Ascoglossan (=Sacoglossa) Molluscs in the Florida Keys: Rare Marine Invertebrates at Special Risk
Abstract:The Florida Keys archipelago supports a diverse fauna of ascoglossan molluscs (33 species, including three Florida Keys endemics). Populations of approximately half of these are declining from a variety of known and unknown causes, including habitat destruction, siltation, eutrophication, and overcollection. Western Atlantic ascoglossans exhibit a range of characteristics that increase extinction risk. About half of Florida Keys ascoglossans have nonplanktotrophic development, which may limit dispersal and recolonization. Some species with planktotrophic development also have poor dispersal ability. About two-thirds of Florida Keys slugs live in habitats that are naturally fragmented; species often occur at low density and in small populations. Despite small population size and low biomass density, ascoglossans' niche (feeding on ecologically dominant primary producers) suggests ecological importance. Conservation of ascoglossan biodiversity may require protection of remaining optimal habitats, which are concentrated in near shore communities. Recent degradation of Florida Bay by seagrass dieoff may further restrict suitable habitats by mobilization of silt, which appears to inhibit ascoglossan populations. Ascoglossans may serve as accessible models for other rare marine invertebrates. Extrapolation to other rare taxa suggests possible importance of rare marine invertebrates as regulators of ecologically patent taxa, particularly if trophic specialists. Other rare invertebrates may also have an unrecognized high incidence of nonplanktotrophic development, or of non-dispersing planktotrophic larvae, predisposing to extinction by anthropogenic effects, an important consideration in biodiversity management.
Document Type: Research Article
Publication date: 1994-05-01
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