The role of abiotic factors in intertidal selection: A comparison between an invader and its sibling species

The mechanisms that determine species distribution patterns are a central theme in ecological research. Interest in this area has intensified as biologists attempt to predict (1) the effects of global climate change on species' range limits and (2) patterns of invasion by non-native species. Conservation biologists have further urged researchers to look for simple ecological rules when studying organisms that can be applied broadly to conservation efforts (e.g. reserve design). However, quantifying the environmental factors driving an organism's ecological niche remains problematic and research has emphasized a need to understand better how abiotic factors change in space and time. Marine rocky intertidal ecosystems are extremely physiological stressful environments and often considered a model system to study species distribution patterns. The main objective of this dissertation is to examine how abiotic stresses affect selection in intertidal habitats. Specifically, I have focused on the Mytilus edulis complex (the common blue marine mussel), which contains a worldwide invasive species (M. galloprovincialis) and several non-invading congeners (M. trossulus and M. edulis ). Chapter 1 explores the implications of movement behavior on mussel dislodgement in a Mytilus spp. hybrid zone. Results suggest that M. edulis has faster moving rates to the exterior of mussel beds than M. galloprovincialis and thus experiences increased dislodgement due to wave forces. In chapter 2, I investigate how spatial variability in habitat temperature may drive patterns of selection between M. galloprovincialis (invasive) and M. trossulus (native). This work showed higher abundance of M. galloprovincialis in habitats with more extremes in low tide intertidal body temperatures (i.e. exposed intertidal). Chapter 3 expands on the findings in chapter 3 by exploring how both water temperature and aerial exposure affects M. galloprovincialis and M. trossulus in a controlled laboratory experiment. Survival and growth of M. galloprovincialis was higher in all conditions tested compared to M. trossulus. In the final chapter of my dissertation I review the literature of M. galloprovincialis to explore the attributes of this successful invasive species. A literature review suggests that several factors that likely play a strong role in the invasive ability of M. galloprovincialis compared to co-occurring mussels.