Cryptic speciation, genetic diversity and gene flow in the California turret spider Atypoides riversi (Araneae: Antrodiaetidae)

Abstract

Populations of the turret spider Atypoides riversi from eight central Californian sites were compared based on variation at ten allozyme loci. Multidimensional scaling of interpopulation genetic distances defined four population units (Coast Range, Sierran, Valley, Jenness Camp), corroborating the distinctness of Coast Range and Sierran populations indicated by a prior study. While the species status of these units has yet to be determined, Jenness Camp is the most likely to represent a new species, given its clear genetic uniqueness (two fixed allelic differences). Populations in all units were generally in Hardy-Weinberg equilibrium with no evidence of inbreeding, though variability was minimal (mean H o = 2.8%, mean P = 15.4%). Reduced variability in these populations may be the result of repeated bottlenecks, environmental homogeneity, and/or directional selection. Interpopulation differentiation within units was significant in the absence of intervening forest habitat and was substantially less in its presence, indicating that gene flow is likely only when forest corridors exist. To foster preservation of the existing gene pool and enhance participation in it, management of the units of At. riversi should focus on maintaining as many populations in situ as possible and facilitating connections between them, while also creating or restoring habitat for potential colonization.

Prey‐race drives differentiation of biotypes in ant‐eating spiders

“…Evidence of how spiders have diversified is not abundant, but it is largely assumed that the prevailing mechanism was geographic isolation. The type of habitat and geographic barriers prevented gene flow in cryptic antrodiaetid species (Ramirez & Chi 2004); ecological differentiation together with island separation led to both radiation in tetragnathid and dysderid spiders (Gillespie 2005; Macías‐Hernández, Oromí & Arnedo 2008; Cardoso et al. 2010) and sexual selection in a salticid spider (Masta & Maddison 2002).…”

Multilocus genealogies reveal multiple cryptic species and biogeographical complexity in the California turret spider Antrodiaetus riversi (Mygalomorphae, Antrodiaetidae)

“…The following sites correspond exactly to six of the sites sampled by Ramirez & Chi (2004): Bayview, Monitor, Jenness, Sutter Buttes, Point Reyes and Monterey. In addition, Ramirez & Chi (2004) sampled at two sites in the Santa Cruz Mountains, near our Felton and Montebello sites. Sites are grouped into genetic clades, following results of phylogenetic analyses (see text and Fig.…”

Combining genetic and geospatial analyses to infer population extinction in mygalomorph spiders endemic to the Los Angeles region

“…Main, 1987;Vincent, 1993;Coyle & Icenogle, 1994). Site fidelity leads to considerable spatial clumping in appropriate microhabitats and extreme population genetic structuring (Bond et al, 2001;Ramirez & Chi, 2004). These life-history traits promote geographic fragmentation over space and time, resulting in a large number of taxa that have small geographic distributions.…”