Phylogeny and biogeography of an uncultured clade of snow chytrids

Summary Numerous studies have shown that snow can contain a diverse array of algae known as ‘snow algae’. Some reports also indicate that parasites of algae (e.g. chytrids) are also found in snow, but efforts to phylogenetically identify ‘snow chytrids’ have not been successful. We used culture‐independent molecular approaches to phylogenetically identify chytrids that are common in long‐lived snowpacks of C olorado and E urope. The most remarkable finding of the present study was the discovery of a new clade of chytrids that has representatives in snowpacks of C olorado and S witzerland and cold sites in N epal and F rance, but no representatives from warmer ecosystems. This new clade (‘ S now C lade 1’ or SC 1) is as deeply divergent as its sister clade, the L obulomycetales, and phylotypes of SC 1 show significant ( P  < 0.003) genetic‐isolation by geographic distance patterns, perhaps indicating a long evolutionary history in the cryosphere. In addition to SC 1, other snow chytrids were phylogenetically shown to be in the order R hizophydiales , a group with known algal parasites and saprotrophs. We suggest that these newly discovered snow chytrids are important components of snow ecosystems where they contribute to snow food‐web dynamics and the release of nutrients due to their parasitic and saprotrophic activities.