Abstract
Long-distance dispersal via rafting is now recognised as a key process influencing the distribution and connectivity of many marine and coastal species, especially in the Southern Ocean. Rafting scenarios are, however, often invoked in somewhat simplistic ways that inadequately account for clear differences in biogeographic outcomes. Too often, the consequences of different life histories, ecologies, and dispersal frequencies are ignored. In Southern Ocean gastropods, for example, some species show evidence of recent and ongoing connectivity due to frequent rafting among distant populations. By contrast, other gastropod taxa appear to have experienced long-distance dispersal less often, with rafting events enabling occasional colonisation of new territory but not ongoing gene flow among populations. Such differences appear to be underpinned by variations in several life-history characters, with, for instance, direct-developing taxa more suited to long-distance rafting events that might span multiple generations. Rafting success is also shaped by a diverse suite of factors including the durability of the raft, the presence/absence of resources and competitors (intra- or inter-specific) at the destination, species’ thermal and other environmental tolerances, and the frequency and intensity of extreme events such as storms. Several of these factors are being influenced by climate change, so a detailed understanding of their roles is increasingly important – particularly as many species’ distributions are shifting as a result of global warming. Here we highlight several instances Southern Ocean molluscan taxa have been subject to long-distance rafting. In all these cases, however, a full explanation of the biogeographic patterns observed requires added detail and nuance. These examples illustrate what is needed to achieve an improved and properly integrated understanding of the eco-evolutionary outcomes of long-distance dispersal via rafting.
Oral presentation.