Doonan, J., Beatty, G.E., Sigwart, J.D. and Provan, J. 2012. Extensive local-scale gene flow and long-term population stability in the intertidal mollusk Katharina tunicata (Mollusca: Polyplacophora). Biological Journal of the Linnean Society 106: 589-597.
The authors write that "Katharina tunicata, commonly known as the Black Katy Chiton, is an abundant intertidal grazer with a limited pelagic larval stage of approximately six days (Paine, 1992)," which is distributed along the Pacific coast of North America from Alaska's Aleutian Islands to southern California, where they say that it is "an important regulator of intertidal ecosystems." Nevertheless, they indicate that the species "has recently suffered declines in localized parts of its range as a result of exploitation by humans and sea otters." And noting that it is also "under threat from the effects of climate change," they sought to determine "whether local-scale barriers to gene flow could potentially compromise the dispersal capacity of the species in the face of climate change."
What was done
Doonan et al. - as they briefly describe their work - "used nuclear single-nucleotide polymorphisms and mitochrondrial DNA sequencing to elucidate fine-scale patterns of genetic variation between populations of the Black Katy Chiton separated by 15-150 km in southwest Vancouver Island."
What was learned
The four UK researchers from Queen's University in Belfast report that "both the nuclear and mitochondrial data sets revealed no genetic differentiation between the populations studied," as well as the fact that "an isolation-with-migration analysis indicated extensive local-scale gene flow, suggesting an absence of barriers to dispersal." In addition, they say that "population demographic analysis also revealed long-term population stability through previous periods of climate change associated with the Pleistocene glaciations," and - more particularly - at the Pleistocene-Holocene transition of approximately ten thousand years ago, as discussed by Fields et al. (1993).
What it means
The conclusions of Doonan et al. are that "taken together, the current evidence of high dispersal and a lack of biogeographic barriers to gene flow, coupled with the signature of long-term population stability through previous periods of climate change, suggest that this dispersal potential may act as a lifeline for K. tunicata as their southerly habitats rapidly warm, and a poleward migration is required for survival," additionally citing the work of Graham et al. (2010) in this regard. Now, if we could just keep those pesky humans (and sea otters) in check!!!
Fields, P.A., Graham, J.B., Rosenblatt, R.H. and Somero, G.N. 1993. Effects of expected global climate change on marine faunas. Trends in Ecology and Evolution 8: 361-367.
Graham, C.H., VanDerWal, J., Philips, S.J., Moritz, C. and Williams, S.E. 2010. Dynamic refugia and species persistence: tracking spatial shifts in habitat through time. Ecography 33: 1062-1069.
Paine, R.T. 1992. Food-web analysis through field measurement of per capita interaction strength. Nature 355: 73-75.Reviewed 28 November 2012