Body size is intrinsically linked to metabolic rate and life-history traits, and is a crucial determinant of food webs and community dynamics1,2. The increased temperatures associated with the urban-heat-island effect result in increased metabolic costs and are expected to drive shifts to smaller body sizes3. Urban environments are, however, also characterized by substantial habitat fragmentation4, which favours mobile species. Here, using a replicated, spatially nested sampling design across ten animal taxonomic groups, we show that urban communities generally consist of smaller species. In addition, although we show urban warming for three habitat types and associated reduced community-weighted mean body sizes for four taxa, three taxa display a shift to larger species along the urbanization gradients. Our results show that the general trend towards smaller-sized species is overruled by filtering for larger species when there is positive covariation between size and dispersal, a process that can mitigate the low connectivity of ecological resources in urban settings5. We thus demonstrate that the urban-heat-island effect and urban habitat fragmentation are associated with contrasting community-level shifts in body size that critically depend on the association between body size and dispersal. Because body size determines the structure and dynamics of ecological networks1, such shifts may affect urban ecosystem function.
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RBINS Staff Publications 2018
The volume of human carbon (δ13C) and nitrogen (δ15N) isotope data produced in archaeological research has increased markedly in recent years. However, knowledge of bone remodelling, its impact on isotope variation, and the temporal resolution of isotope data remains poorly understood. Varied remodelling rates mean different elements (e.g., femur and rib) produce different temporal signals but little research has examined intra-element variability. This study investigates human bone remodelling using osteon population density and the relationship with carbon and nitrogen isotope data at a high resolution, focusing on variation through femoral cross-sections, from periosteal to endosteal surfaces. Results demonstrate considerable differences in isotope values between cross-sectional segments of a single fragment, by up to 1.3‰ for carbon and 1.8‰ for nitrogen, illustrating the need for standardised sampling strategies. Remodelling also varies between bone sections, occurring predominantly within the endosteal portion, followed by the midcortical and periosteal. Therefore, the endosteal portion likely reflects a shorter period of life closer to the time of death, consistent with expectations. By contrast, the periosteal surface provides a longer average, though there were exceptions to this. Results revealed a weak negative correlation between osteon population density and δ15N or δ13C, confirming that remodelling has an effect on isotope values but is not the principal driver. However, a consistent elevation of δ15N and δ13C (0.5‰ average) was found between the endosteal and periosteal regions, which requires further investigation. These findings suggest that, with further research, there is potential for single bone fragments to reconstruct in-life dietary change and mobility, thus reducing destructive sampling.
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RBINS Staff Publications 2024
We analyze an important new opus on the snakes of West and Central Africa co-authored by Jean-Philippe Chippaux and Kate Jackson. We correct the identification of some of the illustrated snakes of the genera Dipsadoboa, Grayia, Limaformosa and Philothamnus. We provide more detailed localities for more than 30 photographs of snakes of the genera Atractaspis, Bitis, Boaedon, Bothrophthalmus, Causus, Dasypeltis, Dendrolycus, Eryx, Gonionotophis, Grayia, Hydraethiops, Leptotyphlops, Limaformosa, Mehelya, Myriopholis, Natriciteres, Philothamnus, Polemon, Python, Thelotornis, Tricheilostoma and Xenocalamus, from Botswana, Cameroon, Democratic Republic of the Congo, Ethiopia, Ghana, Ivory Coast, Liberia, Republic of the Congo and Tanzania. An interval of four years between the submission of the manuscript of the book and its publication explains the inaccuracy of many distribution maps, and the fact that recent taxonomic changes and numerous recently described species and genera were not included.
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RBINS Staff Publications 2020
