ABSTRACT. Critical analysis of existing spider species lists for Wisconsin, Michigan, Ohio, Indiana and Illinois reveals 900 species recorded from the five-state region (284 genera, 40 families). All non-native, Palearctic, or otherwise questionable species records were scrutinized, and their status is discussed. The most speciose families in the region are the Linyphiidae (almost 24% of species), Salticidae (10.3%), Theridiidae (8.9%), Lycosidae (8.8%), and Araneidae (7.7%). All sources used for spider species names and species records are unambiguously quoted. Spider species records are presented in tables allowing comparison of family composition among the states, and prediction of number of heretofore unrecorded species. Richness among states is analyzed and found to be dependent on varying degrees of sampling effort. As a new tool, a Spider Species Name Concordance Table allows tracking previously published spider species names to the currently valid name of every species record. The study demonstrates the need for crucial pieces of scientific infrastructure, such as complete species catalogs, and the great utility of faunistic and taxonomic data to meet today's biodiversity challenges.
Keywords: Midwest spider fauna, checklist, faunistics, Araneae, gap analysis, Illinois, Indiana, Ohio, Wisconsin, Michigan
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In the past, faunal studies and alpha-taxonomic work played a significant role in biological research. Their importance and influence in biological science diminished during the past 6 decades (Wheeler 2004), especially in the developed (and supposedly well-studied) regions in the world, such as Europe and North America. The recent focus on biodiversity decline and conservation efforts demonstrates significant gaps in our faunistic knowledge. While species discovery for vertebrates is well advanced, the discovery of the majority of non-vertebrate species on the planet (Agenda 2000) lags far behind (Knapp et al. 2005). A 139% increase of recorded bivalve species from the Florida Keys between 1995 and 2004 illustrates the point (Bieler & Mikkelsen 2004).
Conservation efforts focus mainly on the estimated species-richness of habitats and the occurrence of endangered and threatened species (Mace 2004). Charismatic vertebrate species and their protection are most often invoked in conservation actions, whereas the majority of animal biodiversity, the invertebrates, remains on the sideline. We often know so little about species' ranges and abundance that species-richness estimates for any particular habitat or region are vague and uncertain.
Spiders, a mega-diverse group with 38,000 described species (Platnick 2005) are a case in point. As insect predators, they play a pivotal role in the regulation of insect populations in all terrestrial habitats. Species lists offer solid baseline data for large-scale biogeographic analyses, survey and monitoring efforts, and tracking of environmental changes. These lists form the foundation of species-richness estimates. Yet, reliable, up-to-date spider species lists for the 50 United States are not available, because faunistic research declined (and lost funding) before the job was done (Crawford 1988). Consequently, the current assemblage of spider species lists suffers from several problems, impeding biogeographic research as well as hampering their utility for ecological research and conservation efforts.
Spider species lists for various states and habitats were completed over a long period of time....