Quantifying the ecological niche overlap between two interacting invasive species: the zebra mussel (Dreissena polymorpha) and the quagga mussel (Dreissena rostriformis bugensis)

The zebra mussel (Dreissena polymorpha) and quagga mussel (Dreissena rostriformis bugensis) are two closely related invasive species. They usually occupy different habitats (e.g. shallow versus deep water) at a local scale, while occurring in the same broad regions at a large scale. The present study assesses the extent to which the habitat partitioning observed at local scales extends to niche partitioning at the global scale. Species distribution models (SDMs, using MaxEnt) were used to model the potential distributions of both species based on a set of environmental and dispersal related predictors. According to environmental SDMs calibrated with bioclimatic, geographic and geological factors, only 75% of the predicted quagga mussel distribution overlaps with the distribution of zebra mussel, demonstrating that the niches of the two species are moderately different at a global scale. Quagga mussels were found to occur at higher average temperature and lower average precipitation, leading to the prediction that their niche includes Mediterranean and arid regions such as California and southern Spain, two areas currently unaffected by zebra mussel. A second set of SDMs illustrated a notable influence of dispersal-related factors (e.g. human population density, closeness to commercial ports and reservoirs), on quagga mussel distribution. These models suggest that the distribution of quagga mussel is more constrained by dispersal-related factors than is the distribution of zebra mussel. Evidence suggests that economic and environmental impacts can differ between the two species; joint accurate predictions may therefore prove important for targeting precautionary management plans at the right species. Copyright (c) 2013 John Wiley & Sons, Ltd.