The influence of harmful plant Wedelia biflora expansion on terrestrial mollusks in xisha islands.
It is well-documented that the expansion of Wedelia biflora profoundly impacts the structure and functions of the native plant community in the Xisha Islands, but the effects of this expansion on terrestrial mollusks remain unclear. In this study, we investigated the population density and shell features (e.g. height, width and mass) of the major groups of terrestrial mollusks: Achatina fulica, Subulinidae, Camaenidae and Ariphantidae. Mollusk conditions were assessed under different degrees of W. biflora expansion on Yongxing Island. Results showed: (1) As the coverage of W. biflora increased, the population density of A. fulica and Subulinidae also increased, decreased for Camaenidae, and initially increased and then decreased for Ariphantidae. (2) Population density of A. fulica small-sized individuals increased at a disproportionately higher rate with W. biflora expansion, while the density of other body size remained unaltered. (3) W. biflora expansion inhibited certain shell features of A. fulica, which adopted an r strategy to cope with W. biflora expansion. In summary, the expansion of W. biflora on Yingxing Island altered the body sizes, population density and community structure of terrestrial mollusks. To cope with this expansion, different mollusks adopted different response strategies, a selective process which should be considered when managing the spread of invasive species.