Invasive freshwater snails are less sensitive to population density than native conspecifics.

Abstract

Species invasion can negatively affect natural ecosystems by causing biodiversity loss, changing nutrient cycling processes, and altering trophic webs. Understanding how and why some species or lineages become invasive is critically important to preventing and controlling invasions. We address whether key life history traits of invasive vs. native lineages – here Potamopyrgus antipodarum - differ in response to environmental stressors that could determine the outcome of invasions. We focus here on population density, which is a fundamental characteristic of all populations and to which native lineages of P. antipodarum are very sensitive. This New Zealand freshwater snail successfully invaded Europe in the 19th century and is a more recent invader in North America. In just a few decades, invasive populations of P. antipodarum have spread across much of North America, with detrimental effects for local food webs and native species. We quantified individual growth rate and embryo number in P. antipodarum from multiple distinct native range and invasive lineages cultured from the juvenile stage across three different population density treatments. The growth of native but not invasive lineages decreased as density increased, and reproduction in invasive but not native snails was positively affected by increased density. These results are consistent with a scenario where differential sensitivity to population density could help explain why some lineages become invasive while others do not. Our findings also align with previous studies that show that invasive lineages of P. antipodarum exhibit a relatively wide range of tolerance to environmental stressors.