Discovery of introduced and cryptogenic cochliopid gastropods in the San Francisco Estuary, California

We report the first discovery in the San Francisco Estuary (‘Estuary’)of two cochliopid gastropods, Littoridinops monroensis and Tryoniaporrecta. These identifications were based on morphologicalcriteria and supported by analysis of mitochondrial DNA (cytochromec oxidase subunit I, COI) sequence data. We also report thefirst discovery of males in parthenogenetic T. porrecta. Thenew records represent large range extensions for both of theseNorth American species, which were previously recorded frompredominantly brackish habitats along the western Atlantic-GulfCoast (L. monroensis) and thermal springs in the Great Basinand lower Colorado River region (T. porrecta). The COI haplotypeobserved in Estuary specimens of L. monroensis differed fromthose detected in two western Atlantic populations by only 1–3 bp,suggesting recent divergence which is not consistent with theseparation of these two areas by imposing terrestrial barrierssince at least the Pliocene. We suggest that L. monroensis wasrecently introduced to the Estuary by transoceanic shipping,adding to the large exotic biota that has invaded this highlydisturbed ecosystem. The COI haplotype observed in Estuary specimensof T. porrecta is closely similar to haplotypes detected inNevada and Utah populations and highly divergent relative tothe single haplotype observed in other California populations.The implications of these findings for the status of T. porrectain the Estuary are unclear, because the native range of thisparthenogen has not been established and its scattered distributionin the West may be attributable to natural dispersal acrossland (on birds) and/or anthropogenic spread. Although we suggesttreating T. porrecta as cryptogenic in the Estuary, a nativestatus may be suggested by independent (subfossil) evidencethat this snail was locally present prior to establishment ofthe area as a major centre of human population and commercein the 1850s. (Received 13 April 2007; accepted 25 June 2007)