Biogeography of the cosmopolitan sedges (Cyperaceae) and the area-richness correlation in plants

Aim Across angiosperm families, the area occupied by a family is strongly correlated with its richness. We explore the causes of this area-richness correlation using the cosmopolitan family, Cyperaceae Juss., as a model. We test the hypothesis that, despite a proposed tropical origin, temperate lineages in the family diversified at elevated rates. We test the hypothesis that the area-richness correlation is maintained within intrafamilial clades, and that this relationship could be described as a function of niche space. We also test the hypothesis that the partitioning of geographical and ecological space, not the extent of this space, is the factor most closely associated with clade richness.