Taxonomic revision of the opilionid genus Acuclavella shear, 1986 (Opiliones, Ischyropsalidoidea) based on molecular phylogenetics and morphometrics with description of four new species

The genus Acuclavella was described from the Western Hemlock Zone of the Pacific Northwest by Shear in 1986. His description of four new species from northern Idaho was based in large part on very small sample sizes: Acuclavella cosmetoides, the type species, was described from a single male and female; A. shoshone was described from two males and one female; and A. quattuor was described from a single female. Each of these three species was known only from their northern Idaho type locality. The fourth species, A. merickeli, was represented by thirteen individuals; twelve of these, four males and eight females, were from the type locality in northern Idaho. The remaining individual, collected 350 miles west of the type locality in the Cascade Mountains of western Washington State, was considered by Shear to be conspecific to A. merickeli due to morphological similarities. In this study, focused sampling effort in northern Idaho and western Washington has increased the number of localities and number of individuals known for the genus by more than an order of magnitude. Unique morphologies encountered represent both new species and variation within species not seen by Shear due to inadequate sample sizes. An integrative taxonomic approach used to test species hypotheses results in the discovery of four new species; two from western Washington (A. leonardi and A. Olympics) and two from northern Idaho (A. sheari and A. cf. quattuor). An integration of morphologies and ambiguous placement in molecular phylogenetics rejects species-level distinction between two species of Acuclavella, and A. shoshone is here synonymized with A. cosmetoides. This research has resulted in discovery and description of male A. quattuor. Due to the few animals used by Shear (1986) in his descriptions, and the results of phylogenetic and morphometric analyses, a revision of the genus Acuclavella is warranted.