Mainland Lizards Research Articles

Proximate Drivers of Population-Level Lizard Gut Microbial Diversity: Impacts of Diet, Insularity, and Local Environment.

Diet has been suggested to be an important driver of variation in microbiota composition in mammals. However, whether this is a more general phenomenon and how fast changes in gut microbiota occur with changes in diet remains poorly understood. Forty-nine years ago, ten lizards of the species Podarcis siculus were taken from the island of Pod Kopište and introduced onto the island of Pod Mrčaru (Croatia). The introduced population underwent a significant dietary shift, and their descendants became omnivorous (consuming up to 80% plant material during summer). Variation in their gut microbiota has never been investigated. To elucidate the possible impact on the gut microbiota of this rapid change in diet, we compared the microbiota (V4 region of the 16S rRNA gene) of P. siculus from Pod Mrčaru, Pod Kopište, and the mainland. In addition, we explored other drivers of variation in gut microbiota including insularity, the population of origin, and the year of sampling. Alpha-diversity analyses showed that the microbial diversity of omnivorous lizards was higher than the microbial diversity of insectivorous lizards. Moreover, omnivorous individuals harbored significantly more Methanobrevibacter. The gut microbial diversity of insectivorous lizards was nonetheless more heterogeneous. Insectivorous lizards on the mainland had different gut microbial communities than their counterparts on the island of Pod Kopište. Bacillus and Desulfovibrio were more abundant in the gut microbiota from insular lizards compared to mainland lizards. Finally, we showed that the population of origin was also an important driver of the composition of the gut microbiota. The dietary shift that occurred in the introduced population of P. siculus has had a detectable impact on the gut microbiota, but other factors such as insularity and the population of origin also contributed to differences in the gut microbial composition of these lizards, illustrating the multifactorial nature of the drivers of variation in gut microbiota. Overall, our data show that changes in gut microbiota may take place on ecological timescales. Yet, diet is only one of many factors driving variation in gut microbiota across populations.

Fixation of genetic variation and optimization of gene expression: The speed of evolution in isolated lizard populations undergoing Reverse Island Syndrome.

The ecological theory of island biogeography suggests that mainland populations should be more genetically divergent from those on large and distant islands rather than from those on small and close islets. Some island populations do not evolve in a linear way, but the process of divergence occurs more rapidly because they undergo a series of phenotypic changes, jointly known as the Island Syndrome. A special case is Reversed Island Syndrome (RIS), in which populations show drastic phenotypic changes both in body shape, skin colouration, age of sexual maturity, aggressiveness, and food intake rates. The populations showing the RIS were observed on islets nearby mainland and recently raised, and for this they are useful models to study the occurrence of rapid evolutionary change. We investigated the timing and mode of evolution of lizard populations adapted through selection on small islets. For our analyses, we used an ad hoc model system of three populations: wild-type lizards from the mainland and insular lizards from a big island (Capri, Italy), both Podarcis siculus siculus not affected by the syndrome, and a lizard population from islet (Scopolo) undergoing the RIS (called P. s. coerulea because of their melanism). The split time of the big (Capri) and small (Scopolo) islands was determined using geological events, like sea-level rises. To infer molecular evolution, we compared five complete mitochondrial genomes for each population to reconstruct the phylogeography and estimate the divergence time between island and mainland lizards. We found a lower mitochondrial mutation rate in Scopolo lizards despite the phenotypic changes achieved in approximately 8,000 years. Furthermore, transcriptome analyses showed significant differential gene expression between islet and mainland lizard populations, suggesting the key role of plasticity in these unpredictable environments.

Chemosensory deficiency may render island-dwelling lizards more vulnerable to invasive predators

AbstractNewly introduced predators constitute a major threat to prey populations worldwide. Insular prey animals in particular often do not succeed in overcoming their naivety towards alien predators, making them specifically vulnerable. Why this is the case remains incompletely understood. Here, we investigate how the ability to detect and respond to predator chemical cues varies among populations of the Dalmatian wall lizard, Podarcis melisellensis. Lizards were sampled from five locations in south-eastern Croatia (one mainland location and four islands) that varied in the composition of their predator community. We observed the lizards’ behaviour in response to chemical cues of native saurophagous snakes (the Balkan whip snake, Hierophis gemonensis, and eastern Montpellier snake, Malpolon insignitus) and an introduced mammalian predator (the small Indian mongoose, Herpestes auropunctatus – a species held responsible for the loss of numerous insular reptile populations worldwide). Mainland lizards showed elevated tongue-flick rates (indicative of scent detection) as well as behaviours associated with distress in response to scents of both native and introduced predators. In sharp contrast, island lizards did not alter their behaviour when confronted with any of the predator cues. Alarmingly, even lizards from islands with native predators (both snakes and mammals) and from an island on which mongooses were introduced during the 1920s were non-responsive. This suggests that insular populations are chemosensorily deprived. As failure at the predator-detection level is often seen as the most damaging form of naivety, these results provide further insight into the mechanisms that render insular-living animals vulnerable to invasive species.

Genetic differentiation predicts body size divergence between island and mainland populations of common wall lizards (Podarcis muralis)

AbstractSmall-bodied vertebrates sometimes evolve gigantism on islands, but there is a lack of consistent association with ecological factors or island characteristics. One possible reason is that, even if the ecological conditions are right, body size might fail to diverge on islands that were isolated recently or if there is gene flow between islands and the mainland. We studied body size, ventral colour polymorphism and genetic structure across nine islands and adjacent mainland populations of common wall lizards (Podarcis muralis) off the western coast of France. Population genetic data suggested that island populations might have maintained gene flow after their geographical isolation from the mainland. Island lizards were larger and heavier than mainland lizards on average, but the extent of gigantism varied substantially between islands. Island size and distance from the mainland were poor predictors of body size, but lizards from populations that were highly genetically differentiated from the mainland were larger than lizards from less differentiated populations. Colour morphs that were rare on the mainland tended to be more common on islands. We propose that genetic isolation or bottlenecks promote body size evolution in island lizards, which makes it challenging to identify ecological causes of island gigantism without complementary genetic information.

Phylogeny, biogeography and island effect drive differential evolutionary signals in mainland and island lizard assemblages

Phylogeny, biogeography and island effect drive differential evolutionary signals in mainland and island lizard assemblages

Differences in growth rate, body condition, habitat use and food availability between island and mainland lizard populations ofAnolis nebulosusin Jalisco, Mexico

Abstract:Lizards of the genusAnolishave been widely studied, however, little is known about the effects of environmental seasonality, food availability and geographic isolation on body condition, growth rate and habitat use of lizards. The existence of an insular and a continental population ofAnolis nebulosus(clouded anole), separated by only 0.47 km, represents an ideal opportunity to address this topic. We compared seasonal fluctuations in food availability (arthropod density) for anoles, as well as body condition, growth rate and habitat use in the two populations. Food availability throughout the year was sampled every 2 mo by trapping arthropods at each site. Lizards were also monitored and measured every 2 mo by surveying three quadrats in each site over 2 y giving a total of 30 visits for each quadrat. Results suggested that composition and density of food supply was similar for the two populations. Nevertheless, food supply responded to seasonality of rainfall, with an increase of 1.5 times during the rainy season. Despite similarity in food availability, insular anoles had body condition that was 5–10 times better, with growth rate twice as fast, and used similar perches. The role of predation, and inter- and intraspecific competition are discussed as possible drivers.

Population abundance, size structure and sex-ratio in an insular lizard

Estimating population size and understanding its variation is a fundamental, yet complicated, aim of many ecological studies. We considered the problem of estimating spring and autumn population abundance, size-dependent population structure and sex-ratio of the endemic Balearic Lizard, Podarcis lilfordi from a three occasions capture-recapture study. We used a Bayesian formulation of individual covariate models to incorporate individual sex, size and trap-response. We first considered a set of simulated data with a medium-to-low probability of recapture and individual recapture heterogeneity to evaluate potential problems in model fitting and selection. Results from simulated data indicated a low performance in parameter estimation and model selection when probability of detection was low (0.15–0.30). We found a negative permanent trap response and a positive effect of size on detection probability in the spring survey but not in the autumn one. The estimated mean densities varied from about 800 to 1000lizardsha−1, a high value when comparing with mainland lizard populations. The observed increase in abundance was probably due to a drop in territorial behaviour and the immigration of females into the area sampled. As a consequence, sex-ratio changed from nearly even in June (mean posterior, 95%CRI; 0.928, 0.676–1.167) to a female-skewed population in October (0.612, 0.478–0.772).

The impact of insularity on the thermoregulation of a Mediterranean lizard

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.

The island syndrome in lizards

AbstractAimIslands are thought to promote correlated ecological and life‐history shifts in species, including increased population density, and an infrequent production of few, large, offspring. These patterns are collectively termed ‘the island syndrome’. We present here the first, phylogenetically informed, global test of the ‘island syndrome’ hypothesis, using lizards as our model organisms.LocationWorld‐wide.MethodsWe assembled a database containing 641 lizard species, their phylogenetic relationships, geographic ranges and the following life‐history traits: female mass, clutch size, brood frequency, hatchling body mass and population density. We tested for life‐history differences between insular and mainland forms in light of the island syndrome, controlling for mass and latitude, and for phylogenetic non‐independence. We also examined the effects of population density and, in insular endemics, of island area, on lizard reproductive traits.ResultsWe found that insular endemic lizards lay smaller clutches of larger hatchlings than closely related mainland lizards of similar size, as was expected by the island syndrome. In general, however, insular endemics lay more frequently than mainland ones. Species endemic to small islands lay as frequently as mainland species. Continental and insular lizards have similar productivity rates overall. Island area had little effect on lizard reproductive traits. No trait showed association with population density.Main conclusionsIsland endemic lizards mainly follow the island syndrome. We hypothesize that large offspring are favoured on islands because of increased intra‐specific aggression and cannibalism by adults. Stable populations on islands lacking predators may likewise lead to increased intra‐specific competition, and hence select for larger hatchlings that will quickly grow to adult size. This view is supported by the fact that lizard populations are denser on islands – although population density per se was uncorrelated with any of the traits we examined.

Sexual selection as a promoter of population divergence in male phenotypic characters: a study on mainland and islet lizard populations

Sexual selection is often viewed as a promoter of population divergence, although some forms of sexual selection could rather hamper divergence. In the present study, we investigated whether sexual selection promotes divergence in sexually-selected traits. We studied population variation in sexual selection in relation to colour morph and body size in islet and mainland populations of the Skyros wall lizard (Podarcis gaigeae). Females were most likely to mate with orange-throated males with small body sizes, and male body size and coloration were therefore subject to correlational sexual selection. By contrast, male mating probabilities were not affected by any female phenotypic character. We also found variation in a female resistance trait (escape propensity), with females being more prone to escape when exposed to males from other habitats. Sexual selection could potentially affect the frequencies of throat colour morphs in this species by favouring orange-throated males of small body size, although there was no evidence of sexual selection for local mates or rare phenotypes. The results obtained in the present study thus do not support a role for sexual selection as a promoter of population divergence in this species. (c) 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106, 374389. (Less)

Effects of geographic isolation on anti-snakes responses in the wall lizard, Podarcis muralis

Alteration in anti-predatory behaviour following geographic isolation has been observed in a number of taxa. Such alteration was attributed to the effect of relaxed selection in the novel environment, reinforced by the cost of anti-predatory behaviours. We studied aspects of anti-snake behaviour in 987 adult and juvenile wall lizardsPodarcis muralisfrom two mainland areas (heavy snake predatory pressure) and two islands (low snake predatory pressure), isolated from the mainland 5000 and 7000 years ago. We conducted a scented retreat site choice experiment using the odours of five different snake species (saurophagous, piscivorous or generalist feeder). Mainland lizards avoided shelters scented by saurophagous snakes, but not those scented by non saurophagous snake species. Long isolated lizards (7000 years ago) showed no anti-predator response to any snake, suggesting a total loss of anti-predatory behaviour towards saurophagous snakes. More recently isolated lizards (5000 years ago) however showed anti-snake behaviour towards a former sympatric adder species, and a tendency to avoid the scent of a sympatric generalist feeder snake. There was no difference in the anti-snake responses between adult and juvenile wall lizards from all four sites, suggesting a limited role for experience (behavioural plasticity) in the expression of anti-snake behaviour in wall lizards.

Differences in chemical signals may explain species recognition between an island lizard, Podarcis atrata, and related mainland lizards, P. hispanica

Chemical signals can be the basis of interspecific recognition and speciation in many animals. The Columbretes Islands wall lizard, Podarcis atrata is very close genetically to the mainland Iberian wall lizard Podarcis hispanica. However, a previous study suggested that chemosensory interspecific recognition would avoid reproductive interactions and hybridization between these two species. These results suggested that chemicals used in intraspecific communication might differ in composition and/or proportions between these two species. In this paper, we used gas chromatography–mass spectrometry (GC–MS) to characterize the chemical composition of the lipophilic fraction from femoral gland secretions of male P. atrata and P. hispanica. The analysis showed that chemicals found in femoral secretions varied in composition and proportions between species and between populations. Seven steroids and two unidentified waxy esters, were exclusive of P. atrata lizards from the islands. In contrast, nine steroids and other six compounds were only found in mainland P. hispanica. There were also differences in proportions of shared compounds between species. Moreover, all these differences were higher between P. atrata and P. hispanica than between any population of P. hispanica. Chemical differences might be consequence of genetic differences, but they could also be explained by adaptation to different habitats with different climatic conditions or diet resources. Compounds that are specific of each species, or differences in the pattern of compounds, could explain species recognition. Therefore, these results of chemical composition and previous studies of chemosensory recognition reinforce the fact that the genetic differences between P. hispanica and P. atrata may result in an effective reproductive isolation between these two taxa.

Stable isotopes document mainland–island divergence in resource use without concomitant physiological changes in the lizard Liolaemus pictus

Shifts in feeding ecology are believed to promote island-mainland divergence. The lizard Liolaemus pictus has several different subspecies on Chilean islands and mainland. These subspecies inhabit contrastingly different habitats both in different islands and mainland, which suggests the potential for habitat related dietary variation. We investigated the dietary habits of L. pictus by both stomach content analyses and by nitrogen stable isotope analyses (delta(15)N), which we used as a proxy variable for trophic level. We also compared the morphology of the digestive tract and the activity of intestinal digestive enzymes of mainland and island lizards. We hypothesized differences in diet and trophic level among populations and that these differences would predict the expression of the morphological and biochemical features of the digestive tract. More specifically, we predicted shorter intestines and higher levels of peptidases in more insectivorous than in more frugivorous/herbivorous lizards. The diet of L. pictus was characterized by the consumption of a wide diversity of food types, including fruit and insects, in all populations. Stable isotopes revealed higher trophic level, and hence probably higher protein intake, in mainland than in island populations, but contrary to our prediction, they had shorter intestines and higher relative activity of intestinal peptidases than mainland lizards. Furthermore, the proportion of fruit items in the stomach content was higher in the population that exhibited the lowest tropic level. These results suggest that morphological and physiological differences among populations of L. pictus are not correlated with feeding ecology, suggesting that the lizard's first responses to the selective pressure represented by a diet shift are behavioral.

Chemosensory species recognition may reduce the frequency of hybridization between native and introduced lizards

The introduction of alien species to islands by human activity can cause catastrophic consequences for small populations of island endemics. Hybridization between the endangered and endemic insular lizard Podarcis atrata (Boscá, 1916) from the Columbretes Islands (Mediterranean, Spain) and the common mainland lizard Podarcis hispanica (Steindachner, 1870) could potentially occur because mainland haplotypes have already been detected in the islands, the two species are closely genetically related, and the frequency of visitors to these islands is increasing. However, reproductive decisions of lizards are often mediated by species recognition mechanisms based on chemical cues. On the basis of this observation, even if some mainland P. hispanica lizards were introduced to the islands, interspecific recognition might make rare an eventual hybridization with the insular P. atrata. We examined interspecific chemical recognition between the insular P. atrata and the mainland P. hispanica. Our results showed that lizards of both sexes responded more strongly (i.e., directed a significantly higher number of tongue flicks) to scents of conspecific individuals than to scents of heterospecifics. Chemical recognition of conspecifics by endemic island P. atrata lizards may reduce the occurrence of hybridization with introduced mainland P. hispanica lizards and protect the insular gene pool.

Mainland versus island differences in behaviour of Podarcis lizards confronted with dangerous prey: the scorpion Buthus occitanus

Rapid divergence in behaviour of populations invading novel habitats is often considered adaptive as it may allow a species to exploit novel resources. Here we explore the behavioural response of two closely related species of Podarcis lizards living in different habitats, the Spanish mainland and a dry volcanic island, towards a potentially dangerous prey. Our results show that whereas insular lizards attacked scorpions and consequently considered them to be potential prey, mainland lizards tended to flee or ignored them. Sexual differences in the response to scorpions were pronounced in the insular habitat. Males tended to attack scorpions while females tended to ignore them. Inter‐specific and inter‐sexual differences in the responses of lizards may be mediated by body size differences between populations and sexes. The rapid changes in behaviour allowing insular lizards to recognize scorpions as potential prey may have allowed these animals to capitalize on an abundant food resource in a depauperate environment.

Individual and population energetics of a lizard on a Mediterranean islet.

Population density in the lacertid lizardPodarcis lilfordi on the Mediterranean islet of Nitge, Menorca, Balearic Islands, was found to be 12 190 ind · ha-1 (SE, ±2135), exceeding densities reported for other island or mainland lizard populations. Field metabolic rates inP. lilfordi were measured by the doubly labeled water method, allowing estimation of a population metabolizable energy demand of 13.86 MJ · ha-1 · day-1-only 9.8% of that for a theoretical mammal population of the same body mass and density. Energy demand was considerably higher than that estimated for other lizard populations, primarily due to high population density but also because of high individual daily energy expenditure (1255 KJ · day-1; body mass=5.13 g). Field metabolic rates were partitioned into maintenance and activity components by respirometry of captive animals at field body temperatures. Activity metabolism formed the main component (77.4%) of total respiratory metabolism resulting from a combination of long daily activity periods (ca. 12 h), and greatly elevated metabolism during activity (5.7 times greater than resting levels). It is hypothesized that low food availability per individual constrains the time-energy budget of this species, obligating long periods of intense foraging.

Mortality Rates of Insular Anolis Lizards: A Systematic Effect of Island Area?

Previous articleNext article No AccessNotes and CommentsMortality Rates of Insular Anolis Lizards: A Systematic Effect of Island Area?S. Joseph Wright, Robert Kimsey, and Claudia J. CampbellS. Joseph Wright Search for more articles by this author , Robert Kimsey Search for more articles by this author , and Claudia J. Campbell Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The American Naturalist Volume 123, Number 1Jan., 1984 Published for The American Society of Naturalists Article DOIhttps://doi.org/10.1086/284192 Views: 7Total views on this site Citations: 7Citations are reported from Crossref Copyright 1983 The University of ChicagoPDF download Crossref reports the following articles citing this article:Yuval Itescu, Rachel Schwarz, Shai Meiri, Panayiotis Pafilis, Sonya Clegg Intraspecific competition, not predation, drives lizard tail loss on islands, Journal of Animal Ecology 86, no.11 (Oct 2016): 66–74.https://doi.org/10.1111/1365-2656.12591Héctor Hugo Siliceo-Cantero, Andrés García Differences in growth rate, body condition, habitat use and food availability between island and mainland lizard populations of Anolis nebulosus in Jalisco, Mexico, Journal of Tropical Ecology 30, no.55 (Jun 2014): 493–501.https://doi.org/10.1017/S0266467414000297Gabriel Pinto, D. Luke Mahler, Luke J Harmon, Jonathan B Losos Testing the island effect in adaptive radiation: rates and patterns of morphological diversification in Caribbean and mainland Anolis lizards, Proceedings of the Royal Society B: Biological Sciences 275, no.16521652 (Aug 2008): 2749–2757.https://doi.org/10.1098/rspb.2008.0686Lauren B. Buckley, Joan Roughgarden A hump-shaped density-area relationship for island lizards, Oikos 113, no.22 (Feb 2006): 243–250.https://doi.org/10.1111/j.2006.0030-1299.14401.xRobert B. Kimsey Host association and the capacity of sand flies as vectors of lizard malaria in Panama, International Journal for Parasitology 22, no.55 (Aug 1992): 657–664.https://doi.org/10.1016/0020-7519(92)90015-DRobin M. Andrews Demographic correlates of variable egg survival for a tropical lizard, Oecologia 76, no.33 (Aug 1988): 376–382.https://doi.org/10.1007/BF00377032 J. A. Stamps , and M. Buechner The Territorial Defense Hypothesis and the Ecology of Insular Vertebrates, The Quarterly Review of Biology 60, no.22 (Oct 2015): 155–181.https://doi.org/10.1086/414314

The Ecological Correlates of Survival in Some Bahamian Anolis Lizards

This paper reports on the relationship of survival to size, sex, age and habitat in four species of Bahamian Anolis lizards. Lizards on a small island having relatively few bird species survived better than those on larger islands with many; survivorship in the former area is more similar to that among temperate mainland lizards than among tropical mainland lizards. Survival on two islands with different numbers of lizard species but similar numbers of bird species was similar. In A. sagrei, survival was greater in forested than the less protected open habitats. In A. sagrei but no other species, males survived less well than females; A. sagrei is the most extreme territorial polygynous species of the four. In a univariate analysis, little relation of survival to size was found in any species. Survivorship curves are extremely straight on a semilog scale, indicating constant age-specific mortality. However, a multivariate analysis for A. sagrei, using different data than for the survivorship curves and considering size rather than age, suggested a 3-way interaction between size, habitat and island. In fact, on the island with the fewest bird species, but on no other, large individuals of both sexes survived better. The significance of this result for Selander's hypothesis concerning selection for sexual size dimorphism is evaluated.

Comparison of Lipid Cycles of Holbrookia propinqua from Padre Island and Mainland Texas

We previously showed that mean clutch size of Holbrookia propinqua from the Texas mainland was significantly larger than that of lizards from Padre Island (* = 4.7 mainland, * = 3.2 island) and we provided indirect evidence that mainland females lay an average of four clutches each year while island females produce three clutches. Despite their greater egg production, main- land females are smaller than island females. Thus, we studied H. propinqua from Padre Island and mainland Texas to assess the correlation of their differing reproductive potentials and body size with patterns of lipid deposition and utilization. The patterns of lipid deposition and utilization were similar in island and mainland populations. There was a significant positive correlation between lipid weight and SVL in juveniles. Juveniles used stored lipid for winter maintenance and/or growth in early spring. The quantity of lipid stored was generally similar in island and mainland counterparts, but adult females had signifi- cantly more fat than adult males of the same population due to the presence of yolk lipids. We suggest that the major difference in the two populations is not in the quantity of lipid stored prior to reproduction, but in the proportion of the total energy budget that is devoted to reproduction. Mainland lizards are probably smaller in size than island lizards because food availability is less and because a larger share of ingested energy is devoted to reproduction and associated activities rather than to somatic growth.