Hydrological connectivity drives the propagule pressure of Limnoperna fortunei (Dunker, 1857) in a tropical river–floodplain system

Abstract

River–floodplain systems are characterized by high connectivity, which favours the spread of non-native species. In floodplain, floods increase connectivity, which increases the similarity of abiotic conditions among environments. High connectivity and low environmental variability may favour the establishment of non-native species such as Limnoperna fortunei, but this has not yet been tested. We sampled L. fortunei larvae in nine connected lakes and nine isolated lakes to rivers in the upper Parana River floodplain to evaluate how spatial (connection) and abiotic (environmental variability) factors affect the larvae density of L. fortunei. We considered the rivers as propagule source of L. fortunei because this invasive species has successfully established in rivers, but not in lakes. Our findings revealed that connected lakes had a high larval density of L. fortunei, while isolated lakes had a low density. Isolated lakes presented a high multi-environmental variability, which was strong negatively related with the larval density of L. fortunei. However, the connectivity decreased the multi-environmental variability, indirectly increasing the larval density of L. fortunei. Our study illustrates that permanent connectivity with invaded environments increase the larvae density of L. fortunei in non-invaded environments, which occurs both directly (through propagule dispersion) and indirectly (by decreasing multi-environmental variability).