Effects of capability for dispersal on the evolution of diversity in Antarctic benthos

The likelihood of marine invertebrates to maintain large geographic ranges is widely dependent on the ability of their early ontogenetic stages to disperse over long distances. Marine benthic invertebrates inhabiting the cold-stenothermal environment of the Southern Ocean are known for their overall reduced number of pelagic larvae, or drifting stages of any kind, when compared with organisms elsewhere in the sea. The diversity of organisms thriving in Antarctic waters is the result of evolution in situ and of the intrusion of species from surrounding seas. The reasons for a high level of endemism and a stunning diversity of benthic invertebrates found today are frequently discussed in the literature, but the mechanisms whereby diversity has been controlled over time remain largely theoretical. Here, I suggest that, indeed, early life-history patterns play a key role in defining the radiation and the speciation potential of Antarctic benthic invertebrates. In arguing this case, I synthesize the growing body of molecular studies on population connectivity in Antarctic benthic invertebrates, and compare this information with knowledge of their life histories and biogeography. I conclude that differences in early life-history patterns are key to the resilience potential of species in response to late Cenozoic glacial periods and propose that there is a direct relationship between rate of speciation and the ability of taxa to disperse.