Curvilinear interspecific density–range size relationship in small mammals in Finland
Correspondence: Atte Komonen, Department of Biological and Environmental Science, PO Box 35, FI-40014, University of Jyväskylä, Jyväskylä, Finland.
Macroecological patterns have mainly been depicted as atemporal, with existing research covering only short time periods. One fundamental pattern in macroecology is the interspecific relationship between local abundance and regional range size, which is generally considered to be positively linear. Here, we examine structural details of the relationship between abundance and range size in cyclic populations of small mammals and its long-term temporal variation.
We analysed 39 years of trapping data of Rodentia and Soricomorpha collected in field and forest habitats across Finland. Abundance was measured as the mean population density of individuals, and range size as the number of grid cells occupied and sample occupancy. Data were analysed using linear mixed models.
The relationship between mean local density and sample occupancy was generally linear, whereas the relationship between density and the number of grid cells occupied was generally curvilinear (U-shaped) for both habitats, being negative for species with small range sizes and positive for species with larger ranges. The curvilinearity was temporally consistent in both habitats.
The interspecific relationship between abundance and range size varies depending on how range size is measured. Interestingly, the curvilinear relationship between density and range size was found in an assemblage in which many of the species have fluctuating (cyclic) populations. Future research on abundance–range size relationships should focus on long-term temporal variation to better understand the underlying mechanisms and to develop macroecological theory.