Biodiversity and reduced extinction risks in spatially isolated rodent populations

Ecologists have rarely explored the potential influence of local (alpha) bi odiversity on the stability and local extinction of spatially isolated popu lations. Twenty years of annual counts of a small, grazing rodent (Utah pra irie dogs, Cynomys parvidens) from 20 different isolated local populations (colonies) in southern Utah, U.S.A. were analysed. These prairie dogs exhib ited large fluctuations and repeated extinctions at individual colonies dur ing the census period. Frequency of extinction at a colony declined dramati cally as the number of locally occurring plant species increased. This patt ern was not explained by differences among colonies in plant productivity, plant species composition, colony size, or variability in annual counts. Th us, lower extinction risk of consumer populations may be associated with gr eater resource diversity, and maintaining high local plant diversity may he lp sustain spatially isolated herbivore populations in fragmented habitats.