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Populations of the same species occupying different microhabitats can either exhibit generalized traits across them or display intraspecific variability, adapting to each microhabitat in order to maximize performance. Intraspecific variability contributes to the generation of diversity, following selection and adaptation, and understanding such variability is important for comprehending how individuals choose their microhabitats. Compared with interspecific variability, however, intraspecific variability in functional morphology and its relationship with microhabitat preference and use have been relatively little studied. Here we examined whether populations of the gecko Mediodactylus kotschyi that differ in the substrates they occupy display habitat-specific behaviors and differing morphologies associated with functional adaptation to their microhabitats. We collected 207 geckos from under or on rocks or on trees from seven populations in Greece. On large islands individuals occupy both substrates; whereas small islets are devoid of trees and the geckos are restricted to rocks, while on the mainland they are only found on trees. We determined gecko substrate preferences in the laboratory, together with their clinging abilities to the different substrates. We measured their limbs, digits, and claws and assessed how these measurements relate to clinging ability. Geckos from all populations preferred the tree made available to them, but this preference was not statistically significant. Geckos from both large and small islands clung better to the tree than to the rock in the laboratory, while those from the mainland clung similarly to both substrates. Geckos collected from trees had longer manual digits and hind limbs. Geckos collected from large and small islands had taller (longer on the dorso-ventral axis; henceforth "deeper") claws. Longer digits and deeper but shorter claws were associated with a better ability to cling to rocks. Our findings suggest that while M. kotschyi is potentially preferentially arboreal, due to the great variation and plasticity it possesses, it can successfully also exploit the habitats available on the smallest, treeless islets in the Aegean Sea. Our study suggests that the dichotomous use of generalist versus specialist in describing species' habitat use is oversimplified, and we suggest the use of a generalist–specialist gradient instead. [ABSTRACT FROM AUTHOR]

Based on a comprehensive literature survey, we determined the sources of the terrestrial vertebrate species on Christmas Island, asking where they originated relative to Wallace's Line (the southern end of the divide lies 1100 km to the east, where the Lombok Strait adjoins the eastern Indian Ocean). The two bats, Pipistrellus murrayi and Pteropus natalis , are from the west. Concerning the endemic and 'resident' bird species, one is from the west (Collocalia natalis), four are from the east (Accipiter fasciatus , Egretta novaehollandiae , Falco cenchroides and Ninox natalis) and the other 15 are ambiguous or indeterminate. Most of the land-locked species are also from the east: rodents Rattus macleari and Rattus nativitatis , and squamates Cryptoblepharus egeriae , Emoia nativitatis and Lepidodactylus listeria. Additionally, two have westerly origins (Crocidura trichura and Cyrtodactylus sadleiri), one is ambiguous (Emoia atrocostata) and another is unknown (Ramphotyphlops exocoeti). West-directed surface currents that flow across the eastern Indian Ocean towards Christmas Island would have facilitated most of the land-animal colonizations. We therefore suggest that Wallace's Line be redrawn such that the landmass is placed on the Australasian side of this fundamental biogeographical boundary. [ABSTRACT FROM AUTHOR]

Insular animals are thought to be under weak predation pressure and increased intraspecific competition compared with those on the mainland. Thus, insular populations are predicted to evolve 'slow' life histories characterized by fewer and smaller clutches of larger eggs, a pattern called the 'island syndrome'. To test this pattern, we collected data on egg volume, clutch size and laying frequency of 31 Aegean Island populations of the closely related geckos of the Mediodactylus kotschyi species complex. We tested how predation pressure, resource abundance, island area and isolation influenced reproductive traits. Isolation and predation were the main drivers of variation in life-history traits. Higher predator richness seemed to promote faster life histories, perhaps owing to predation on adults, whereas the presence of boas promoted slower life histories, perhaps owing to release from predation by rats on the eggs of geckos. Insular geckos followed only some of the predictions of the 'island syndrome'. Predation pressure seemed to be more complex than expected and drove life histories of species in two opposing directions. Our results highlight the importance of considering the identity of specific predators in ecological studies. [ABSTRACT FROM AUTHOR]

The tempo andmode of body size evolution on islands are believed to be well known. It is thought that body size evolves relatively quickly on islands toward the mammalian modal value, thus generating extreme cases of size evolution and the island rule. Here, we tested both theories in a phylogenetically explicit context, by using two different species-level mammalian phylogenetic hypotheses limited to sister clades dichotomizing into an exclusively insular and an exclusively mainland daughter nodes. Taken as a whole, mammals were found to show a largely punctuational mode of size evolution. We found that, accounting for this, and regardless of the phylogeny used, size evolution on islands is no faster than on the continents. We compared different selection regimes using a set of Ornstein-Uhlenbeck models to examine the effects of insularity of the mode of evolution. The models strongly supported clade-specific selection regimes. Under this regime, however, an evolutionary model allowing insular species to evolve differently from their mainland relatives performs worse than a model that ignores insularity as a factor. Thus, insular taxa do not experience statistically different selection from their mainland relatives. [ABSTRACT FROM AUTHOR]

Extreme morphologies of many insular taxa suggest that islands have unusual properties that influence the tempo and mode of evolution. Yet whether insularity per se promotes rapid phenotypic evolution remains largely untested. We extend a phylogenetic comparative approach to test the influence of novel environments versus insularity on rates of body size and sexual size dimorphism diversification in Anolis. Rates of body size diversification among small-island and mainland species were similar to those of anole species on the Greater Antilles. However, the Greater Antilles taxa that colonized small islands and the mainland are ecologically nonrandom: rates of body size diversification among small-island and mainland species are high compared to their large-island sister taxa. Furthermore, rates of diversification in sexual size dimorphism on small islands are high compared to all large-island and mainland lineages. We suggest that elevated diversifying selection, particularly as a result of ecological release, may drive high rates of body size diversification in both small-island and mainland novel environments. In contrast, high abundance (prevalent among small-island lizard communities) mediating intraspecific resource competition and male–male competition may explain why sexual size dimorphism diversifies faster among small-island lineages than among their mainland and large-island relatives. [ABSTRACT FROM AUTHOR]