Exhaustive sampling in a Southern Hemisphere global biodiversity hotspot: inventorying species richness and assessing endemicity of the little known jarrah forest spiders

Abstract

Spiders from Southern Hemisphere temperate ecosystems may contribute substantially to global biodiversity in terms of species richness and distinctiveness of the biota. To date, few studies have considered their potential contribution in this context and most have restricted focus to a limited number of families. Here richness, endemicity and the proportion of described taxa at specific, generic and familial ranks are examined from a global biodiversity hotspot. Spiders were sampled from a region of Jarrah Eucalyptus marginata Forest (approx. 20 000 hal in southwestern Australia (32°16'S, 116°06'E). Two hundred and eighty-seven species (from 138 described genera, and 46 families) were collected. Using the ACE, ICE and Cha02 estimators, the inventory was considered 93 to 95% complete. Continued sampling, however, would be costly as the effort to add one additional species had become high in terms of the number of specimens collected per additional species. Taxonomic knowledge of the fauna was limited for most groups. Only 83 species (29%) could be assigned a name. Of the remaining unnameable species, >95 could not be assigned to described genera. Six could not be assigned to a family. Where possible, analyses showed high levels of endemicity at generic and species levels; 64% of described genera were known only from Gondwanan land-masses, 41% were endemic to Australia. Most described species were known only from Australia (77%). Of these, >36% had only been collected within Western Australia (most were known only from the South-West Botanical Province). However, these results are constrained as few countries have as limited knowledge of their spider fauna as Australia.