Species delimitation of Cattleya coccinea and C-mantiqueirae (Orchidaceae): insights from phylogenetic and population genetics analyses

The high-altitude Southeastern Brazilian Cattleya coccinea clade includes two taxonomically challenging species, Cattleya coccinea and Cattleya mantiqueirae, the latter considered restricted to the mountain range of Serra da Mantiqueira. To hypothesize the existence of evolutionary independent lineages corresponding to these species, we inferred phylogenetic relationships and described patterns of population genetic diversity and structure of populations from six localities based on ISSR and cpDNA sequence data. Results do not support the species C. coccinea and C. mantiqueirae as previously circumscribed. Most analyses recovered southwestern and northeastern groups along the two mountain ranges, suggesting geography rather than morphology as an important criteria for species delimitation. However, due to the lack of information on the type locality of C. coccinea and the topological complexity of the southwestern area, the taxonomic circumscription of C. coccinea and C. mantiqueirae must be evaluated by additional population sampling. We also propose that the northeastern group comprise at least one distinct species. Also, specimens from Lima Duarte from Serra da Mantiqueira clearly do not belong to neither of the two groups and demand further investigation concerning a possible hybridization scenario of C. coccinea/C. mantiqueirae and C. brevipedunculata. Population genetic patterns of variation are in agreement with pollination observations for this group and with a drift-selection model of speciation. Owing to the high genetic differences among populations, with low levels of variation within populations, conservation priorities should favour protecting as many populations as possible. (AU)