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Description
The genus Pimus Chamberlin 1947 is a group of small-bodied, cribellate, ground-dwelling spiders found throughout central and northern California, and into central Oregon. Ten species of Pimus have been formally described. Historically, descriptions of Pimus species have been based on female morphology alone, and in some cases based on single female specimens. The goals of this study are to re-evaluate these species hypotheses using molecular data (CO1, actin and 28S), and use new collections as well as museum specimens to provide a more comprehensive examination of both female and male morphology. No hypotheses regarding species relationships in the genus have ever been presented, so this study also presents the first species-level phylogenetic hypotheses for the genus. Pimus species are distributed throughout many biogeographic regions in California, and seem to be characterized by small, allopatric distributions - this study also explores the biogeographic history and timing of diversification in Pimus. Phylogenetic analyses recover twelve distinctive genetic clades, six of which correspond to previously-defined morphological species. Biogeographic regions do not include monophyletic groups of species, with sister relationships most often occurring between geographically disjunct sister species. Many biogeographic relationships seen in Pimus are mirrored in other taxa (spiders, salamanders), and include relationships that span the Central Valley, and concordant breaks in the Klamath/Trinity mountains, Sierra Nevadas and Coast Ranges. Neither male nor female genitalia were particularly useful in species delimitation, however the shape of the male palpal RTA (retrolateral tibial apophysis) does correspond phylogenetically to deeper groupings of species.
