| Summary: | The objective of this study is to assess current distributional patterns of species within a community, while taking into account species' evolutionary histories, as reflected in their phylogenetic relationships. The hypothesis is that closely related species segregate along environmental gradients, either due to historic evolutionary divergence of their niches, or to ecological processes presently occurring within a community. Distribution along environmental gradients was compared to phylogenetic structure of the 27 sedge species (Cyperaceae) growing in the subarctic fen communities of Schefferville, northern Quebec. Field data suggest that within these fens, sedges mostly differentiate along gradients of rooting depth and pH. Species growing in similar (micro)habitats often belong to different taxonomic sedge clades, and species belonging to the same clade usually differentiate on at least one environmental gradient. Further comparison of natural distribution to responses under greenhouse experimental conditions for four selected Carex species suggests that the two relatives in section Limosae differ in their tolerance ranges to environmental conditions due to past evolutionary events, while the two members of section Paniceae differentiate along environmental gradients in nature due to ongoing ecological processes.
|
|---|