The systematics of Pedicularis bracteosa: Morphometrics, development, pollination ecology, and molecular phylogenetics

To evaluate the evolution of floral form among Pedicularis bracteosa , an integrated analysis of morphological, developmental, pollination ecology, and DNA sequence data was performed. Morphometric analysis supported traditional taxonomic circumscription of six of eight varieties, discriminated largely by floral characters (unbeaked vs. beaked galea, short vs. long floral throat, short vs. long calyx tips) associated with pollination or herbivory. Development of beaked galeas proceeds from a meristem that is added to late stages of ontogeny. One population of P. bracteosa var. siifolia/canbyi, a beaked variety, was pollinated almost exclusively by sternotribic bumblebees. A second population was pollinated by nototribic and sternotribic bumblebees. This population set significantly fewer seeds, which can be attributed to less efficient pollen transfer by nototribic pollinators on beaked flowers. Because unbeaked varieties are pollinated by nototribic and sternotribic bumblebees, double-function pollination may be an intermediate stage of evolution that gives rise to beaked flowers. Phylogenetic analysis of DNA sequence data produced a consensus tree that (1) agrees with the taxonomy and morphometric analysis of the complex, (2) demonstrates that varieties with beaked flowers are derived from varieties with unbeaked flowers as predicted by the double-function hypothesis, and (3) is congruent with geographic and Pleistocene glacial events supporting two refugia, one in Alaska and one in northeast Washington. Probable routes of recolonization and diversification of P. bracteosa from these two sources then followed tracks south along Olympic, Cascade, Bitterroot, and southern Rocky Mountain ranges.