Aurora M. Castilla

Altitudinal variation of the thermal biology and running performance in the lizard Podarcis tiliguerta

SummaryWe studied, in the field and laboratory, aspects of the thermal biology in two populations of the lizard Podarcis tiliguerta along a 1450 m altitudinal gradient. Body temperatures (Tb) at high altitudes average lower, are more variable, but are more elevated above environmental temperatures than at sea level. Lizards partially reduced the impact of altitudinal changes in thermal loads through presumable subtle behavioural adjustments. A comparison of the thermal preferences in the laboratory, the maximal operative temperatures predicted from a biophysical model, and the activity Tbs at both sites, indicates that the main response to changing environmental conditions is an active shift in thermoregulatory set points. Integration of field Tbs and laboratory data on temperature specific sprint speeds, predicts that the mountainous lizards experience reduced running abilities that are especially acute in the early morning. Despite this impairment of running performance, the thermal sensitivity of running speed has not evolved to match the Tbs experienced by both populations. This result supports the view that the thermal physiology of this lizard is evolutionarily conservative, but the lack of information on the relation between running performance and fitness components impedes rejection of alternative hypotheses.

A Comparative Study of Preferred Body Temperatures and Critical Thermal Tolerance Limits among Populations of Zootoca vivipara (Squamata: Lacertidae) along an Altitudinal Gradient

We compared preferred body temperatures, critical thermal minima, and maxima, and toler- ance ranges among four populations of Zootoca vivipara (formerly Lacerta vivipara) distributed along an altitudinal gradient (250-1450 m) to examine whether different thermal environments have induced a change in these thermal characteristics. Lizards in all populations had similar preferred body temperatures and critical thermal limits, suggesting that acclimation or adaptation of these traits to different thermal environ- ments did not occur. Subadult females and gravid females preferred lower body temperatures than non- gravid females and subadult and adult males. Preferred body temperatures differed among individuals of the same age and sex within a particular population. In contrast to the negligible among-population vari- ation, preferred body temperatures varied considerably within populations in Z. vivipara.

Thermal biology, microhabitat selection, and conservation of the insular lizard Podarcis hispanica atrata

SummaryWe studied aspects of the thermal biology and microhabitat selection of the endangered lizard Podarcis hispanica atrata during autumn in the field and laboratory. Body temperatures (Tb) of active lizards were within a narrow range, were largely independent of ambient temperatures, and exhibited little diel variation. Activity Tbs largely coincided with the selected temperatures maintained in a laboratory thermogradient and with Tbs that maximize running performance. Alternation of basking with other activities and shuttling between sun and shade were obvious aspects of thermoregulatory behaviour. Lizards shifted microhabitat use throughout the day. During early morning and late afternoon, basking lizards were restricted to rocky sites surrounded by shrubs. Near midday lizards used a wider array of microhabitats, and many moved in open grassy sites. Juveniles maintained lower activity Tbs, had lower selected temperatures, and basked less frequently than the adults. Juveniles occupied open grassy patches more often than the adults. We discuss the relevance of our results for the conservation of this extremely rare lizard and the management of its habitats.

Diet composition of the lizard Lacerta lepida in central Spain

-We studied diet composition of Lacerta lepida in a sample of 325 specimens from central Spain. This large lacertid lizard feeds predominantly on Coleoptera, but also consumes other arthropods, snails, small vertebrates, and some plant material. Composition of the animal fraction of the diet and trophic diversity were virtually identical in adult males and females. Juveniles fed upon a restricted number of prey types which were small in size, whereas adults consumed a large number of prey taxa, covering a wider range of prey sizes. Trophic segregation among individual lizards was highest in the smaller size classes. The incidence of plant material increased with lizard size and was highest in males, but it never represented a substantial fraction of the total diet. The contribution of small vertebrates to total prey numbers also increased with lizard body size. Our results indicate that vertebrates are of marginal numerical importance to the diet of L. lepida. Most lizards feed primarily on arthropods, although some species have adopted a diet consisting mainly of molluscs, plant material or small vertebrates (see Greene, 1982). Insectivorous lizards are often opportunistic feeders, eating any suitable sized arthropods. Hence, diet composition has been shown to exhibit seasonal or (micro)geographic variation, in response to a shift in prey availability which is either presumed (e.g., Avery, 1966; Mou and Barbault, 1986; Arnold, 1987) or documented (e.g., Ballinger and Ballinger, 1979; Stamps et al., 1981; 4 Present Address: University of Antwerp (U.I.A.), Department of Biology, Universiteitsplein 1, B-2610 Wilrijk, Belgium. Mou, 1987). Body size is another factor that influences prey choice and diet composition (Pough, 1973). Although most evidence for a relation between body size and dietary composition derives from interspecific comparisons, ontogenetic changes in prey choice within single lizard species have been described (see Pough, 1973; Greene, 1982). European lizards of the family Lacertidae are basically insectivorous, although some forms occasionally eat other invertebrates, small vertebrates or plants (see Arnold, 1987). Lacerta lepida, the largest European lacertid (adult snoutvent-length 140-220 mm), is a diurnal, heliothermic, ground-dwelling lizard that is found in a variety of mediterranean habitats throughout most of Spain and Portugal, in southern 30 This content downloaded from 207.46.13.133 on Fri, 22 Jul 2016 06:04:36 UTC All use subject to http://about.jstor.org/terms DIET COMPOSITION IN LACERTA LEPIDA France and extreme northwest Italy. Diet composition, one of the best studied features of the biology of this lizard, has been treated by a large number of authors (Peters, 1962; Valverde, 1967; Mellado et al., 1975; Escarre and Vericad, 1981; Perez-Mellado, 1981; Bas, 1982; Seva, 1982; Bischoff et al., 1984; Brafia, 1984; Mateo, 1988; and Busack and Visnaw, 1989). However, most studies were based on small samples, and made no distinction between lizard sex or size classes. Lacerta lepida experiences a >100-fold increase in body mass during its ontogeny (from 2 to 280 g), and the sexes differ notably in maximum body size and head dimensions (Castilla, 1989). We hypothesized that such morphological differences might induce diverging prey choices. One of the most controversial aspects of this lizards feeding ecology is the common belief that it preys extensively on small vertebrates, particularly eggs and chicks of the Redlegged Partridge (Alectoris rufa), an important game bird in Spain. Although published studies do not support this opinion, one could argue that the dietary contribution of vertebrate prey might have been underestimated due to the examination of small numbers of lizards from re-

Predation and spatial distribution of the lizard Podarcis hispanica atrata: an experimental approach

This study reports on an experiment designed to quantify potential predation by birds on the lizard Podurcis hispanica atratu in the Columbretes islands (Castellbn, Spain). We used plasticine replicas to examine predation risk of replicas as a function of proximity to vegetation and to potential predators, and to investigate the seasonal variation in patterns of predation. Predation on replicas was very high and intensive within only four days, and differed between study areas and seasons. Predation was more intense when replicas were closer to nests of gulls and far from vegetation. The Yellow-legged Gull (Lurus cachinnans michaellis) was identified as the major species responsible for predation on lizard replicas.

Observations on the natural history, present status, and conservation of the insular lizard Podarcis hispanica atrata on the Columbretes archipelago, Spain

The world range of the lizard Podarcis hispanica atrata is retricted to the Columbretes archipelago in the Mediterranean. We examined its actual distribution, abundance and some aspects of its natural history. Lizards were found in four islets (combined area c. 20 ha). Densities on the largest islet (13 ha) are high (> 600 lizards/ha), at least in favourable habitats. Population sizes on the smaller islets are extremely small (< 200 individuals). A considerable number of juvenile lizards was found in all populations. We report new information on body length distribution, sexual dimorphism, tail break frequency, escape behaviour, and diet composition. Recommendations for the conservation of this lizard and the improvement of its habitat are given and discussed in relation to landscape management programmes.

Chemosensory predator recognition in the lizard Podarcis hispanica: Effects of predation pressure relaxation

We compared the behavior of two subspecies ofPodarcis hispanica lizards in cages that had been chemically marked by a saurophagous snake, the viperVipera latastei. One of the subspecies (P.h. atrata) has experienced a relaxation from predation pressure by this viper, as snakes were eradicated from the island it inhabits over 100 years ago. Nevertheless, individuals fromP.h. atrata responded to the snakes chemicals similarly to individuals from a population ofP.h. hispanica, currently sympatric withV. latastei. Lizards exhibited more stress-indicating behaviors (foot shakes, tail vibrations, sudden starts), became less mobile, and tongue-flicked more while moving in a snake-inhabited terrarium than when in a clean, unfamiliar terrarium.

Field body temperatures and thermoregulatory behavior of the high altitude lizard, Lacerta bedriagae

Many species of lizards are known to maintain relatively high and constant body temperatures (Avery, 1982; Huey, 1982). Their abilities to do so depend largely on regulatory behaviors that alter heat exchange with the environment and on the thermal conditions within their habitats. Ectotherms living at high altitudes (and latitudes) offer unique opportunities to study thermoregulatory responses to the rather unfavorable and strongly variable thermal characteristics of these regions. High altitude lizards often exhibit lower and more variable activity body temperatures, and/or thermoregulate less precisely than conspecific or congeneric populations living at lower elevations (Brattstrom, 1965; Hertz and Nevo, 1981; Vial, 1984; Crowley, 1985). We report here results of a short-term study on field body temperatures and aspects of thermoregulatory behavior of the lizard Lacerta bedriagae. This mediumsized lizard (adult male body size = 66-84 mm, mass = 7-14 g; adult female body size = 66-80 mm, mass = 7-11 g) is endemic to the Mediterranean islands Corsica and Sardinia, where its distribution is usually retricted to altitudes >1000 m (Schneider, 1984 reviews information on the habits of this poorly known species). We hypothesized that this lizard, living in an environment characterized by low and variable ambient temperatures, would be active over a relatively wide range of body temperatures. Our main aim therefore was to examine changes in body temperature and thermoregulatory behavior in relation to diel variations in the thermal environment.

Reproductive and Fat Body Cycles of the Lizard, Lacerta lepida, in Central Spain

We studied the annual reproductive and fat body cycles of the oviparous lizard Lacerta lepida in central Spain. Testicular recrudescence started in late summer and testes attained their maximal sizes during the following spring. Females exhibited ovarian growth during spring and most oviposited in July. Fat bodies of males were smallest during the mating period. Female fat body volumes declined during vitellogenesis. No significant decline of lipid stores was detected during the hibernation period (October-March).

Conservation genetics of insular Podarcis lizards using partial cytochrome b sequences

Sequence data derived from a 306 bp fragment of mitochondrial cytochrome b and molecular variance estimates were used to investigate the genetic population structure of the endangered and endemic lizard Podarcis atrata of the Columbretes archipelago (Mediterranean, Spain). Our results show a very high and significant among‐population genetic differentiation. FST values and phylogenetic analyses confirm the evolutionary distinctiveness of P. atrata populations, suggesting that the populations of these islands deserve special protection measures. The populations of the two islands Columbrete Grande and Mancolibre are less differentiated than those of Foradada and Lobo, and seem to have retained mainland haplotypes. This situation needs further attention as the origin of the mainland haplotypes is still unclear. If they are a result of recent introductions from mainland specimens, then they may represent a threat to the endemic lizards of the Columbretes islands.