Molecular phylogenetics of nursery web spiders (Araneae: Pisauridae)

Abstract

Pisauridae Simon, 1890, or nursery web spiders, are a large family with a worldwide distribution and very diverse life history strategies. Despite being named for their nursery webs, similar structures are built by some members of Ctenidae, Trechaleidae, and Oxyopidae. Pisauridae has no known morphological synapomorphies that circumscribe all members of the family, and delineation of subfamilies has been a longstanding issue. In addition, several recent molecular phylogenetic studies have called into question the monophyly of Pisauridae. Here, we infer a phylogeny of Pisauridae with nine genetic markers (12S, 16S, 18S, 28S, actin, COI, histone H3, ITS2, and NADH) combined with ultraconserved elements (UCEs) to test the monophyly of the group and determine intrafamilial relationships. Our study includes a total of 81 terminals (59 of them pisaurids). Our maximum likelihood and gene coalescence analyses strongly suggest that as currently circumscribed, the family Pisauridae is not monophyletic. To circumscribe Pisauridae as a monophyletic group, based on our molecular results, we propose the restoration of the family Dolomedidae Simon, 1876 (rank resurrected) to include the genera Dolomedes Latreille, 1804 and Bradystichus Simon, 1884. In addition, based on morphological evidence, we also place in Dolomedidae the genera Megadolomedes Davies & Raven, 1980; Tasmomedes Raven, 2018; Mangromedes Raven, 2018; Ornodolomedes Raven & Hebron, 2018; and Caledomedes Raven & Hebron, 2018. We provide a phylogenetic delimitation of the three subfamilies of Pisauridae: Halinae, Thaumasiinae, and Pisaurinae. Ten pisaurid genera are deemed incertae sedis in terms of their placement. In light of our hypothesized molecular phylogeny, we discuss the morphological characters and putative synapomorphies of Pisauridae and propose diagnostic characters for its subfamilies and for the family Dolomedidae, along with taxonomic notes about genera not included in our study.