Diversity of litter-dwelling beetles in the Ouachita Highlands of Arkansas, USA (Insecta: Coleoptera)

A survey of forest litter-inhabiting Coleoptera was conducted in deciduous forests of the Ouachita Mountains in western Arkansas during 1991-1992. A total of 102 Berlese samples were collected, weighed, and processed during the 12-month study. From 741 kg of sifted forest litter, we counted and sorted 10 663 adult beetles representing 46 families and 400 species. The family Staphylinidae was taxonomically and numerically dominant, comprising 46% of species and 63% of individuals. Problems in assessing species richness of forest litter Coleoptera faunas result from a lack of taxonomic revisions, occurrence of sex-limited diagnostic characters, and inadequate information about larval-adult species associations and life histories. A randomized species accumulation curve indicated that species addition ranged from 14 species per sample during the first ten samples to 1.5 species per sample during the final ten. Richness estimates generated from the empirical data ranged from 434 species (Michaelis-Menten and Coleman richness estimators) to 590 species (second order jacknife). The area sampled is biogeographically significant because it harbors numerous habitat-restricted species that are endemic to the Ouachita Mountains or the Interior Highland region, as well as disjunct populations of species that are also found in the southern Appalachian Mountains. Deciduous forest habitats of the Ouachita Mountains, particularly beech-maple riparian forest, should be given special consideration in forest conservation planning because of their significance as refugia for these and other endemic and disjunct arthropods.