Abstract
We report the discovery of a second western Atlantic brackish-coastal cochliopid gastropod in San Francisco Bay [Spurwinkia salsa (Pilsbry, 1905)], and detail the first records for a widely distributed member of the family, Tryonia porrecta (Mighels, 1845), from artificial lakes (in the Phoenix metropolitan area). These identifications were based on morphological criteria and supported by mitochondrial DNA sequence data that also indicates little or no divergence of the newly reported populations, which is consistent with evolutionarily recent spread or separation. Spurwinkia salsa was most likely introduced to San Francisco Bay either in recent decades in bait worm packing or ships’ ballast or in the 19 h or early 20 h century in solid ballast or with oyster imports. The discovery of T. porrecta in artificial lakes in the Phoenix area in 1984 and 2014 may be due to either recent arrival in the area or to dispersal into a newly available habitat from a population long present in the area. In either case, the occurrence of T. porrecta in the Phoenix area is likely due to transport on birds along an eastern branch of the Pacific Flyway. The discovery of T. porrecta in artificial lakes suggests that this species (which is typically distributed in thermal springs) is more broadly tolerant than previously thought. Additional spread of this unusual snail within the highly modified aquatic ecosystem of the Phoenix metropolitan area (which includes more than 900 artificial lakes) would appear likely.
Highlights
The Cochliopidae is a large (>250 species), predominantly New World family of caenogastropods that occurs in a wide variety of brackish-coastal and inland aquatic habitats (Hershler and Thompson 1992)
Long (Spurwinkia salsa (Pilsbry, 1905); Mazurkiewicz 1972) duration. This constrains the dispersal of inland species and renders them especially vulnerable to anthropogenic stressors on aquatic ecosystems: for example, 31 of the 45 inland cochliopid species in the United States currently are listed as endangered by the American Fisheries Society (Johnson et al 2013)
The San Francisco Bay population was considered cryptogenic because the native range of T. porrecta has not been well established and because the primarily parthenogenetic mode of reproduction of this species may facilitate a pattern of natural dispersal that cannot be distinguished from anthropogenic spread
Summary
The Cochliopidae (formerly a Hydrobiidae subfamily; Wilke et al 2001, 2013) is a large (>250 species), predominantly New World family of caenogastropods that occurs in a wide variety of brackish-coastal and inland aquatic habitats (Hershler and Thompson 1992). Long (Spurwinkia salsa (Pilsbry, 1905); Mazurkiewicz 1972) duration This constrains the dispersal of inland species and renders them especially vulnerable to anthropogenic stressors on aquatic ecosystems: for example, 31 of the 45 inland cochliopid species in the United States currently are listed as endangered by the American Fisheries Society (Johnson et al 2013). Littoridinops monroensis (Frauenfeld, 1863), a brackish-water cochliopid having a well-established native range along the western Atlantic and eastern Gulf Coasts, was recently reported in the San Francisco Bay estuary (Hershler et al 2007), which has a long history of species introductions (Cohen and Carlton 1998) This new population was thought to have been introduced by shipping, with snails or egg capsules possibly transported in residual ballast sediment. The San Francisco Bay population was considered cryptogenic (per Carlton 1996) because the native range of T. porrecta has not been well established and because the primarily parthenogenetic mode of reproduction of this species may facilitate a pattern of natural dispersal that cannot be distinguished from anthropogenic spread
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