Abstract
Spintharus is a genus of spiders that contained only two species until 2018 when it was demonstrated that a ‘widespread’ species was instead composed of multiple short-range endemics. This note redescribes Spintharus gracilis Keyserling and describes a new species of Spintharus (Araneae, Theridiidae), S. levergersp. nov., both based on specimens from Brazil. We also examine specimens from several additional localities in Brazil displaying variation consistent with patterns previously found within the Caribbean: geographically isolated and unique localities may contain independent species lineages. Given the limited number of specimens, profuse variation, and lack of DNA data from museum specimens, it is challenging to gauge the number of species in the observed material. Instead of describing these as new species here, we highlight this variation and hypothesize that in South America, a greater diversity of the genus across the geographical landscape will be found than predicted based on Levi’s “widespread Spintharus flavidus” hypothesis. Our results suggest that continental efforts to sample the genus would be profitable, as this charismatic group likely harbors unappreciated diversity throughout the continent.
Highlights
American cobweb spiders (Theridiidae) were revised by Herbert Levi in numerous taxonomical treatises throughout the 1950s and 1960s (e.g. Levi 1954, 1955, 1959, 1963a, b)
We find clear morphological differences between some of the specimens found at different locations, suggesting that the pattern found throughout the Caribbean of diverse, potentially speciose groups remaining undescribed will likely hold on the South American continent as well
The varying morphology of specimens found in Brazil alone suggests there remain a number of additional species to be found in the New World
Summary
American cobweb spiders (Theridiidae) were revised by Herbert Levi in numerous taxonomical treatises throughout the 1950s and 1960s (e.g. Levi 1954, 1955, 1959, 1963a, b). Many of the genera, including Spintharus, were subsequently placed in morphological (Agnarsson 2004) and molecular phylogenetic analyses (Arnedo et al 2004, Liu et al 2016), largely supporting Levi’s work. In his deliberate and practical treatment of all American araneids, tetragnathids, and theridiids Levi addressed the genus Spintharus in two papers (Levi 1954, 1963a). We redescribe S. gracilis, and describe a new species in order to call attention to likely overlooked diversity and the need for extensive sampling of fresh DNA grade material of the genus across South and Central America
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