Estimating global pholcid spider diversity
Less than 200 years ago, French American zoologist Nicolas Hentz estimated global spider diversity to be above 2,000 species. Current estimates (76,000-170,000) are certainly closer to reality, but the wide range of estimates also shows that we are still far from having a reliable estimate of spider diversity.
One major problem is that the large majority of (spider) material currently available in museum collections suffers from a range of problems, some of which impede reasonably good estimates: (1) few localities are well collected, while most are poorly collected; (2) few species are well represented, while most are either missing or represented by only one or a few specimens and thus often by only one sex; (3) many specimens are poorly preserved because delicate spiders like many pholcids tend to be damaged when collected together with other spiders or arthropods; (4) locality data are often imprecise; (5) basic ecological data like microhabitat are usually not avilable.
For this reason I have started several long-term projects with the aim of producing reasonable estimates of the actual pholcid diversity in several megadiverse regions: the Atlantic Forest in Brazil (ongoing project, currently funded by CNPq, Brazil), the Greater Antilles in the Caribbean, tropical Africa (previous DFG project: HU980/9-1), and Southeast Asia (current DFG project: HU980/11-1). The basic idea is simple: extrapolations from species per locality, endemism levels, and distribution patterns are combined with vegetation data to produce a first hypothesis of overall diversity based on more than just speculation.
Current data suggest that only about 20-30% of pholcid species have been described so far. The global total may be about 5,000 species (1,400 currently known).