Relative contributions of fixed and dynamic heterogeneity to variation in lifetime reproductive success in kestrels (Falco tinnunculus)

Many species show large variation in lifetime reproductive success (LRS), with a few individuals producing the majority of offspring. This variation can be explained by factors related to individuals (fixed heterogeneity) and stochastic differences in survival and reproduction (dynamic heterogeneity). In this study, we study the relative effects of these processes on the LRS of a Dutch Kestrel population, using three different methods. First, we extended neutral simulations by simulating LRS distributions of populations consisting of groups with increasingly different population parameters. Decomposition of total LRS variance into contributions from fixed and dynamic heterogeneity revealed that the proportion of fixed heterogeneity is probably lower than 10% of the total variance. Secondly, we used sensitivities of the mean and variance in LRS to each parameter to analytically show that it is impossible to get equal contributions of fixed and dynamic heterogeneity when only one parameter differs between groups. Finally, we computed the LRS probability distribution to show that even when all individuals have identical survival and reproduction rates, the variance in LRS is large (females: 27.52, males: 12.99). Although each method has its limitations, they all lead to the conclusion that the majority of the variation in kestrel LRS is caused by dynamic heterogeneity. This large effect of dynamic heterogeneity on LRS is similar to results for other species and contributes to the evidence that in most species the majority of individual variation in LRS is due to dynamic heterogeneity.     

A Vegetation, Climate and Environment Reconstruction Based on Palynological Analyses of High Arctic Tundra Peat Cores (5000–6000 years BP) from Svalbard

As a reference for ongoing studies reconstructing past vegetation, climate and environment, pollen spectra in tundra peat profiles from Svalbard, were investigated. The base of tundra peat cores collected from Ny Ålesund, Stuphallet, Blomstrand and Isdammen has been ¹⁴C dated to 350–490 BP, 5710 BP, 4670 BP and 700–900 BP, respectively. The Stuphallet and Blomstrand (Brøggerhalvøya) peat profiles were composed of a peat developed in a nutrient enriched and wet tundra environment of steep birdcliffs. Pollen concentrations were low, Brassicaceae pollen dominated the whole profile. In contrast, the Ny Ålesund and Isdammen profiles contained high pollen concentrations and suggest a nutrient-poor, dry tundra environment. Pollen of the polar willow, Salix polaris, occurred commonly throughout all four peat profiles. In the relatively high resolution (10 years per peat core sample) analysis of the Ny Ålesund core, starting before or at the beginning of the Little Ice Age (LIA, 16th-mid 19th century), dominance of Saxifraga oppositifolia indicates a cold and dry climate, followed by a decline of Saxifraga oppositifolia and gradual increase of Salix polaris after the LIA, which indicates a moist and milder climate.     

Under-exploration of Three-Dimensional Images Leads to Search Errors for Small Salient Targets

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Sociality, density-dependence and microclimates determine the persistence of populations suffering from a novel fungal disease, white-nose syndrome

Disease has caused striking declines in wildlife and threatens numerous species with extinction. Theory suggests that the ecology and density-dependence of transmission dynamics can determine the probability of disease-caused extinction, but few empirical studies have simultaneously examined multiple factors influencing disease impact. We show, in hibernating bats infected with Geomyces destructans, that impacts of disease on solitary species were lower in smaller populations, whereas in socially gregarious species declines were equally severe in populations spanning four orders of magnitude. However, as these gregarious species declined, we observed decreases in social group size that reduced the likelihood of extinction. In addition, disease impacts in these species increased with humidity and temperature such that the coldest and driest roosts provided initial refuge from disease. These results expand our theoretical framework and provide an empirical basis for determining which host species are likely to be driven extinct while management action is still possible.