Globalization and increasing human impact on natural aquatic systems have facilitated the movement of species and the establishment of nonindigenous species enhancing hybridisation opportunities between naturally allopatric species. In this review, we focus on a special case of natural hybrid speciation and the consequences of recent anthropogenic hybridisation in the water frog complex (Pelophylax esculentus complex)
The inconsistent distribution of large-scale infection mediated die-offs and the subsequent population declines of several animal species, urges us to understand how, when, and why species are affected by disease. It is often unclear when or under what conditions a pathogen constitutes a threat to a host. Often, variation of environmental conditions plays a role. Globally Batrachochytrium dendrobatidis (Bd) causes amphibian declines; however, host responses are inconsistent and this fungus appears equally capable of reaching a state of endemism and subsequent co-existence with native amphibian assemblages. We sought to identify environmental and temporal factors that facilitate host-pathogen coexistence in northern Europe. To do this, we used molecular diagnostics to examine archived and wild amphibians for infection and general linear mixed models to explore relationships between environmental variables and prevalence of infection in 5 well-sampled amphibian species. We first detected infection in archived animals collected in 1999, and infection was ubiquitous, but rare, throughout the study period (2008-2010). Prevalence of infection exhibited significant annual fluctuations. Despite extremely rare cases of lethal chytridiomycosis in A. obstetricans, Bd prevalence was uncorrelated with this species' population growth. Our results suggest context dependent and species-specific host susceptibility. Thus, we believe recent endemism of Bd coincides with environmentally driven Bd prevalence fluctuations that preclude the build-up of Bd infection beyond the critical threshold for large-scale mortality and host population crashes.
ABSTRACT:Road-killed common toads (Bufo bufo; n51,740) from Flanders, Belgium, were tested for ranavirus and Batrachochytrium dendrobatidis (Bd) using polymerase chain reaction. Both infections were present at a very low prevalence (,0.2% with a confidence interval of 95% for ranavirus and 0.63% for Bd).
An analysis of scutellation in populations of Cerastes vipera (Linnaeus, 1758): scale characters co-vary with environmental temperature. Afr. 1. Herpetol. 45(2): 59-67. Scutellation in populations ofCerastes vipera varies geographically. Specimens occurring in more southern and wanner regions are characterized by a higher number of ventraIs, preventrals and lateral head scales. Some morphological characters (e.g. subcaudals and interoculars) are not correlated geographically with temperature profiles. Correlation of scale characters with temperature does not exclude a genetical basis. A possible genetic divergence between populations of the great sand dunes west of Chaanba-Tademait-lloggar (with a high number of ventraIs) and their northeastern Saharo-Mediterranean conspecifics (with a low number ofventraIs) is postulated, but must be confinned with supplementary genotypic methods.
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