Burying beetles (Coleoptera: Silphidae) of the Apostle Islands, Wisconsin: Species diversity, population density and body size

Abstract

Over 2400 burying beetles, representing six species (Nicrophorus defodiens, N. sayi, N. orbicollis, N. tomentosus, N. vespilloides, and N. pustulatus), were trapped from 27 June to 4 August, 1996 at nine study sites (3 small islands, 3 large islands, and 3 mainland locations) centered around the Apostle Islands National Lakeshore in northern Wisconsin. Species diversity was greatest on the mainland and least on the smallest islands (< 600 ha). Nicrophorus defodiens, the smallest of the six species, was marginally over-represented on the smallest islands. We hypothesize that this occurred because N. defodiens can maintain a larger population for a given resource base than its larger congeners. Estimates of population density for N. defodiens were made on the two smallest islands (Raspberry and Devils) and ranged from 16-24/ha. On the small and isolated Devils Island, N. defodiens had significantly greater pronotal width compared to conspecifics at each of the other eight sites. We hypothesize that the larger body size at this site which is dominated by N. defodiens may be selected because of the greater frequency of intraspecific encounters.