Population genetic structure of invasive apple snails Pomacea maculata in Louisiana

Aquatic invasive species decrease biodiversity and disrupt economic systems worldwide. Apple snails (Ampullaridae) from the genus Pomacea are globally invasive species that are highly damaging to aquaculture and aquatic ecosystems. Pomacea maculata was introduced to Louisiana in the early 2000s and rapidly spread throughout the southern half of the state, where invasive populations now threaten valuable aquaculture economies and a large area of aquatic ecosystems that sustain biodiversity important to commercial and recreational fisheries. Despite these risks, little work has been dedicated to understanding how apple snails disperse through invaded areas in Louisiana. To shed light on potential dispersal dynamics, we assessed population genetic structure of P. maculata in Louisiana at multiple spatial scales using microsatellites of snails collected from seven sampling locations. Overall, genetic diversity was relatively high across all sampling locations. Significant genetic structure was observed among sampling sites, indicating Barataria Preserve and the four sampling locations within Terrebonne Basin as distinct populations. Genetic distances were smallest among the four sampling locations within Terrebonne Basin. These findings suggest that dispersal within hydrologic units is higher than between units, meaning that apple snails may primarily move through systems through passive downstream dispersal. However, geographically distant populations also showed evidence of genetic mixing, pointing toward human-aided long-distance dispersal events. Regular dispersal of apple snails within and among hydrologic units highlights the risk of invasions in highly interconnected aquatic systems where dispersal rates may be especially high due to human modifications.