Perspectives on Carex diversity: from global phylogeny to community assembly
Guest lecture by Associate professor Marcia J. Waterway, McGill University - Montreal, Québec
Carex, a nearly cosmopolitan genus with 2000+ species, is an ideal model system for studying patterns of diversity, evolution, diversification, niche evolution, and biogeography. These sedges are most common in wetland and woodland habitats in temperate, boreal, and arctic regions but also occur in subtropical areas where they are generally found at higher elevations. A robust phylogeny is a prerequisite for such studies. In this presentation, I will show the progress made on the phylogenetic hypothesis both in my lab and by the Global Carex Group. A 9-gene tree with 250 species representing nearly all sections and most geographic regions is strongly supported at nearly all nodes. It gives an overall picture of relationships, and indicates that most traditional sections are poly- or paraphyletic. The GCG megaphylogeny greatly expands the sampling to almost 60% of the species, but uses only ITS, ETS and matK data, providing enough information for reclassification of Carex at the sectional level. Detailed mapping of specimen data in North America reveals contrasting patterns of diversity among the three major clades found there, and intriguing patterns of distribution of individual clades suggest continental radiations, especially in clades that predominate in woodland habitats. Examples from the Laxiflorae-Paniceae-Bicolores clade demonstrate niche differentiation in both woodland and wetland habitats. Studies of co-occurrence at both large scales (between habitats) and small scales (small quadrats within habitats) illustrate the effects of Carex diversification on community assembly in forests and fens. Continuing work compiling data on geographic distribution, environmental tolerances, and traits of Carex species in the context of the developing phylogeny will contribute to our understanding of the evolution and maintenance of diversity in this remarkable genus.
About the speaker
Waterway's research interests are plant systematics, phylogeny and ecological genetics. One focus of her research program is to understand the patterns of species diversity and genetic diversity in plants in relation to the environments in which they grow, using the genus Carex as a model system.