Phylogenetic studies of the laurels and heathers (Ericaceae: Ericoideae, Phyllodoceae, and Cassiope clades)

The current study explores phylogenetic studies within the laurel and heather clades within the Ericaceae. The two groups are members of two closely related clades, the Ericoideae and Cassiope. Phylogenetic relationships within the subfamily Ericoideae were investigated first in order to establish its main clades. Five main clades were recovered. The first four are the tribes Ericeae (African and European heathers), Empetreae (crowberries and Diplarche, a Rhododendron-like species), Rhodoreae (Rhododendron and relatives) and Bryantheae, comprised of two poorly understood genera, Bryanthus and Ledothamnus. The fifth (Phyllodoceae) includes plants such as the mountain laurels (Kalmia), the mountain heathers (Phyllodoce) and their close relatives.;The Phyllodoceae was the subject of the second part of the research. The goal here was to establish a species-level phylogeny and to examine historical biogeography of the tribe. DIVA analysis was used to infer ancestral areas of nodes, and putative vicariance events. Identification of these events was followed by relative dating of vicariance events using BEAST (Bayesian Evolutionary Analysis by Sampling Trees). This analysis revealed vicariance events in the Northern Hemisphere that likely occurred in the same general span of time. A date was hypothesized for these vicariance events, and a second BEAST analysis used these dates as calibration points to permit absolute dating of remaining nodes. These analyses revealed a likely Tertiary history of the Phyllodoceae, with distributions in North America impacted by cooling and aridification during the Eocene and Miocene, and later by glacial cycles in the Pliocene and Pleistocene.;The moss heathers (Cassiope) were the focus of the third project. This genus has been associated with virtually all major clades within the Ericaceae. Most recently, it was determined using molecular characters that Cassiope is sister to the Ericoideae. The bell heathers (Harrimanella) had been thought to be closely related to Cassiope, because its flowers and general habit are similar. Based upon anatomical characters, however, Harrimanella was thought to be more closely related to the blueberries (subfamily Vaccinioideae) or the Australian epacrids (subfamily Styphelioideae). In addition to estimating a species-level phylogeny for the genus Cassiope, the phylogenetic position of Harrimanella within the Ericaceae was also investigated. It was determined that Harrimanella is properly excluded from Cassiope, in agreement with anatomical data. Within Cassiope, morphological characters are generally homoplasious. Phylogenetic trends are evident in some anatomical characters, including vessel density and stem diameter. These results indicate that morphology in Cassiope is evolutionarily labile, and that anatomical characters may be tuned to local ecology.