Systematics of the Californian euctenizine spider genus Apomastus (Araneae : Mygalomorphae : Cyrtaucheniidae): the relationship between molecular and morphological taxonomy

Abstract

The genus Apomastus Bond & Opell is a relatively small group of mygalomorph spiders with a limited geographic distribution. Restricted to the Los Angeles Basin, San Juan Mountains, and San Joaquin Hills, Apomastus occupies a fragile habitat rapidly succumbing to urban encroachment. Although originally described as monotypic, the genus was hypothesised to contain at least one additional species. However, females of the two reputed species are morphologically indistinguishable and the authors were unable confidently to assign specific status to populations for which they lacked male specimens. Using an approach that combines geographic, morphological and molecular data, all known populations are assigned to one of two hypothesised species. Mitochondrial DNA cytochrome c oxidase I sequences are used to infer population phylogeny, providing the evolutionary framework necessary to resolve population and species identity issues. Conflicts between the parsimony and Bayesian analyses raise questions about species delineation, species paraphyly, and the application of molecular taxonomy to these taxa. Issues relevant to the conservation of Apomastus species are discussed in light of the substantive intraspecific species divergence observed in the mtDNA data. The type species, Apomastus schlingeri Bond & Opell, is redescribed and a second species, Apomastus kristenae, sp. nov., is described.