Diversity trends of bryophytes in continental Antarctica.

Bryophytes exhibit a decline in species richness with latitude across the sub-Antarctic islands, Antarctic Peninsula and Antarctic continent, but not within the Antarctic continent itself. We analyzed diversity and biogeographic patterns of bryophytes at intra-regional scale across the Ross Sector of continental Antarctica, also comparing the "coast" and "slope" provinces within this region, and placed these patterns in the context of bryophyte biogeography across Antarctica. Our study area included 63 sites along a transect through Victoria Land and the Transantarctic Mountains. Distributions of bryophyte species were collated from recent field surveys, the Antarctic Plant Database and the literature. Data analyses included rarefaction, hierarchical classification, multivariate analyses and description of richness trends by latitude bands. Despite an almost linear climatic gradient, bryophyte diversity in the Ross Sector is not influenced by latitude, and patterns differ depending on the scale of analysis. At local scale, diversity "hot spots" appear to be related to favorable local microclimatic conditions. At intra-regional scale, site location in the coast or slope province is the most effective predictor of bryophyte diversity. The site clustering within each province is consistent with precipitation and biogeographic separation of two sub-regions due to important dispersal barriers, as also reported for the microarthropod fauna. At continental scale, bryophyte diversity patterns among sectors suggest a continent-Antarctic Peninsula separation, consistent with the Gressitt Line, suggesting a common feature in the evolutionary history of the vegetation and invertebrate fauna. The high similarities of the floras of adjacent continental sectors suggest a potential route for bryophyte dispersal along the coast of continental Antarctica.