The effects of climate change on cytotype distributions of endemic genera in the North American Coastal Plain

Approximately 33% of plant species face extinction due to climate change. Polyploidisation, a process resulting in more than two complete sets of chromosomes, may be promoted by periods of climate fluctuations. Ecological niche modelling (ENM) using occurrences of endemic plants in the North American Coastal Plain (NACP) biodiversity hotspot could be used to evaluate the potential effects of climate change on cytotype distributions. We used known diploid and polyploid taxa endemic to the NACP to test hypotheses that diploids and polyploids differed in habitat preferences, considerable overlap existed between cytotypes, and polyploid distributions would increase under climate change projections. We examined niche identity and overlap of 28 congeneric ploidy level pairs and performed ENM to evaluate how climate change could affect these groups. Congeneric ploidy level pairs differed significantly in niche identity, and overlap varied across genera. Eleven genera showed greater than 100% increases in habitat suitability and six genera showed almost no remaining suitable habitat in at least one future climate scenario. With 70% of the species that showed substantial declines in projected suitable habitat being of conservation concern, we propose that future studies of these genera should be a primary focus in the NACP.