Niche shifts after long-distance dispersal events in bipolar sedges (Carex, Cyperaceae)

PREMISE OF THE STUDY: Bipolar species represent the greatest biogeographical disjunction on Earth, raising many questions about the colonization and adaptive processes behind such striking distribution. We investigated climatic niche differences of five Carex bipolar species in North and South America to assess niche shifts between these two regions. Moreover, we assessed potential distribution changes with future climate change. METHODS: We used 1202 presence data points from herbarium specimens and 19 bioclimatic variables to assess climatic niche differences and potential distributions among the five species using ordination methods and Maxent. KEY RESULTS: The niche overlap analyses showed low levels of niche filling and high climatic niche expansion between North and South America. Carex macloviana and C. maritima showed the greatest niche expansion (60% and 96%, respectively), followed by C. magellanica (45%) and C. microglochin (39%). Only C. canescens did not colonize new environments (niche expansion = 0.2%). In contrast, all species but C. magellanica had niche filling that was