Search

Aim Examining the biogeography of body size is crucial for understanding how animal communities are assembled and maintained. In tetrapods, body size varies predictably with temperature, moisture, productivity seasonality and topographical complexity. Although millennial-scale human pressures are known to have led to the extinction of primarily large-bodied tetrapods, human pressure history is often ignored in studies of body size that focus on extant species. Here, we analyse 11,377 tetrapod species of the Western Hemisphere to test whether millennial-scale human pressures have left an imprint on contemporary body mass distributions throughout the tetrapod clade. Location Western Hemisphere. Time period Contemporary. Major taxa studied Tetrapods (birds, mammals, amphibians and reptiles). Methods We mapped the distribution of assemblage-level median tetrapod body mass at a resolution of 110 km across the Western Hemisphere. We then generated multivariate models of median body mass as a function of temperature, moisture, productivity seasonality and topographical complexity, as well as two variables capturing the history of human population density and human-induced land conversion over the past 12,000 years. We controlled for both spatial and phylogenetic autocorrelation effects on body mass-environment relationships. Results Human pressures explain a small but significant portion of geographical variation in median body mass that cannot be explained by ecological constraints alone. Overall, the median body mass of tetrapod assemblages is lower than expected in areas with a longer history of high human population density and land conversion, but there are important differences among tetrapod classes. Main conclusions At this broad scale, the effect of human pressure history on tetrapod body mass is low relative to that of ecology. However, ignoring spatial variation in the history of human pressure is likely to lead to bias in studies of the present-day functional composition of tetrapod assemblages, at least in areas that have long been influenced by humans. [ABSTRACT FROM AUTHOR]

Aim The general pattern of higher species richness in tropical areas has been long recognized but the underlying cause is still debated. Two major hypotheses have emerged in recent years. The Rate Hypothesis attributes this pattern to a high rate of diversification, whereas the Time Hypothesis attributes it to greater lineage age. Here, we revisited these two hypotheses with global data sets of amphibians, birds and mammals. Location Global. Methods To test these hypotheses we evaluated the relationship between crown age and species richness, and between diversification rate and species richness within biogeographical regions. We also compared diversification rates of tropical and temperate clades, and assessed the usefulness of two phylometrics, evolutionary distinctiveness ( ED) and evolutionary rate ( ER), as proxies of age and diversification rate. Finally, we used those phylometrics in a grid cell approach to explore the spatial distribution of clade age and diversification rate. Results We found species richness of these tetrapods is best described by time (age of lineages) and that diversification rates are not significantly different between tropical and temperate areas. In addition to time, we found that historical biogeography, in some cases, has an influence on species richness patterns. In turn, this suggests that the latitudinal diversity gradient is a result of the gradient in climatic stability, with younger assemblages (hence, fewer species) occupying higher latitudes. Main conclusion Our results indicate that time, and not rate of diversification, best describes species richness patterns of amphibians, birds and mammals, and that this pattern is a 'climate effect' ultimately deriving from the latitudinal gradient in climatic stability. [ABSTRACT FROM AUTHOR]

Aim We investigated the biogeographical history of Australian blindsnakes ( Ramphotyphlops) with reference to Australia's palaeoclimatic history over the past 20 Myr, particularly the development of an extensive arid zone over this period. Terrestrial vertebrate lineages dating back to the Miocene or earlier are predicted to display some or all of the following patterns: (1) for taxa including mesic, arid and monsoonal representatives, a mesic distribution should be phylogenetically ancestral; (2) mesic and monsoon tropical lineages should have diverged before the onset of aridification (with arid lineages appearing later); and (3) refuges may have allowed local persistence and diversification of lineages in the monsoon tropical and mesic zones since the mid-Miocene. Location Continental Australia. Methods We compiled a molecular data set comprising one mitochondrial and three nuclear genes for 107 individuals belonging to 28 blindsnake species. Phylogenetic relationships were reconstructed using maximum likelihood and Bayesian inference with RA x ML and MrBayes, respectively. Divergence times were assessed using multidivtime. Ancestral habitat states (arid and non arid) were reconstructed using the maximum likelihood method implemented in Mesquite. Results The age of the Australian Ramphotyphlops radiation was estimated at 21.9 Ma (95% credibility interval: 30.2-15.1 Ma). Mesic and monsoon tropical lineages are older than the onset of aridification, with mesic distribution appearing as ancestral on phylogenies. After the onset of aridification, lineages persisted and diversified in mesic, tropical and/or rocky refugia. Arid lineages diversified more recently (< 5 Ma). Main conclusions Australian blindsnakes join several other Australian squamate lineages with tropical-mesic origins that successfully adapted to the expansion of aridity since the mid-Miocene ( c. 17 Ma) and now show evidence of multiple relatively recent evolutionary radiations across Australia. We further demonstrate that localized refugia permitted persistence and diversification of mesic taxa, with arid lineages diversifying much later (< 5 Ma) when the arid zone was well established. [ABSTRACT FROM AUTHOR]

Marin, J., Crouau-Roy, B., Hemptinne, J.-L., Lecompte, E. & Magro, A. (2010). Coccinella septempunctata (Coleoptera, Coccinellidae): a species complex? - Zoologica Scripta, 39, 591-602. Coccinella septempunctata L., the seven spot ladybird is widely distributed across the Paleartic region. Based on a few morphological characteristics and geographical origin, some populations are recognized as distinct species, e.g., the North African Coccinella algerica Kovář and Japanese Coccinella brucki Mulsant later considered to be a subspecies - C. septempunctata brucki. The objective of this study is to discuss the taxonomic status of the seven spot ladybird, in particular whether it is a complex of species or the same species throughout the Paleartic region. The relationship between populations was clarified by using a combination of molecular and limited morphometric data and assessing potential reproductive barriers by means of cross breeding. Although there is considerable variation in the size of the spots on the elytra, the results of this study confirm that all studied populations belong to the same species. [ABSTRACT FROM AUTHOR]