Panter, C. T. | Search bioRxiv

bioRxiv2023

Species abundances often conform to 'abundant-centre' patterns depending on dispersal capabilities

A shared goal within macroecology, biogeography and population ecology research is to understand biodiversity patterns and the processes driving them across spatial and taxonomic scales. A common approach to study macroecological patterns and processes involves developing and testing ecogeographical rules or hypotheses. The much-debated abundant-centre hypothesis posits that species abundances are highest in their range centres and decline towards their range edges. We perform the largest global test of the hypothesis to date, on 3,675 species, using 6,055,549 abundance observations. Using meta-analytical approaches, we summarised species-level abundance-distance correlations exploring the effects of dispersal-related species traits on abundance-distance relationships. Overall, animals did not follow abundant-centre patterns, whereas plants tended to. Larger-bodied mammals were more likely to conform to abundant-centre patterns, as were mammals and freshwater fishes from higher latitudes. Perennial life cycles and large range sizes were significant predictors of abundant-centre patterns in plants. Trees and shrubs with larger seeds showed more support for abundant-centre patterns. Accounting for species dispersal improves models of abundant-centre patterns across geographic space. Assuming abundant-centre patterns represent optimal equilibria within nature, our findings suggest that abundant-centre relationships are not a general ecological phenomenon but tend to manifest only in species with higher dispersal capabilities.

ecology↗

bioRxiv2022

Causes, temporal trends and the effects of urbanisation on admissions of wild raptors to rehabilitation centres in England and Wales

Data from wildlife rehabilitation centres can provide on-the-ground records of causes of raptor morbidity and mortality, allowing threat patterns to be explored throughout time and space. We provide an overview of native raptor admissions to four wildlife rehabilitation centres (WRCs) in England and Wales, quantifying the main causes of morbidity and mortality, trends over time and whether certain causes were more common in more urbanised areas between 2001-2019. Throughout the study period 14 raptor species were admitted totalling 3305 admission records. The Common Buzzard (Buteo buteo; 31%) and Tawny Owl (Strix aluco; 29%) were most numerous. Relative to the proportion of breeding individuals in Britain & Ireland, Peregrine Falcons (Falco peregrinus), Little Owls (Athene noctua) and Western Barn Owls (Tyto alba) were over-represented in the admissions data by 103%, 73% and 69%, respectively. Contrastingly Northern Long-eared Owls (Asio otus), Western Marsh Harriers (Circus aeruginosus) and Merlin (Falco columbarius) were under-represented by 187%, 163% and 126%, respectively. Across all species, vehicle collisions were the most frequent anthropogenic admission cause (22%) and orphaned young birds (10%) were most frequent natural admission cause. Mortality rate was highest for infection/parasite admissions (90%), whereas orphaned birds experienced lowest mortality rates (16%). For one WRC, there was a notable decline in admissions over the study period. Red Kite (Milvus milvus) admissions increased over time, whereas Common Buzzard and Common Kestrel admissions declined. There were significant declines in the relative proportion of persecution and metabolic admissions, and an increase in orphaned young birds. Urban areas were positively associated with persecution, building collisions and unknown trauma admissions, whereas vehicle collisions were associated with more rural areas. Many threats persist for raptors in England and Wales, however, have not changed substantially over the past two decades. Threats associated with urban areas, such as building collisions, may increase over time in line with human population growth and subsequent urban expansion.

ecology↗