Assessing environmental factors structuring populations and movement dynamics of the invasive snail Tarebia granifera in a subtropical Austral reservoir

Abstract

Invasive alien species continue to spread and proliferate in waterways worldwide, but environmental drivers of invasion dynamics lack assessment. Understanding alien species ability to self-disperse via locomotion following arrival to new environments is also critical for prediction of invasion success. The study assessed: (i) the distribution and abundance of Tarebia granifera and the potential drivers of population structure in Nandoni reservoir; and (ii) compared movement traits between two widespread invasive alien snails, T. granifera and Physa acuta, to assess their net distance and velocity and determine dispersal potential. Tarebia granifera was widespread at sites invaded, with abundances exceeding 500 individuals m-2 at impacted areas. Tarebia granifera was significantly associated with sediment (i.e., chlorophyll-a, Mn, sediment organic carbon (SOC) and organic matter (SOM)) and water (i.e., pH, conductivity, total dissolved solids (TDS)) variables. Tarebia granifera seemed to exhibit two recruitment peaks in November and March, identified via size-based stock assessment. Tarebia granifera displayed a significantly greater velocity and covered a significantly larger net distance than Physa acuta. The exploratory behaviour (i.e., mean, or absolute turning angles and straightness index) did not differ significantly between the two alien species; both species showed a slight tendency to turn counter clockwise. Overall, the study shows that there was higher snail abundance during the summer season, furthermore, sediment and water variables were found to be important in structuring T. granifera populations. The present study suggests a more rapid capacity to self-disperse in T. granifera than P. acuta, but a similar level of exploratory behaviour between the two species. The study provided autecological information and insights on the distribution and extent of spread of T. granifera, given the often-overlooked role of animal behaviour in promoting invasion, this information can help inform and predict the invasion pattern of invasive alien freshwater snail. This information can also help in the development of invasive alien snail management action plans within the region and elsewhere.