Effects of environmental factors on the distribution of the exotic species Mytilopsis sallei (Récluz, 1849) (Bivalvia: Dreissenidae) on the Northeast coast of Brazil.
The invasive bivalve Mytilopsis sallei caused several economic and ecological impacts in Asia. In Brazil, M. sallei was first reported in 2004, and thus far, little is known about its ecological impact on Brazilian estuaries. The present study aims to evaluate the abundance and distribution of M. sallei and to analyse the environmental factors that led to the establishment of this species in a Brazilian Northeast estuary. Sampling was carried out in six stations along the estuary, covering a broad spectrum of salinities. Results showed that M. sallei was the most abundant benthic species in this estuary, although it was not broadly distributed, occurring only in one station (S1), the most polluted and the one with the lowest salinities (mean 17.3 ± 11.56), which was the abiotic factor controlling the distribution of M. sallei. This station also had the lowest diversity of species (H' = 0.3269). The main M. sallei microhabitat was the pneumatophores roots from mangrove trees and decomposing wood. Despite the high abundance of M. sallei in S1, this species experienced negative effect of other benthic species suggesting that its distribution was limited by the high abundance of native species in other stations. Our results suggest that the distribution of M. sallei is influenced by a set of characteristics: preference for low salinity, favourable substrate type, tolerance to pollutants, and less direct competitors. Understanding how invasive species are distributed and relate to native species will provide more robust strategies to help maintain environmental health that ultimately will prevent the expansion of M. sallei population.