Assembly of the Arctic flora: Highly parallel and recurrent patterns in sedges (Carex)
2017
Hoffmann, Matthias H. | Gebauer, Sebastian | von Rozycki, Torsten
PREMISE OF THE STUDY: Understanding the origin of ecosystems and their changes through time is important. Two mutually contrasting types of grasslands existed in the Arctic: dry‐ and cold‐adapted grasslands of the Pleistocene dominated by Poaceae species, and presently dominating graminoid grasslands composed of sedges and rushes. We studied the taxon recruitment of the Arctic flora for Carex, the most species‐rich and widespread genus of the Arctic. In this study we explore the possible geographical and altitudinal origins of the species, their ecological provenance in terms of soil moisture and light requirements, and salt tolerance. METHODS: We addressed these questions in a phylogenetic context using the latest megaphylogeny of Carex comprising almost all Arctic species and about half of the genus’ total species diversity. Ecological data were extracted from the literature and analyzed for each clade comprising Arctic species. KEY RESULTS: Arctic Carex species were observed in 48 independent lineages. Almost all areas north of the meridional zone of the Northern Hemisphere may have served as sources of Arctic lineages. Source areas are unrelated to the distribution within the Arctic. Arctic species evolved in lowland and high mountain clades; mostly in wet, rarely in dry adapted clades that occur principally in open conditions. Salt tolerant Arctic species occur in five clades. CONCLUSIONS: Many independent lineages of different geographical areas and ecological backgrounds provided species for the northernmost ecosystem; clear main sources were not discernible. Carex shows the whole dynamic of ecosystem assembly from a seemingly simple immigration of preadapted species, evolution in geographical distant areas, to species radiations in the North.
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