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The Life Aquatic with Spiders (Araneae): Repeated Evolution of Aquatic Habitat Association in Dictynidae and Allied Taxa

Crews, Sarah1; Garcia, Erika2; Spagna, Joe3; Van Dam, Matthew1; Esposito, Lauren1

Published Nov 05, 2019 on Dryad. https://doi.org/10.5061/dryad.qrfj6q5b2

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Abstract

Despite the terrestriality of spiders, species across a diverse array of families are associated with aquatic habitats. Many species in the spider family Dictynidae are associated with water, either living near it, or in the case of Argyroneta aquatica (Clerck, 1757), in it. Previous studies have indicated that this association arose once within the family. Here we test the hypothesis of a single origin via the broadest phylogeny of dictynids and related “marronoids” to date using several taxa that were not previously sampled in molecular analyses to provide the first quantitative test of the hypothesis put forth by Wheeler et al. (2016). We sampled 281 terminal taxa from 14 families, assembling a matrix with 4380 total basepairs of data from most taxa. We also assembled an atlas of morphological traits with potential significance for both ecology and taxonomy. Our resulting trees indicate that an aquatic habitat association has arisen multiple times within dictynids. Dictynidae and the genus Dictyna Sundevall, 1833 are polyphyletic, and the genera Lathys Simon 1884 and Cicurina Menge, 1871 remain unplaced. A review of aquatic habitat associations in spiders indicates that it occurs in members of at least 21 families. With our morphological atlas, we explore characters that have been implicated in aiding an aquatic lifestyle which in the past may have caused confusion regarding taxon placement. Our results indicate that not all spiders with traits thought to be useful for aquatic habitat associations occupy such habitats, and that some spider taxa lacking these traits are nonetheless associated with water.