In what should be our final belated post about talks at the Evolution meetings in Ottawa last month, I’d like to share some results from Bryan Falk from Susan Perkins’s Lab American Museum of Natural History. Bryan has been investigating the diversity of anole malaria parasites (Plasmodium). Like many other species of vertebrates, anoles have their own strains of malaria (not the same as the ones that effect us humans), and these lizard malaria have been the focus of numerous fascinating research projects over the years (see Schall 1996 for a review).
Bryan’s work investigated phylogenetic relationships among West Indian strains of lizard malaria using sequence data from mitochondrial DNA plus six nuclear loci. He found that Plasmodium samples on most islands form monophyletic groups, although some clades are found in both Florida and Cuba, suggesting travel between these two regions. Bryan also reported very low overall genetic diversity, the presence of most genetic variation among (rather than within) populations, and no evidence for purifying selection. Bryan’s previous work used tree-based delimitation to diagnose previously unrecognized or ambiguous taxa of Plasmodium on Hispaniola, and his new work uses a similar approach across a broader geographic scale. In the new study, species tree analyses tend to recover island-specific clades and identify 11 potentially unrecognized species within Plasmodium floridense (see Perkins 2000 for more on species delimitation in Plasmodium). Bryan’s time calibration work suggests that intra-island divergences are very young and his demographic analyses suggests that recent divergence and serial bottlenecks may be responsible for low diversity with in populations but high divergence among populations. It seems like more exciting new results with anole malaria on are on the horizon from Bryan and his collaborators.