Search

We determined the distribution of two cryptic mussel species (Mytilus edulisandM. trossulus) along full gradients of wave exposure in northwest Atlantic rocky intertidal habitats. Research was conducted in Nova Scotia (Canada) and Maine (United States) and species were determined using genetic analyses. In very sheltered habitats, onlyM. edulisoccurred. In sheltered, exposed, and very exposed habitats, both species co-existed,M. edulispredominating in Maine andM. trossulusin Nova Scotia. Hybrids were absent or rare. The distribution of mussels regardless of species (Mytilusspp.) was remarkably consistent across levels of wave exposure in both regions. In very sheltered habitats, organisms were large (4–5 cm long, on average) and old (7–8 years, on average) and occurred in low densities. In sheltered, exposed, and very exposed habitats, organisms were small (< 1 cm, on average) and young (1–2 years, on average); density was low in sheltered and very exposed habitats, but high in exposed habitats. Abundance data for predatory snails (dogwhelks,Nucella lapillus) and canopy-forming algae (Ascophyllum nodosumandFucusspp.) suggest that predation and facilitation may explain some of the observed changes in mussel population traits along the wave exposure gradients. Our results could be useful as baseline information to predict the effects of the progressive increase in wave action caused by climate change on intertidal mussel populations. [ABSTRACT FROM AUTHOR]