniaspecies seemed to maintain increased Hsp70 protein levels. In the species subjected to short-term heat shock, a positive relationship was found between Hsp70 levels and rate of water loss. On the other hand, the Hsp70 levels under normal conditions showed a negative correlation with altitude and mean summer precipitation of the sampling localities. Thus, species seem to adapt to harsher environmental conditions by maintaining higher levels of Hsp70.
CHOVALOPOULOU E.M., E.VALAKOS SKMANOLIS. Sex determination by three-dimensional geometric morphometrics of the palate and cranial base. Anthrop.Anz. J.Biol. Clinic. Anthrop. Anthrop.Anz. J.Biol. Clinic. Anthrop. 2013;70:407-425.
Kotsakiozi P, Rigal F, Valakos ED, Parmakelis A. Disentangling the effects of intraspecies variability, phylogeny, space, and climate on the evolution of shell morphology in endemic Greek land snails of the genus Codringtonia. Biological Journal of the Linnean Society. 2013;110:796-813.Abstract
Extensive variation in land snail shell morphology has been widely documented, although few studies have attempted to investigate the ecological and evolutionary drivers of this variation. Within a comparative phylogenetic framework, we investigated the temporal and spatial evolution of the shell morphology of the Greek endemic land snail genus Codringtonia. The contribution of both inter- and intraspecies shell differentiation in the overall shell variability is assessed. The effect of climate, space, and evolutionary history on the shell variability was inferred using a variance partitioning framework. For Codringtonia species, intraspecies divergence of shell traits contributes substantially to the overall shell variability. By decomposing this variability, it was shown that the overall shell size of Codringtonia clades is phylogenetically constrained, related to early speciation events, and strongly affected by large-scale spatial variability (latitudinal gradient). The effect of climate on shell size cannot be disentangled from phylogeny and space. Shell and, to a larger extent, aperture shape are not phylogenetically constrained, and appear to be mostly related to conspecific populations divergence events. Shell shape is substantially explained by both climate and space that greatly overlap. Aperture shape is mainly interpreted by medium to small-scale spatial variables. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, ●●, ●●–●●.
Sagonas K, Meiri S, Valakos ED, Pafilis P. The effect of body size on the thermoregulation of lizards on hot, dry Mediterranean islands. Journal of Thermal Biology. 2013;38:92-97.Abstract
Body size shapes the overall biology of organisms. We assessed the impact of size on temperature regulation in populations of normal-sized and large-bodied insular Mediterranean lizards (Podarcis gaigeae, Lacertidae). We hypothesized that large lizards would achieve higher body temperatures and thermoregulate more effectively than their smaller kin. Large- and small-bodied lizards share the same thermoregulation pattern, achieving similar body temperatures in the field. Large lizards, however, prefer higher set-point temperatures. Lizards in both populations thermoregulate effectively, but large lizards thermoregulated less effectively than normal sized lizards. The particular conditions at the islet that harbors the large-bodied population (harsh intraspecific competition) seem to account for this pattern.
Pafilis P, Anastasiou I, Sagonas K, Valakos ED. Grazing by goats on islands affects the populations of an endemic Mediterranean lizard. Journal of Zoology. 2013;290:255-264.Abstract
Grazing of goats on Mediterranean islets is a common practice. Its consequences on plant communities are well documented, although not on vertebrates. We aim to shed light on the effect of livestock farming on lizards by investigating five populations of the insular lizard, Podarcis gaigeae, differing in the duration and intensity of grazing. Data on grazing regime, invertebrate abundance, tick prevalence, infestation levels, gull nests and lizard densities were collected during a period of 6 consecutive years. Grazing had a negative impact on insect populations, thus decreasing food availability for lizards. Tick prevalence and infestation levels were higher in places of continuous grazing. Goat activity disturbed gulls, which avoid nesting, so depriving the islets of marine subsidies. As a consequence of all these factors, lizard densities were higher in ungrazed and lower in grazed biotopes. Grazing effects were more severe on islets communities than on the main island populations. Our data imply that management action should be taken to conserve the highly diverse islet populations.
Sagonas K, Valakos ED, Pafilis P. The impact of insularity on the thermoregulation of a Mediterranean lizard. Journal of Thermal Biology. 2013;38:480-486.Abstract
Abstract The overall biology of ectotherms is strongly affected by the thermal quality of the environment. The particular conditions prevailing on islands have a strong effect on numerous features of animal life. In this study we compared mainland and island populations of the lizard Lacerta trilineata and hypothesized that insularity would affect the thermoregulatory strategy. Continental habitats were of lower thermal quality, experiencing more intense fluctuations and had higher values of operative temperatures. Nevertheless mainland lizards selected for higher body temperatures in the lab and showed more effective thermoregulation during summer than their island peers. Lizards achieved similar body temperatures in the field in both types of habitat, underlining the importance of predation as a potential factor to mainland lizards that failed to reach their higher thermal preferences. Both island and mainland populations of L. trilineata have been adapted to their thermal environment, supporting the labile view on the evolution of thermal physiology for this species.
KELEPERTZIS E., A.ARGYRAKI EVALAKOSDAFTSISE. Distribution and accumulation of metals in tadpoles inhabiting the metalliferous streams of eastern chalkidiki, northeast Greece. Arch Envirom Contam. Toxicol.Arch Envirom Contam. Toxicol. 2012;63:409-420 .
Kotsakiozi P, Pafilis P, Giokas S, Valakos E. A comparison of the physiological responses of two land snail species with different distributional ranges. Journal of Molluscan StudiesJournal of Molluscan Studies. 2012;78:217-224.Abstract
Land snails usually exhibit cycles of activity and dormancy (aestivation or hibernation). The transition between these two states is accompanied by a range of behavioural and physiological responses to ensure their survival under adverse environmental conditions. Furthermore, aestivation plays an important role in shaping species' distribution patterns. We examined the seasonal patterns in biochemical tissue composition in relation to aspects of behavioural ecology in three land snail populations: one mainland and one insular population of the widespread Helix aspersa and a population (sympatric with the latter) of Helix figulina, a congeneric species with a narrow and declining distribution. Helix figulina aestivates in underground borrows, while H. aspersa spends the summer under stones and may interrupt aestivation when conditions become favourable. Prior to aestivation H. figulina accumulates metabolic fuels, which it consumes later during summer, and at the same time loses substantial body water and increases lactate dehydrogenase (LDH) activity. The insular H. aspersa population follows a similar pattern (regarding metabolites and LDH activity), with the difference that water loss is limited. However, the mainland population of H. aspersa deviates from this model with energy metabolites and water levels showing little variation throughout the year, while LDH activity is reduced. These differences probably reflect the particular behavioural and physiological patterns adopted by each species. The specialist and range-restricted H. figulina shows a constant and more predictable seasonal pattern, which may be effective for surviving in its historical biogeographic range, but it seems to be more vulnerable to possibly changing environmental conditions. On the other hand the generalist and cosmopolitan H. aspersa adopts a more flexible pattern that compensates for the effects of adverse conditions during aestivation and permits a more effective exploitation of energy resources.
Kotsakiozi P, Parmakelis A, Giokas S, Papanikolaou I, Valakos ED. Mitochondrial phylogeny and biogeographic history of the Greek endemic land-snail genus Codringtonia Kobelt 1898 (Gastropoda, Pulmonata, Helicidae). Molecular Phylogenetics and Evolution. 2012;62:681-692.Abstract
The aim of this work was to infer the phylogeny of the Greek endemic land-snail genus Codringtonia Kobelt 1898, estimate the time frame of the radiation of the genus, and propose a biogeographic scenario that could explain the contemporary distribution of Codringtonia lineages. The study took place in the districts of Peloponnese, Central Greece and Epirus of mainland Greece. Sequence data originating from three mtDNA genes (COI, COII, and 16S rDNA) were used to infer the phylogeny of the eight nominal Codringtonia species. Furthermore, the radiation time-frame of extant Codringtonia species was estimated using a relaxed molecular clock analysis and mtDNA substitution rates of land snails. The phylogenetic analysis supported the existence of six Codringtonia lineages in Greece and indicated that one nominal species (Codringtonia neocrassa) might belong to a separate genus distantly related to Codringtonia. The time frame of differentiation of Codringtonia species was placed in the Late Miocene-Pleistocene epoch. The dispersal-vicariance analysis performed indicated that most probably Codringtonia exhibited a north-to-south spread with the ancestral area being that of central Greek mainland, accompanied with duplication (speciation) and vicariance events. © 2011 Elsevier Inc.
Pafilis P, Foufopoulos J, Sagonas K, Runemark A, Svensson E, Valakos ED. Reproductive biology of insular reptiles: Marine subsidies modulate expression of the “Island Syndrome”. Copeia. 2011;2011:545-552.Abstract
Differences in ecological conditions can result in the evolution of dramatic inter-population shifts in whole suites of traits. We studied variation in reproductive output in three lizard populations of the Skyros Wall Lizard (Podarcis gaigeae, Lacertidae) endemic to the Skyros Archipelago (Greece), which live under similar climatic conditions but differ in predation pressure and food availability. Based on the ‘‘island syndrome’’ hypothesis, we predicted that females from island populations would produce larger, but fewer offspring. The study populations differ conspicuously in average body size, with males from the satellite Lakonissi and Diavates islets being respectively 20% and 39% larger than males from the main Skyros Island. Lizards from these predator-free islets produced eggs of larger size than the main Skyros population; however, they also produced significantly larger clutches than the Skyros population (2.31±0.83 and 2.73±1.0 vs. 1.97±0.58 eggs). All inter-population differences in clutch size, clutch volume, and egg size were explained by corresponding differences in average body size of the dams, revealing that across all populations, reproductive effort scaled similarly with maternal body size. There was no evidence of trade-offs between egg size and clutch size as generally encountered in many reptile taxa. The occurrence of this unusual pattern of reproductive investment among islet populations of giants is probably best explained by the occurrence of two underlying drivers: first, the substantial marine subsidies by resident seabird colonies and second, the existence of intense cannibalistic behaviors in the form of attacks to the tail and severe intraspecific predation on juveniles. This suggests that subsidies-driven gigantism in island endemics may free species from such trade-offs and allow a population to maximize reproductive output in multiple, normally conflicting dimensions.
Vervust B, Pafilis P, Valakos ED, Van Damme R. Anatomical and physiological changes associated with a recent dietary shift in the lizard Podarcis sicula. Physiological and Biochemical ZoologyPhysiological and Biochemical Zoology. 2010;83:632-642.Abstract
Dietary shifts have played a major role in the evolution of many vertebrates. The idea that the evolution of herbivory is physiologically constrained in squamates is challenged by a number of observations that suggest that at least some lizards can overcome the putative physiological difficulties of herbivory on evolutionary and even ecological timescales. We compared a number of morphological and physiological traits purportedly associated with plant consumption between two island populations of the lacertid lizard Podarcis sicula. Previous studies revealed considerable differences in the amount of plant material consumed between those populations. We continued the investigation of this study system and explored the degree of divergence in morphology (dentition, gut morphology), digestive performance (gut passage time, digestive efficiency), and ecology (endosymbiont density). In addition, we also performed a preliminary analysis of the plasticity of some of these modifications. Our results confirm and expand earlier findings concerning divergence in the morphology of feeding structures between two island populations of P. sicula lizards. In addition to the differences in skull dimensions and the prevalence of cecal valves previously reported, these two recently diverged populations also differ in aspects of their dentition (teeth width) and the lengths of the stomach and small intestine. The plasticity experiment suggests that at least some of the changes associated with a dietary shift toward a higher proportion of plant material may be plastic. Our results also show that these morphological changes effectively translate into differences in digestive performance: the population with the longer digestive tract exhibits longer gut passage time and improved digestive efficiency. © 2010 by The University of Chicago.
Runemark A, Hansson B, Pafilis P, Valakos E, Svensson E. Island biology and morphological divergence of the Skyros wall lizard Podarcis gaigeae: a combined role for local selection and genetic drift on color morph frequency divergence?. BMC Evolutionary BiologyBMC Evolutionary Biology. 2010;10:269.Abstract
BACKGROUND:Patterns of spatial variation in discrete phenotypic traits can be used to draw inferences about the adaptive significance of traits and evolutionary processes, especially when compared to patterns of neutral genetic variation. Population divergence in adaptive traits such as color morphs can be influenced by both local ecology and stochastic factors such as genetic drift or founder events. Here, we use quantitative color measurements of males and females of Skyros wall lizard, Podarcis gaigeae, to demonstrate that this species is polymorphic with respect to throat color, and the morphs form discrete phenotypic clusters with limited overlap between categories. We use divergence in throat color morph frequencies and compare that to neutral genetic variation to infer the evolutionary processes acting on islet- and mainland populations.RESULTS:Geographically close islet- and mainland populations of the Skyros wall lizard exhibit strong divergence in throat color morph frequencies. Population variation in throat color morph frequencies between islets was higher than that between mainland populations, and the effective population sizes on the islets were small (Ne:s < 100). Population divergence (FST) for throat color morph frequencies fell within the neutral FST-distribution estimated from microsatellite markers, and genetic drift could thus not be rejected as an explanation for the pattern. Moreover, for both comparisons among mainland-mainland population pairs and between mainland-islet population pairs, morph frequency divergence was significantly correlated with neutral divergence, further pointing to some role for genetic drift in divergence also at the phenotypic level of throat color morphs.CONCLUSIONS:Genetic drift could not be rejected as an explanation for the pattern of population divergence in morph frequencies. In spite of an expected stabilising selection, throat color frequencies diverged in the islet populations. These results suggest that there is an interaction between selection and genetic drift causing divergence even at a phenotypic level in these small, subdivided populations.
Pafilis P, Foufopoulos J, Poulakakis N, Lymberakis P, Valakos ED. Tail shedding in island lizards [Lacertidae, Reptilia]: Decline of antipredator defenses in relaxed predation environments. EvolutionEvolution. 2009;63:1262-1278.
Hurston H, Voith L, Bonanno J, Foufopoulos J, Pafilis P, Valakos E, Anthony N. Effects of fragmentation on genetic diversity in island populations of the Aegean wall lizard Podarcis erhardii (Lacertidae, Reptilia). Molecular Phylogenetics and EvolutionMolecular Phylogenetics and Evolution. 2009;52:395-405.Abstract
Landbridge islands offer unique opportunities for understanding the effects of fragmentation history on genetic variation in island taxa. The formation of islands by rising sea levels can be likened to a population bottleneck whose magnitude and duration is determined by island area and time since isolation, respectively. The Holocene landbridge islands of the Aegean Sea (Greece) were formed since the last glacial maximum and constitute an ideal system for disentangling the effects of island area, age and geographic isolation on genetic variability. Of the many reptile species inhabiting this island system, the Aegean wall lizard Podarcis erhardii is an excellent indicator of fragmentation history due to its widespread distribution and poor over-water dispersal abilities. In this study, we utilize a detailed record of Holocene fragmentation to investigate the effects of island history on wall lizard mitochondrial and nuclear microsatellite diversity. Findings show that the spatial distribution of mitochondrial haplotypes reflects historical patterns of fragmentation rather than geographic proximity per se. In keeping with neutral bottleneck theory, larger and younger islands retain more nuclear genetic variation than smaller, older islands. Conversely, there is no evidence of an effect of isolation by distance or effect of distance to the nearest larger landmass on genetic variability, indicating little gene flow between islands. Lastly, population-specific measures of genetic differentiation are inversely correlated with island area, suggesting that smaller islands exhibit greater divergence due to their greater susceptibility to drift. Taken together, these results suggest that both island area and time since isolation are important predictors of genetic variation and that these patterns likely arose through the progressive fragmentation of ancestral diversity and the ensuing cumulative effects of drift.
Pafilis P, Meiri S, Foufopoulos J, Valakos E. Intraspecific competition and high food availability are associated with insular gigantism in a lizard. NaturwissenschaftenNaturwissenschaften. 2009;96:1107-1113.Abstract
Resource availability, competition, and predation commonly drive body size evolution. We assess the impact of high food availability and the consequent increased intraspecific competition, as expressed by tail injuries and cannibalism, on body size in Skyros wall lizards ( Podarcis gaigeae ). Lizard populations on islets surrounding Skyros (Aegean Sea) all have fewer predators and competitors than on Skyros but differ in the numbers of nesting seabirds. We predicted the following: (1) the presence of breeding seabirds (providing nutrients) will increase lizard population densities; (2) dense lizard populations will experience stronger intraspecific competition; and (3) such aggression, will be associated with larger average body size. We found a positive correlation between seabird and lizard densities. Cannibalism and tail injuries were considerably higher in dense populations. Increases in cannibalism and tail loss were associated with large body sizes. Adult cannibalism on juveniles may select for rapid growth, fuelled by high food abundance, setting thus the stage for the evolution of gigantism.
Roca V, Foufopoulos J, Valakos E, Pafilis P. Parasitic infracommunities of the Aegean wall lizard Podarcis erhardii (Lacertidae, Sauria): Isolation and impoverishment in small island populations. Amphibia ReptiliaAmphibia Reptilia. 2009;30:493-503.Abstract
The Aegean wall lizard Podarcis erhardii, is widely distributed across the islands of the Aegean Sea (Greece). While there exists a relatively substantial body of knowledge on the ecology and life history of the species, the parasite communities of the taxon remain almost completely unknown. Quantifying the composition of these communities in P. erhardii is not only important for autoecological reasons, but also because inter-island comparisons of this lizard's parasite communities can shed light on the factors that structure parasite diversity in general. Here we investigate the gastrointestinal parasite communities of P. erhardii populations occurring on 16 landbridge islands of the Sporades group in the NW Aegean Sea by examining the gastrointestinal tracts of 113 lizards. In all, 8 species of helminths were found: 1 Trematode (Paradistomum mutabile), 1 Cestode (Oochoristica sp.) and 6 Nematodes (Parapharyngodon micipsae, Parapharyngodon bulbosus, Parapharyngodon echinatus, Spauligodon sp., Abbreviata sp., and Skrjabinelazia sp.). The prevalence, mean intensity, and mean abundance of infection were respectively 63.71%; 6.01 (±11.71; range 1-90); and 3.57 (±9.5; range 0-90). Brillouin's index of diversity for the Sporades was 0.048 (±0.13; range 0-0.142). These values were lower than for most other mainland and insular lacertid populations, and suggest that the investigated island populations harbor very depauperate helminth communities. The severe impoverishment of the parasite communities and the differential persistence of generalist parasite species with simple life cycles is most likely the result of a combination of insular environmental conditions (spatial and temporal isolation, arid climate, small host population sizes) and host life history characteristics (diet, simple gastrointestinal tract architecture). The paucity of parasites in these relictual island populations suggests that small reptile populations fragmented by anthropogenic activities may not be able to sustain their native parasite communities over the long term. © 2009 Koninklijke Brill NV, Leiden.
Tsasi G, Pafilis P, Simou C, Valakos ED. Predation pressure, density-induced stress and tail regeneration: A casual-nexus situation or a bunch of independent factors?. Amphibia ReptiliaAmphibia Reptilia. 2009;30:471-482.Abstract
Caudal autotomy, the self-induced tail shedding from the body, is a common defensive strategy in lizards. Tail loss is followed rapidly by regeneration, revealing the importance of a fully functional tail. Predation pressure has been traditionally correlated with autotomy performance. However there is a lack of evidence regarding the impact of predation regime on tail regeneration. Another important factor that has been neglected is the population density. Though it is well established that crowding alters various life-history traits, the impact of density on caudal regeneration remains understudied. In this paper we compared three island populations of the Aegean Wall Lizard (Podarcis erhardii) that have evolved under different levels of predation pressure: whereas the Naxos population is exposed to numerous predators the Kopries and Daskalio islet populations experience low predation pressure. To evaluate the effect of density-induced stress on caudal regeneration, lizards were treated under two conditions of housing, in single and crowded (six individuals) terraria. Tail sheding occurred prior to this treatment following a standardised method. The length of regenerated tail was recorded weekly. Regeneration rate was higher in single terraria when compared to crowded, reflecting the negative impact of crowding. However we failed to detect any statistically significant difference between single and crowded terraria in the case of Naxos. We believe that the underlying reason must be the heavy predation pressure under which rapid tail regeneration, even under unfavourable conditions, is crucial for survival. It seems that the imperious need for regeneration counteracts density-induced stress. © 2009 Koninklijke Brill NV, Leiden.
SIMOU, C. PAFILISSKELLAKOURKOULIVALAKOSPAA. Physiology of original and regenerated tails in Cycladian Wall Lizard (Podarcis erhardii). CopeiaCopeia. 2008;2008:504-509.
Pafilis P, Pérez-Mellado V, Valakos ED. Post autotomy tail activity in Balearic wall lizard, Podarcis lilfordi. NaturwissenschaftenNaturwissenschaften. 2008;95:217-221.
Pafilis P, Valakos ED. Loss of caudal autotomy during ontogeny of Balkan green lizard, Lacerta trilineata. Journal of Natural HistoryJournal of Natural History. 2008;42:409-419.Abstract
Tail loss is an effective antipredator strategy in many lizards. After loss the tail continues to thrash vigorously and may distract predators away from the escaping lizard. However, autotomy imposes energetic and survival costs (loss of lipid reserves, reduction of reproductive output, impairment of locomotor performance). Autotomy may have been lost when costs exceed benefits, while a substantial reduction or full loss may occur during ontogeny. The Balkan green lizard, Lacerta trilineata is a skilful sprinter despite its robust structure. Predation was simulated in a total of 83 individuals (48 juveniles and 35 adults). All juveniles shed their tail readily while none of the adults autotomized their tails. Postautotomyduration of movement and levels of involving metabolites in shed tails were measured. No differences were found on comparison to other Greek lacertids. These findings suggest that autotomic ability is lost ontogenetically in L. trilineata while post-autotomy energetics seems to be a conservative character.
Runemark A, Gabirot M, Bensch S, Svensson EI, Martín J, Pafilis P, Valakos ED, Hansson B. Cross-species testing of 27 pre-existing microsatellites in Podarcis gaigeae and Podarcis hispanica (Squamata: Lacertidae). Molecular Ecology ResourcesMolecular Ecology Resources. 2008;8:1367-1370.Abstract
We tested 27 microsatellite loci for cross-species amplification in the lacertids Podarcis gaigeae and Podarcis hispanica. We detected 11 and 15 polymorphic loci in the former and the latter species, respectively. In a larger sample of individuals from a single population of each species, the number of alleles ranged from five to 23 in 10 of the polymorphic loci in P. gaigeae, and between four and 13 in nine of polymorphic loci in P. hispanica. Two locus deviated from Hardy-Weinberg equilibrium in P. hispanica. Between 11 and 16 of the 27 loci also amplified successfully in three other Podarcis species. © 2008 The Authors.
Lymberakis P, Poulakakis N, Kaliontzopoulou A, Valakos E, Mylonas M. Two new species of Podarcis (Squamata; Lacertidae) from Greece. Systematics and BiodiversitySystematics and Biodiversity. 2008;6:1-12.Abstract
Recently, several works have focused on the lacertid lizards of the genus Podarcis, revealing cases of hidden diversity and paraphyly, and offering evidence that suggests the revision of the extant taxonomical arrangements within the genus. Hidden diversity and paraphyly have been shown to exist in the relationships betweentheBalkan species P. peloponnesiacaandP. erhardii as well. Herewecouple a molecular (mtDNA) dataset with a corresponding morphological one, consisting of morphometric and pholidotic characters, to check for concordance between the two. Phylogenetic analyses reinforced previous suggestions for paraphyly of P. erhardii with respect to P. peloponnesiaca.We found the variation of certain pholidotic characters concordant with the relationships inferred from partial mtDNA sequences, whereas morphometric characters were not. The latter is possibly due to greater influence of morphometric characters by environmental factors. To avoid the observed paraphyly we proceed with the description of the populations from Crete and the islet of Pori, until now designated as P. erhardii, as separate taxa at the species level.
GIOKAS S., KARKOULIS P PAFILISVALAKOSPED. Relictual physiological ecology in the threatened land snail Codrigtonia helenae: a cause for decline in a changing environment?. Acta OecologicaActa Oecologica. 2007;32.
Valakos ED, Kourkouli A, Skopeliti M, Pafilis P, Poulakakis N, Voutsas IF, Lymberakis P, Simou C, Voelter W, Tsitsilonis OE. Combining immunological and molecular data to assess phylogenetic relations of some Greek Podarcis species. Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular BiologyComparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology. 2007;147:1-10.Abstract
Most recent molecular studies revealed the phylogeny of Greek Podarcis species, which for years remained elusive, due to discordant data produced from various chromosomal, complement fixation and protein studies. In this report, we analyzed cellular immune responses of spleen derived lymphocytes from six allopatric Podarcis species encountered in Greece, by assessing two-way mixed lymphocyte reaction (MLR)-induced proliferation. On the basis of stimulation indices (S.I.) as determined from cultures set up from xenogeneic splenocytes coincubated in pairs, we generated a phylogenetic tree, fully consistent with the phylogenetic relationships of Podarcis as determined by parallel analyses basedon partial mitochondrial (mt) DNA sequences. Although the exact mechanisms triggering lymphocyte responses in lizard two-way xenogeneic MLR are not fully understood, our results show the potential use of cell-mediated immune responses as an additional approach to mtDNA analysis, for species delimitation within specific lizard taxa.
Pafilis P, Foufopoulos J, Poulakakis N, Lymberakis P, Valakos E. Digestive performance in five Mediterranean lizard species: effects of temperature and insularity. Journal of Comparative Physiology B Biochemical Systemic and Environmental PhysiologyJournal of Comparative Physiology B Biochemical Systemic and Environmental Physiology. 2007;177:49-60.Abstract
Temperature sensitivity of digestive processes has important ramifications for digestive performance in ectothermic vertebrates. We conducted a comparative analysis of temperature effects on digestive processes [gut passage times (GPTs) and apparent digestive efficiencies (ADEs)] in five lacertid lizards occurring in insular ( Podarcis erhardii, P. gaigeae ), and mainland ( P. muralis, P. peloponnesiaca, Lacerta graeca ) Mediterranean environments. GPTs were negatively correlated to temperature with mainland taxa having 10–20% longer GPTs than island taxa. In contrast to previous studies that estimate ADEs using bomb calorimetry, we compare ADEs by analyzing discrete efficiencies for lipids, sugars and proteins at three temperature regimes (20, 25, and 30°C); each of these categories produces different results. ADEs for lipids and sugars showed a monotonic increase with temperature whereas ADEs for proteins decreased with temperature. Island taxa had consistently higher ADEs than their mainland counterparts for lipids and for proteins but not for sugars. They are characterized by superior energy acquisition abilities despite significantly shorter GPTs. Their increased digestive performance relative to the mainland species appears to allow them to maximize energy acquisition in unproductive island environments where food availability is spatially and seasonally clustered.
GIOKAS, S. PAFILISVALAKOSP & ED. Seasonal ecological and physiological adaptations of the land snail Albinaria caerulea (Gastropoda, Pulmonata, Clausiliidae). Journal of Molluscan Studies Journal of Molluscan Studies. 2005;71:15-23.
Poulakakis N, Lymberakis P, Valakos E, Pafilis P, Zouros E, Mylonas M. Phylogeography of Balkan wall lizard (Podarcis taurica) and its relatives inferred from mitochondrial DNA sequences. Molecular EcologyMolecular Ecology. 2005;14:2433-2443.Abstract
Wall lizards of the genus Podarcis (Sauria, Lacertidae) comprise 17 currently recognized species in southern Europe, where they are the predominant reptile group. The taxonomy of Podarcis is complex and unstable. Based on DNA sequence data the species of Podarcis falls into four main groups that have substantial geographical conherence (western island group, southwestern group, Italian group and Balkan group). The Balkan species are divided in two subgroups: the subgroup of Podarcis taurica (P. taurica, P. milensis, P. gaigeae and perhaps P. melisellensis), and the subgroup of Podarcis erhardii (P. erhardii and P. peloponnesiaca). We addressed the question of phylogenetic relations among the species of the P. taurica subgroup encountered in Greece, as they can be inferred from partial mtDNA (cyt b and 16S) sequences. Our data support the monophyly of P. taurica subgroup and suggest that P. gaigeae, P. milensis and P. melisellensis form a clade, which thereinafter connects to P. taurica. Within the previous clade, P. gaigeae is more closely related to P. milensis than to P. melisellensis. However, the specimens of P. taurica were subdivided in two different groups. The first one includes the specimens from northeastern Greece, and the other group includes the specimens from the rest of continental Greece and Ionian islands. Because the molecular clock of the cyt b and 16 rRNA genes was not rejected in our model test, it is possible to estimate times of speciation events. Based on the splitting of the island of Crete from Peloponnisos [c. 5 million years ago (Ma)], the evolutionary rate for the cyt b is 1.55% per million years (Myr) and for the 16S rRNA is 0.46% per Myr. These results suggest that the evolutionary history of P. taurica in Greece is more complex than a single evolutionary invasion. The data analysed, stress the need for a reconsideration of the evolutionary history of Greek Podarcis species and help overcome difficulties that classical taxonomy has encountered at both the species level.
Poulakakis N, Lymberakis P, Valakos E, Zouros E, Mylonas M. Phylogenetic relationships and biogeography of Podarcis species from the Balkan Peninsula, by Bayesian and maximum likelihood analyses of mitochondrial DNA sequences. Molecular Phylogenetics and EvolutionMolecular Phylogenetics and Evolution. 2005;37:845-857.Abstract
Wall lizards of the genus Podarcis (Sauria, Lacertidae) comprise 17 currently recognized species in southern Europe, where they are the predominant novavian reptile group. The taxonomy of Podarcis is complex and unstable. Based oil DNA sequence data, the species of Podarcis falls into four main groups that have substantial geographic coherence (Western island group, southwestern group, Italian group, and Balkan Peninsula group). The Balkan Peninsula species are divided into two subgroups: the subgroup of P. taurica (P. taurica, P. milensis, P. gaigeae, and perhaps P. melisellensis), and the Subgroup of P. erhardii (P. erhardii and P. peloponnesiaca). In the present study, the question of phylogenetic relationships among the species of Podarcis encountered in the Balkan Peninsula was addressed using partial mtDNA sequences for cytochrome b (cyt b) and 16S rRNA (16S). The data support the monophyly of Podarcis and suggest that there are three phylogenetic clades: the clade A (P. taurica, P. gaigeae, P. milensis, and P. melisellensis); the clade B (P. erhardii and P. peloponnesiaca), and the clade C (P. muralis and P. sicula). By examining intraspecific relationships it was found that extant populations of P. erhardii are paraphyletic. Furthermore, subspecies previously defined on the basis of morphological characteristics do not correspond to different molecular phylogenetic clades, Suggesting that their status should be reconsidered. The distinct geographic distribution of the major clades of the phylogenetic tree and its topology Suggest a spatial and temporal sequence of phylogenetic separations that coincide with some major paleogeographic separations during the geological history of the Aegean Sea. The results stress the need for a reconsideration of the evolutionary history of Balkan Podarcis species and help overcome difficulties that classical taxonomy has encountered at both the species and subspecies level. (c) 2005 Elsevier Inc. All rights reserved.
Pafilis P, Valakos ED, Foufopoulos J. Comparative postautotomy tail activity in six Mediterranean lacertid lizard species . Physiological and Biochemical ZoologyPhysiological and Biochemical Zoology. 2005;78:828-838.Abstract
Tail autotomy, the self-induced tail separation from the body, is a common and effective antipredator mechanism in lizards. In this study, we examine the muscle energetics of tail shedding in six lacertid lizard species (Podarcis erhardii, Podarcis peloponnesiaca, Podarcis muralis, Podarcis gaigeae, Podarcis milensis, and Lacerta graeca) from the northeast Mediterranean region. Very long periods of postautotomy tail movement were demonstrated for all species (rangep6–8 min), and differences among species were not statistically significant. Postautotomy tail movement, powered by anaerobic muscle activity, resulted in a strong increase in lactate concentrations and a concomitant depletion of muscle glycogen of exhausted tails relative to resting tails. No significant differences were found in either lactate or glycogen concentrations among the species examined. Duration of movement was negatively correlated with final lactate concentrations. The lack of differentiation in postautotomy energetic physiology in this group of species that have evolved nder very different predation environments indicates that postautotomy muscle metabolism involves an overall conservative suite of characters.
Adamopoulou C, Valakos ED. Thermal ecology and activity cycle of Podarcis milensis in a sandy coastal area. Israel Journal of ZoologyIsrael Journal of ZoologyIsrael Journal of Zoology. 2005;51:39-52.Abstract
Field body temperatures (T(b)s), activity cycles, and preferred body temperatures maintained in a laboratory thermogradient (T-sel) were studied for Podarcis milensis, a small, endemic, lacertid lizard occurring in Milos Archipelago, Greece. P. milensis is active all year round; overall maximum activity level is recorded in spring, and minimum activity in winter. Daily activity patterns range from unimodal (winter) to strongly bimodal (summer). Body temperature of adults of the examined population (n = 188) averages 31.3 degrees C range 21.5-38.4 degrees C, SD 3.27 degrees C; mean monthly T(b)s are grouped together into "seasons". The species actively thermoregulates, and effectiveness of thermoregulation for the month of August is high, 0.95. The thermoregulatory behavior, microhabitat utilization, and activity cycle of this population are all discussed in the specific context of our study system: the harsh thermal environment of an insular sand dune.
MANTZIOU, G. POULAKAKISLYMPERAKISVALAKOSANDMYLONASNPEM. The inter- and intraspecific status of Aegean Mauremys rivulata (Chelonia, Bataguridae) as inferred by mitochondrial DNA sequences . Herp. J. (Lon.) Herp. J. (Lon.). 2004;14:35-45.
Poulakakis N, Lymberakis P, Antoniou A, Chalkia D, Zouros E, Mylonas M, Valakos E. Molecular phylogeny and biogeography of the wall-lizard Podarcis erhardii (Squamata: Lacertidae). Molecular Phylogenetics and EvolutionMolecular Phylogenetics and Evolution. 2003;28:38-46.Abstract
Erhard s wall lizard, Podarcis erhardii (Sauria: Lacertidae), is highly diversified in Greece and especially in the southern Aegean region. Out of the 28 recognized subspecies, 27 are found in Greece from the North Sporades island-complex in the North Aegean (grossly south of the 39th parallel) to the island of Crete in the South. The species exhibits great morphological and ecological plasticity and inhabits many different habitats from rocky islets and sandy shores to mountaintops as high as 2000m. By examining intraspecific variability at a segment of the mitochondrial gene cytochrome b we have found that that extant populations of P. erhardii are paraphyletic. Furthermore, we have found that subspecies previously defined on the basis of morphological characteristics do not correspond to different molecular phylogenetic clades, so that their status should be reconsidered. The DNA based biogeographical and phylogenetic history of Podarcis in Southern Greece is congruent with available paleogeographic data of the region, which supports the view that DNA sequences may be a useful tool for the study of palaeogeography.
DIMAKI, M. VALAKOSLEGAKISCHONDROPOULOSEDA &. Morphometric analysis of the African chamaeleon Chamaeleo africanus laurenti ,1768 from southern Peloponnese, Creece. Isr. J. of Zool.Isr. J. of Zool. 2000;46:231-237.
Chondropoulos B, Fraguedakis S, Tsekoura N, Tryfonopoulos G, Pafilis P, Valakos ED. Contribution to the study of the genetic variability and taxonomic relationships among five lizard species of the family Lacertidae from Greece. Belgian Journal of ZoologyBelgian Journal of Zoology. 2000;130:37-41.Abstract
The present study examines the genetic variability and the taxonomic relationships among five lacertid species, i.e. Podarcis taurica, P. milensis, P. peloponnesiaca, Lacerta graeca and Algyroides moreoticus, representing the three main genera of this family in Europe. The last four of the above species are endemic to Greece and three of them live sympatrically in Peloponnisos. These relationships were studied by allozyme analysis. Of the loci analyzed, the Mpi-1 locus was found to be a convenient molecular marker for discrimination of the genera Podarcis (allele a), Lacerta (allele b) and Algyroides (allele c). The values of Nei’s genetic distances between the examined species ranged from 0.025 to 0.484. According to the UPGMA-dendrogram plotted using the Nei’s genetic distances, two species groups are formed indicating that the genera Lacerta and Algyroides show a stronger relationship to one another than either does to Podarcis. These results are in agreement with DNA sequence data but are not in accordance with previous electrophoretic and immunological studies, which suggest that Lacerta is more closely related to Podarcis than to Algyroides. The studied Podarcis taxa were found to be close relatives (Nei’s distances <0.18), especially P. taurica and P. milensis. These values are lower than those usually given in the literature for the distinction of lacertid species.
Chondropoulos B, Fraguedakis S, Tsekoura N, Tryfonopoulos G, Pafilis P, Valakos E. Contribution to the study of the genetic variability and taxonomic relationships among five lizard species of the family Lacertidae from Greece. Belgian Journal of ZoologyBelgian Journal of Zoology. 2000;130:37-41.
Adamopoulou C, Valakos E. Small clutch size in a Mediterranean endemic lacertid (Podarcis milensis). CopeiaCopeia. 2000;2000:610-614.Abstract
The reproductive strategy of Podarcis milensis exhibits some peculiarities when compared with other congeners. Males and females attain sexual maturity at a minimum body size of 47 and 42 mm SVL, respectively, both at an age of about one year. Podarcis milensis has a very small clutch size, with a mean of 1.73 and a range of 1-3 eggs, and produces multiple clutches annually. Both sexes exhibit a prolonged reproductive period extending from January to August.
Dimaki M, Valakos ED, Legakis A. Variation in body temperatures of the African Chameleon Chamaeleo africanus Laurenti, 1768 and the Common Chameleon Chamaeleo chamaeleon (Linnaeus, 1758). Belgian Journal of ZoologyBelgian Journal of Zoology. 2000;130:89-93.Abstract
Data on the thermal ecology of the African Chameleon Chamaeleo africanus Laurenti, 1768 and the Common Chameleon Chamaeleo chamaeleon (Linnaeus, 1758) are reported from Greece. In the field the Tb values ranged from 10.4°C to 31.6°C for C. africanus and 23.5°C to 31°C for C. chamaeleon. There was a significant correlation between Tb and Ta in spring and summer for both species. There was also a significant correlation between Tb and Ts only in the spring and only for C. africanus. Cloacal temperatures differed significantly between spring and summer and so did substrate temperatures and air temperatures. As the months became hotter the animals reached higher temperatures. In a laboratory temperature gradient, the preferred body temperatures of C. africanus and C. chamaeleon were measured and compared with field body temperatures. The preferred body temperature in the laboratory gradient ranged from 26.0°C to 36.0°C for C. chamaeleon and from 25.0°C to 35.0°C for C. africanus. The mean Tb for C. africanus in the laboratory was 31°C while for C. chamaeleon it was 31.6°C. The results indicate that both chameleon species are thermoconformers. Cloacal temperatures differed significantly between the two species in the field but not in the laboratory. There was no difference between the Tb of the two sexes, both in the field and in the laboratory.
VALAKOS, E. D. PMARAGOUMYLONASM. Geographical distribution: Podarcis erhardii. SSAR Herp. RevSSAR Herp. Rev. 1999;30:52-53.
Maragou P, Chondropoulos B, Valakos ED. Comparative data on reproduction in Podarcis erhardii, Podarcis peloponnesiaca, and Podarcis taurica (Reptilia, Sauria, Lacertidae). Israel Journal of Zoology. 1999;454:487-496.Abstract
Variation in the reproductive traits of Greek populations of Podarcis erhardii, P. peloponnesiaca, and P. taurica living in similar habitats along the same latitude was examined. Female body size, clutch size, and egg volume were determined. In all three species, clutch size was positively correlated with maternal body size. P. erhardii appears to modulate its reproductive effort by means of variation in both egg size and number. On the other hand, egg size in P. peloponnesiaca and P. taurica has probably been optimized, and an increase in reproductive effort would result in the production of a larger number of eggs.
Adamopoulou C, Valakos ED, Pafilis P. Summer diet of Podarcis milensis, Podarcis gaigeae and Podarcis erhardii (Sauria: Lacertidae). Bonn Zoological Bulletin. 1999;48:275-282.
ADAMOPOULOU C., VALAKOS LEGAKISE & A. Notes on the diet and reproduction of the Cyclades Blunt-nosed Viper Macrovipera schweizeri (Werner, 1935). Herpetozoa Herpetozoa. 1997;10:173-175.
KASAPIDIS, P. PROVATIDOUMARAGOUVALAKOSSPE. Neue Daten ϋber die Herpetofauna von Lesbos ( Αgaische Inseln Griechenland) und einige biogeographische Bemerkungen ϋber die Inseln des nordostlichen agaischen Archipels. . SalamandraSalamandra. 1996;32:171-180.
Maragou P, Valakos ED, Giannopoulos Z, Stavropoulou A, Chondropoulos B. Spring aspect of feeding ecology in Podarcis peloponnesiaca (Bibron & Bory, 1933). HerpetozoaHerpetozoa. 1996;9:105-110.Abstract
The stomach contents of 108 specimens of Podarcis peloponnesiaca (BlBRON & BORY, 1833) were examined and the results of the analysis are discussed together with prey availability data. The animals were sampled during the spring months March to May when the activity of the lizards and their prey is at its peak. According to the results of the present study, P. peloponnesiaca feeds mainly on arthropods. Imaginai Coleoptera, Diptera, insect larvae, and spiders were the most frequently encountered prey in the lizard's environment. The same taxa were found to be numerically predominant in the stomachs of P. peloponnesiaca.
MYLONAS, M. BOTSARISSOURDISVALAKOSIIE. ). On the Development, habitat selection and Taxonomy of Helix (Jacosta) siphnica Kobelt, 1983 (Gastropoda, Helicellinae). Zool. J. Lin. SociZool. J. Lin. Soci. 1995;115:347-357.
VALAKOS, E. D. PMARAGOUMYLONASM. Geographical distribution: Podarcis erhardii. SSAR Herp. RevSSAR Herp. Rev. 1995;26:155.
Mylonas VM & E. Biogeographical analysis of the herpetofauna of the Greek islands. XXXI Congres-Assemblee Pleniere de la C.I.E.S.M. 1988;31:131.