  Chloroplast microsatellites are becoming increasingly popular markers for
population genetic studies in plants, but there has been little focus on their
potential for demographic inference. In this work the utility of chloroplast
microsatellites for the study of population expansions was explored. First, we
investigated the power of mismatch distribution analysis and the F(S) test with
coalescent simulations of different demographic scenarios. We then applied
these methods to empirical data obtained for the Canary Island pine (Pinus
canariensis). The results of the simulations showed that chloroplast
microsatellites are sensitive to sudden population growth. The power of the
F(S) test and accuracy of demographic parameter estimates, such as the time of
expansion, were reduced proportionally to the level of homoplasy within the
data. The analysis of Canary Island pine chloroplast microsatellite data
indicated population expansions for almost all sample localities. Demographic
expansions at the island level can be explained by the colonization of the
archipelago by the pine, while population expansions of different ages in
different localities within an island could be the result of local extinctions
and recolonization dynamics. Comparable mitochondrial DNA sequence data from a
parasite of P. canariensis, the weevil Brachyderes rugatus, supports this
scenario, suggesting a key role for volcanism in the evolution of pine forest
communities in the Canary Islands.
