No abstract

Apple snails (Ampullariidae: Pomacea) native to the New World have become agricultural and environmental pests widely in southern and eastern Asia since their introduction in about 1980. Although their impacts have been extensively documented, considerable confusion persists regarding their identities and geographical origins. Efforts to resolve the confusion have suffered from inadequate taxonomic and geographical sampling from both native and introduced ranges. Using phylogenetic and genealogical methods, we analysed 610–655 bp of cytochrome c oxidase subunit I DNA sequences from 783 apple snails from 164 Asian locations and 57 native South American locations. In Asia, we found four species of Pomacea in two clades: (1) Pomacea canaliculata and P. insularum, and (2) P. scalaris and P. diffusa. Parsimony networks and mismatch distributions indicate that the non‐native ranges of the two most widespread species, P. canaliculata and P. insularum, probably result from multiple introductions. Molecular analyses are consistent with early accounts; non‐native P. canaliculata populations trace back to multiple locations in Argentina and have probably been introduced more than once. In contrast, P. insularum was probably introduced from Brazil and Argentina independently. Multiple introductions may, in part, explain the success and rapid spread of these two species. Unlike P. canaliculata and P. insularum, P. scalaris and P. diffusa were probably introduced through the aquarium trade, derived originally from Argentina and Brazil, respectively. Possible physiological, ecological, and native range differences among these four species highlight the importance of accurate identification in understanding invasion patterns and processes, which is vital in developing and implementing management strategies.

This chapter reviews the taxonomy; habitat; morphology; mating, oviposition and fecundity; population dynamics and abundance; feeding behaviour; respiration; aestivation; temperature and salt tolerance; dispersal; distribution across South East Asia and other countries as a food item, aquarium animal and as a biological control agent of gastropods and weeds; importance as an agricultural pest of rice and other crops and as a vector of human pathogens; and chemical, biological (mainly predators) and cultural control of apple snails (Pomacea spp.).

Vicariance biogeography emerged several decades ago from the fusion of cladistics and plate tectonics, and quickly came to dominate historical biogeography. The field has since been largely constrained by the notion that only processes of vicariance and not dispersal offer testable patterns and refutable hypotheses, dispersal being a random process essentially adding only noise to a vicariant system. A consequence of this thinking seems to have been a focus on the biogeography of continents and continental islands, considering the biogeography of oceanic islands less worthy of scientific attention because, being dependent on stochastic dispersal, it was uninteresting. However, the importance of dispersal is increasingly being recognized, and here we stress its fundamental role in the generation of biodiversity on oceanic islands that have been created in situ, never connected to larger land masses. Historical dispersal patterns resulting in modern distributions, once considered unknowable, are now being revealed in many plant and animal taxa, in large part through the analysis of polymorphic molecular markers. We emphasize the profound evolutionary insights that oceanic island biodiversity has provided, and the fact that, although small in area, oceanic islands harbour disproportionately high biodiversity and numbers of endemic taxa. We further stress the importance of continuing research on mechanisms generating oceanic island biodiversity, especially detection of general, non‐random patterns of dispersal, and hence the need to acknowledge oceanic dispersal as significant and worthy of research.