Scientific Area
Abstract Detail
Nº613/1239 - Niche partitioning or divergence? Sister-lineage comparisons reveal complex patterns of niche evolution in Carex
Format: ORAL
Authors
Daniel Spalink
Affiliations
Texas A&M University, College Station, Texas, USA
Abstract
With over 2000 species, Carex (Cyperaceae) is a nearly cosmopolitan genus with centers of diversity in temperate zones of each hemisphere. Carex exhibits tremendous ecological diversity, occupying habitats from coasts to mountaintops, deserts to wetlands, tundra to the tropics, and savannas to forest understories. Divergence across these ecological gradients has long been hypothesized to be a key driver of diversification in Carex. This hypothesis has been supported by phylogenetic comparative analyses, which show strong relationships between rates of speciation and niche evolution across the genus. These analyses to date have been based almost exclusively on the estimations of species niches from occurrence records, which are known to contain biased, missing, and incorrect data. Potentially more pernicious problems, however, are that 1) species distributions are dynamic through time; and few species likely 2) occupy the full extent of their fundamental niches or 3) occur in all geographic areas that are ecologically suitable. Consequently, significant findings of niche evolution in Carex may be spurious. Here, we use emerging methods that avoid the assumption that present distributions represent the full occupancy of species potential ranges. For nearly 500 sister-species pairs, we perform the Niche Overlap Test, which calculates niche similarity between two species in their total occupied environmental space, and the Niche Divergence Test, which calculates niche similarity in the subset of environmental space that is shared and accessible to both species. These tests are designed to detect whether species occupy distinct niches or simply have access to different environments. We then test whether significant niche evolution between sister species is related to their time since divergence, trait divergence, latitude, and total range size.