Question

In the late 1990s, the snail studied in Lively 1987, Potamopyrgus antipodarum, was reported as an invasive species in the U.S. Since then, its population has exploded in freshwater streams and lakes. Interestingly, all snails collected during its 30 years in the U.S. have been identified as asexual. Researchers hypothesize that this, along with one other characteristic of the environment, has allowed the snail to expand across the country.

1. How does asexuality permit rapid population expansion, when compared to other forms of reproduction? Briefly explain (1-3 sentences).

Answer 1

1. Asexuality increases homogenization at the population level. Asexuallity increases the divergence between gene copies. Therefore, the population is large and that it has had a constant size for a long time as compared to other forms of reproduction (sexual reproduction increases variability not the number). Also, invasive nature if a species avoids the growth of other species except itself. Thus, in the presence of an invasive species with asexual mode of reproduction, the snail population has expanded across the country.