Genetic Differentiation and Crypsis Among Members of the Myco-heterotrophic Pyrola picta Species Complex (Pyroleae: Monotropoideae: Ericaceae)

The Pyrola picta species complex (Pyroleae: Monotropoideae: Ericaceae) is thought to be composed of three morphological taxa within a single species, Pyrola picta. All taxa typically inhabit mature coniferous or Fagaceous forests of North America west of the Rocky Mountains from British Columbia to Baja California, Mexico between ca. 250 and 3,000 m in elevation. Taxa within P. picta are distinguished from each other on the basis of leaf morphology and the degree to which they employ mycoheterotrophy rather than photosynthesis, but considerable variation has been documented in both of these features, confounding diagnosis. For this study Pyrola picta, P. picta f. aphylla, and P. picta ssp. dentata were collected from populations throughout their range in western North America and examined for genetic differences to determine whether they indeed constitute a single polymorphic species or, alternatively, multiple distinct species. Multiple individuals per population were described morphologically and then examined genetically using both amplified fragment length polymorphisms (AFLP) and nucleotide polymorphisms of the nuclear ITS region. Phylogenetic analyses of ITS nucleotide sequence polymorphism using the parsimony criterion in addition to maximum likelihood and Bayesian models provide concordant estimates for the monophyly of multiple taxa within P. picta, suggesting that members of this species complex may actually represent multiple, reproductively isolated species. Statistical analyses of AFLP support the hypothesis that members of the P. picta complex are genetically distinct taxa that exhibit considerable phenotypic overlap and low levels of interspecific genetic admixture. With caveats, we propose that the current taxonomic description of members within the P. picta species complex be reevaluated given the evidence for genetic distinction among its members.