Summary: Effects of range size on speciesarea relationships
Andrew P. Allen* and Ethan P. White
Department of Biology, University of New Mexico, 167 Castetter Hall,
Albuquerque NM 87131-1091, USA
It has been known for some time that the slope of the speciesarea relationship increases
asymptotically at broad spatial scales when richness is plotted against area on logarithmic axes.
At continental to global scales, speciesarea relationships are determined to a large extent by
the abundance and size distribution of species ranges. Here we present an analytical model that
explicitly quantifies the effects of range size on speciesarea relationships. The model shows
how range size and plot area interact to control the form of speciesarea relationships at broad
spatial scales. It also demonstrates how changes in spatial scale affect biodiversity patterns by
changing the relative influence of range size and range abundance on species richness. Our
model provides an explanation for the broad-scale upturn of the speciesarea relationship, but
more work is needed to incorporate the effects of range size, habitat heterogeneity, individual
sampling and other variables into a unified framework that can account for speciesarea
relationships at all scales.
Keywords: biodiversity, macroecology, power law, range size, spatial scale, speciesarea
relationship, species richness.