| Abstrakt: |
Non-indigenous species may drive declines in global freshwater biodiversity. Japanese mystery snails, Heterogen japonica (previously Cipangopaludina / Bellamya / Viviparus japonica), have invaded numerous freshwater systems in North America. To resolve questions about its population demography and genetics, we surveyed ponds and rivers from six Mid-Atlantic USA locations (Richmond, Virginia to Washington, D.C.) in 2018 and 2019 for mystery snails and co-occurring indigenous snails. A random subset of each snail species (max N = 80) per location was assessed for population demographics (size, sex), and brooding embryos were counted in mystery snails. Because morphological identification can be difficult to discern from its congener, the Chinese mystery snail (Cipangopaludina chinensis), we used a mitochondrial barcoding gene (COI) to confirm identity of H. japonica and also serve as a population genetics marker. Our barcoding confirmed that the mystery snails detected in our surveys were H. japonica, and that, compared to the indigenous range, its populations have low genetic diversity and limited genetic structure. Even so, H. japonica had the highest overall catch-per-unit-effort among all snails and sites. In demographic analyses, H. japonica populations skewed towards females, and females brooding live young were the largest across all sites. The number of live young ranged from 14 to 101/female (average: 52 live young/female). Further, a linear relationship existed between brooding female shell length and the number of live young for all sites, except one. Possible explanations could include site-level differences in abiotic or biotic parameters, but this requires further research. Altogether, the snail's reproductive capacity documented here suggests that H. japonica has the potential to undergo additional population growth, especially if large females spread to new locations. Moreover, it highlights another example of an invasive species with high population abundance, demographic performance, and distributional range even with depauperate genetic diversity. [ABSTRACT FROM AUTHOR] |
