Podarcis Melisellensis Research Articles

Functional and ecological relevance of intraspecific variation in body size and shape in the lizard Podarcis melisellensis (Lacertidae)

Within populations, individual animals may vary considerably in morphology and ecology. The degree to which variation in morphology is related to ecological variation within a population remains largely unexplored. We investigated whether variation in body size and shape among sexes and age classes of the lizard Podarcis melisellensis translates in differential whole-animal performance (sprint speed, bite force), escape and prey attack behaviour in the field, microhabitat use and diet. Male and female adult lizards differed significantly in body size and head and limb proportions. These morphological differences were reflected in differences in bite strength, but not in sprint speed. Accordingly, field measurements of escape behaviour and prey attack speed did not differ between the sexes, but males ate larger, harder and faster prey than females. In addition to differences in body size, juveniles diverged from adults in relative limb and head dimensions. These shape differences may explain the relatively high sprint and bite capacities of juvenile lizards. Ontogenetic variation in morphology and performance is strongly reflected in the behaviour and ecology in the field, with juveniles differing from adults in aspects of their microhabitat use, escape behaviour and diet. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 94, 251-264.

4.P12. Testosterone and performance in the different colour morphs of the Dalmatian wall lizard

4.P12. Testosterone and performance in the different colour morphs of the Dalmatian wall lizard

Morphology, performance, behavior and ecology of three color morphs in males of the lizard Podarcis melisellensis

Males of a Croatian population of the lacertid lizard Podarcis melisellensis exhibit a striking polymorphism, with coloration of the throat and abdomen ranging from completely white, to yellow or orange. In a first attempt to explore the potential ecological and evolutionary significance of this polymorphism, we compared the three forms of males in aspects of their morphology, whole-animal performance, behavior, and ecology. Orange males are, on average, larger in snout-vent length and have disproportionately larger heads than either white or yellow males. This is reflected in orange males having higher bite force capacity and theoretically an increased access to harder prey. Residual limb length, maximal sprint speed and maximal exertion do not differ among color morphs. Body temperatures in the field are similar in the three morphs, but yellow males are caught at sites with slightly higher air temperatures than are orange and white males. Behavioral observations show no differences in time budgets or in the timing of activities among morphs. Microhabitat use is also similar in the three color morphs, but orange males were more often initially seen on rocky substrates. Our findings suggest that the observed polymorphism likely does not originate from a divergence in niche or use of resources, but possibly reflects an underlying polymorphism in mating tactics.

Mitochondrial phylogeography of the Dalmatian wall lizard, Podarcis melisellensis (Lacertidae)

A 903 bp section of the mitochondrial cytochrome b gene was sequenced from 73 specimens of Podarcis melisellensis collected at 52 localities distributed over the major part of the species’ range. In addition, parts of the 12S (about 470 bp) and 16S rRNA (about 500 bp) genes were analysed for 11 representative samples leading to a congruent phylogeny. Our study includes representatives of all 20 subspecies recognized today. The phylogenetic analysis of the sequence data revealed three main clades: mainland with nearby islands, Vis archipelago, and Lastovo archipelago. The degree of mitochondrial DNA divergence among these clades suggests a separation of the respective population groups during the earliest Pleistocene. The phylogenetic pattern observed within the species is in sharp contrast to the actual taxonomic division into subspecies. A correlation between genetic diversity of P. melisellensis populations and paleogeography of the regions they inhabit is discussed.

Relationships between head size, bite force, prey handling efficiency and diet in two sympatric lacertid lizards

Summary Relationships between morphology, bite force capacity, prey handling efficiency and trophic niche were explored in two sympatric species of lacertid lizards, Podarcis melisellensis (Braun 1877) and Lacerta oxycephala Duméril & Bibron 1839. Head shape showed little variation, but head size (absolute and relative to snout–vent length, SVL) differed between species and sexes. Males have larger heads than females, both absolute and relative to their SVL. In absolute terms, male P. melisellensis have larger heads than male L. oxycephala, but the reverse case was true for the females. Relative to SVL, L. oxycephala have larger heads than P. melisellensis. Bite force capacity was estimated by having the lizards bite on two metal plates, connected to a piezoelectric force transducer. Differences in maximal bite force between species and sexes paralleled differences in absolute head size. Differences in body size and head size explain the higher bite force of males (compared with females), but not the higher bite force of P. melisellensis (compared with L. oxycephala). Among individual lizards, bite force correlated with body size and head size. Prey handling efficiency, estimated by the time and number of bites needed to subdue a cricket in experimental conditions, also showed intersexual and interspecific variation. This variation corresponded to the differences in maximal bite capacity, suggesting that bite force is a determining factor in prey handling. Among individual lizards, both estimates of handling efficiency correlated with maximal bite force capacity. Faecal pellet analyses suggested that in field conditions, males of both sexes select larger and harder prey than females. There was no difference between the species. The proportion of hard‐bodied and large‐sized prey items found in a lizard's faeces correlated positively with its bite force capacity. It is concluded that differences in head and body size, through their effect on bite force capacity, may affect prey selection, either directly, or via handling efficiency.

Micro-scale differences in thermal habitat quality and a possible case of evolutionary flexibility in the thermal physiology of lacertid lizards.

We studied the thermal ecology of the lacertid lizards Lacerta oxycephala and Podarcis melisellensis on the Adriatic island of Vis (Croatia) during summer. These species obviously differ in microhabitat use: L. oxycephala climbs on rocks and stone walls, whereas P. melisellensis is mainly ground-dwelling in vegetation. Since theoretical considerations predict a difference in thermal quality between the species' microhabitats, this system seems to present a good opportunity to test the influence of thermal microhabitat quality on body temperature, thermoregulatory behaviour and evolution of thermal characteristics. Data on thermoregulatory behaviour, body temperatures (T b) and habitat quality were collected in the field and selected temperatures (T sel) were estimated in a laboratory thermogradient. Accuracy and effectiveness of thermoregulation were quantified. Thermoregulatory behaviour consisted of timing of activity, selection of places in full sun and near sun-shade transitions, and basking. As predicted, L. oxycephala occupied the microhabitat with the lower thermal quality and had on average a lower T b. However, L. oxycephala also selected lower temperatures in the experimental thermogradient. Thus, if T sel can be regarded as the thermoregulatory target, both species proved to be accurate and effective thermoregulators. These results corroborate the "labile view" on the evolution of thermal physiology: both L. oxcephala and P. melisellensis appear to be adapted to their respective thermal microhabitat. This is a surprising conclusion, since earlier studies have found the thermal characteristics of Lacertidae to be evolutionarily rigid.

Constraints on Temperature Regulation in Two SympatricPodarcisLizards during Autumn

We studied the impact of restrictions by the thermal environments on body temperatures (Tbs) and microhabitat use of the lacertid lizards Podarcis melisellensis and Podarcis muralis in a Mediterranean area (Croatia) during autumn. The thermal conditions at available microhabitats were assessed with copper models that measured the operative temperatures (Te) at different sites. We estimated the thermal suitability of microhabitats by quantifying the extent of similarity between the Tes and the range of selected temperatures (i.e., the Tbs that lizards maintain in zero-cost conditions in a laboratory thermogradient; Tsel). Both species maintained, throughout most of day, Tbs that were on average 2–4 C below both Tsel and the Tbs recorded in the field during summer. Nevertheless, the Tbs measured during autumn were in the upper range of available Tes and were much closer to the Tsel than were the Tes. In addition, lizards were most often observed in the warmest microhabitats and were often seen basking. These results indicate that lizards were actively thermoregulating. The Te measurements show that lizards encounter suitable thermal conditions (i.e., where Tes is within Tsel) in only a restricted subset of the available microhabitats and during only a relatively short period of the day. Thus, lizards are constrained to maintain relatively low Tbs during autumn by the generally low available Tes. Although lizards were clearly thermoregulating, they appeared to accept lower Tbs during activity in autumn than in summer. A possible reason for this seasonal shift in activity Tbs is that achievement of higher Tbs during autumn is only feasible by confining activities to some specific microhabitats, which may severely constrain other behaviors, such as foraging.

On the evolutionary pathway of parental care in mouth–brooding cichlid fishes

Evolutionary theory predicts that differences in parental care patterns among species arose from interspecific differences in the costs and benefits of care for each sex. In Galilee St Peter9s fish, Sarotherodon galilaeus (Cichlidae), male care, female care and biparental care all occur in the same population. We exploit this unusual variability to isolate conditions favouring biparental versus uniparental mouth–brooding by males or females. We first review a game–theoretic model of parental care evolution, predictions of which we test experimentally in this paper. Manipulations of the operational sex ratio show that males and females desert their offspring more frequently when the costs of care are high (in terms of lost mating opportunities). Breeding trials with males of different sizes show that small fathers desert more frequently than large fathers. We attribute this to the associated difference in the fitness benefit of biparental care relative to female–only care. Our experimental results confirm that in St Peter9s fish the probability of caring is determined facultatively according to current conditions at each spawn. The experiments and model together suggest that interspecific variation in remating opportunities and clutch size may be responsible for differences in care patterns within the sub–family Tilapiini. Our results support the hypothesis that biparental mouth–brooding was the ancestral state of both male and female uniparental mouth–brooding in cichlid fishes.