Global bioregions of reptiles confirm the consistency of bioregionalization processes across vertebrate clades

Aim

The identification of biogeographical zones has been fundamental in broadscale biodiversity analyses over the last 150 years. If processes underlying bioregionalization, such as climatic differences, tectonics and physical barriers, are consistent across vertebrate clades, we expect that groups with more similar ecological characteristics would show more similar bioregions. Lack of data has so far hampered the delineation of global bioregions for reptiles. Therefore, we integrated comprehensive geographic distribution and phylogenetic data of lepidosaurian reptiles to delineate global reptile bioregions, compare determinants of biogeographical boundaries across terrestrial vertebrates and test whether clades showing similar responses to environmental factors also show more similar bioregions.

Location

Global.

Time Period

Present.

Major Taxa Studied

Reptiles, amphibians, birds, mammals.

Methods

For reptiles, we used phylogenetic beta diversity to quantify changes in community composition, and hierarchical clustering to identify biogeographic ‘realms’ and ‘regions’. Then, we assessed the determinants of biogeographical boundaries using spatially explicit regression models, testing the effect of climatic factors, physical barriers and tectonics. Bioregions of reptiles were compared to those of other vertebrate clades by testing the overall similarity of the spatial structure of bioregions, and the match of the position of biogeographical boundaries.

Results

For reptiles, we identified 24 evolutionarily unique regions, nested within 14 realms. Biogeographical boundaries of reptiles were related to both climatic factors and past tectonic movements. Bioregions were very consistent across vertebrate clades. Bioregions of reptiles and mammals showed the highest similarity, followed by reptiles/birds and mammals/birds while amphibian bioregions were less similar to those of the other clades.

Main Conclusions

The overall high similarity among bioregions suggests that bioregionalization was affected by similar underlying processes across terrestrial vertebrates. Nevertheless, clades with different eco-physiological characteristics respond somewhat differently to the same environmental factors, resulting in similar but not identical regionalizations across vertebrate clades.     

Interspecific Social Interactions and Breeding Success of the Frog Rana latastei: A Field Study

Interspecific reproductive interference can affect fitness‐related breeding performance, thus influencing fitness and distribution of populations. Laboratory studies demonstrated the social interference of Rana dalmatina males on R. latastei breeding females: the presence of heterospecific males reduced the percentage of viable embryos in R. latastei eggs. Here, we tested if the negative effects of R. dalmatina males on R. latastei reproductive success occur in field conditions. We compared the percentage of viable embryos of eggs laid in field conditions from populations where R. latastei breeds alone with the percentage of viable embryos of populations where R. latastei cohabits with R. dalmatina. We did not find any significant difference in percentage of viable embryos between R. latastei populations syntopic and allotopic with R. dalmatina, nor a relationship between the relative abundance of heterospecifics and reproductive success. In natural conditions, the presence of heterospecific males does not seem to interfere with the reproductive success of R. latastei. The experimental procedure may influence the interaction among individuals. Therefore, we suggest to validate on natural populations the results of experiments dealing with complex interactions.     

Human activities alter biogeographical patterns of reptiles on Mediterranean islands

Aim The theory of island biogeography predicts species richness based on geographical factors that influence the extinction–colonization balance, such as area and isolation. However, human influence is the major cause of present biotic changes, and may therefore modify biogeographical patterns by increasing extinctions and colonizations. Our aim was to evaluate the effect of human activities on the species richness of reptiles on islands. Location Islands in the Mediterranean Sea and Macaronesia. Methods Using a large data set (n = 212 islands) compiled from the literature, we built spatial regression models to compare the effect of geographical (area, isolation, topography) and human (population, airports) factors on native and alien species. We also used piecewise regression to evaluate whether human activities cause deviation of the species–area relationship from the linear (on log–log axes) pattern, and path analysis to reveal the relationships among multiple potential predictors. Results The richness of both native and alien species was best explained by models combining geographical and human factors. The richness of native species was negatively related to human influence, while that of alien species was positively related, with the overall balance being negative. In models that did not take into account human factors, the relationship between island area and species richness was not linear. Large islands hosted fewer native species than expected from a linear (on log–log axes) species–area relationship, because they were more strongly affected by human influence than were small islands. Path analysis showed that island size has a direct positive effect on reptile richness. However, area also had a positive relationship with human impact, which in turn mediated a negative effect on richness. Main conclusion Anthropogenic factors can strongly modify the biogeographical pattern of islands, probably because they are major drivers of present‐day extinctions and colonizations and can displace island biodiversity from the equilibrium points expected by theory on the basis of geographical features.     

Modelling the potential distribution of the Bridled Skink,Trachylepis vittata (Olivier, 1804), in the Middle East

The Bridled Skink, Trachylepis vittata, is widespread in the Middle East and eastern coastal Mediterranean areas and inhabits foothills throughout the arid regions of the Middle East. With the help of more than 146 distribution records from Iran, Turkey, Syria, Israel, Jordan, Cyprus, Egypt, Lebanon and Libya, we analysed the influence of climate on the distribution pattern. According to the Maximum Entropy model, the most influential factors that determined T. vittata distribution are: precipitation of coldest quarter, Normalised Difference Vegetation Index (NDVI) and precipitation in the warmest quarter. The model suggests that the western slopes of the Zagros Mountains in Iran and slopes in the southern regions of Anatolia around the Mediterranean Sea are suitable for this species. The species is associated with areas with intermediate NDVI (150-180) (a measure of primary productivity), high winter precipitation (>300?mm) and dry summer (<50mm). The association with rainy winter limits the presence of the species in lowlands. The Zagros Mountains may act as a biogeographic barrier that limits the species dispersal eastward, because of their scarce precipitation.     

Conserving adaptive genetic diversity in dynamic landscapes

Genetic variation supplies the raw material for adaptation, evolution and survival of populations and has therefore been a key focus of conservation biology ever since its foundation (Soulé 1985). In previous decades, the neutral component of genetic diversity (generated by mutation and shaped by drift) has been the subject of intense scientific research, fuelled by the increasing availability of molecular markers. On the other hand, the adaptive component of genetic diversity, which is shaped by the action of natural selection, has long remained elusive and difficult to assess, especially at small spatial or temporal scales (Ouborg et al. 2010). Fortunately, new technological and methodological developments now make it possible to identify loci in the genome that are influenced by selection, and thus to get a more complete view of genetic diversity. One article featured in this issue of Molecular Ecology is a good example of this recent breakthrough. Richter-Boix et al. (2011) examined a network of moor frog populations breeding in contrasting habitats in order to understand how landscape features influence patterns of genetic variation. They combined information from both neutral markers and loci putatively under selection to quantify the relative roles of selection and isolation in the evolution of fine-scale local adaptations in these populations. This study nicely illustrates how data on polymorphisms of neutral and adaptive loci can now be judiciously synthesized to help identify the best strategies for preserving adaptive variation, and more generally to enlighten conservation and population-management plans.