Abstract Detail

Pteridology

The systematics, biogeography, and Pleistocene refugia of the parsley ferns (Cryptogramma).

The parsley ferns (Cryptogramma) are a small, circumboreal genus of rock ferns in the basal clade of the large, varied family Pteridaceae. These ferns have diversified since the Oligocene and frequently occupy habitats vulnerable to climate change, such as sky islands and glacial margins. I resolved the evolutionary history of the group and clarified the origins of polyploid taxa using plastid and nuclear DNA markers. Cryptogramma is most closely related to Coniogramme and is comprised of the reciprocally monotypic sections Cryptogramma sect. Homopteris and sect. Cryptogramma. I inferred divergence time estimates for key nodes using Bayesian analysis of the plastid data set coupled with secondary time constraints to reveal that crown group Cryptogramma began diversifying in the Oligocene, with most present-day species originating in the Pliocene and Pleistocene. The likelihood-based ancestral area reconstruction of the chronogram and geographic distribution data supports an east Asian origin of Cryptogramma, with subsequent colonization of the New World and Europe. I found no significant changes in speciation rate across time or the phylogeny using speciation rate analysis and suggest that Cryptogramma could represent an example of morphological stasis, with cold-hardiness adaptations for boreal habitats. I then used the Beringian C. acrostichoides complex as a test case to assess climate change-related impacts on these cold-adapted taxa. Presence data for the diploid species C. acrostichoides and C. raddeana, as well as their allotetraploid, C. sitchensis, were coupled with WorldClim bioclimatic variables in Maxent to generate ecological niche models (ENMs) predicting suitable habitat in the present day for each species. These ENMs were projected to the Last Glacial Maximum (LGM; 21kya) to identify Pleistocene refugia and the ENMs were also projected to future climate scenarios to assess potential habitat loss for each species. Refugia in southcentral Alaska and the coastal Pacific Northwest during the LGM likely supported populations of both C. acrostichoides and C. sitchensis. Southern populations of C. acrostichoides are at elevated risk of habitat loss in the near future and C. sitchensis will potentially suffer dramatic habitat loss. I independently assessed the hypothesized LGM refugia by reconstructing the phylogeographic history of C. acrostichoides and C. sitchensis during the Pleistocene and Holocene. These results also support the long-term presence of C. acrostichoides and C. sitchensis in southcentral Alaska, the coastal Pacific Northwest, and unglaciated portions of the western contiguous USA. The long-term persistence of these taxa through dramatic climatic cycles in northwestern North American refugia shows that these locations may be vital to their survival from the impacts of anthropogenic climate change.

1 - Virginia Tech, Biological Sciences, 926 W. Campus Dr, MC 0406, Derring Hall 2119, Blacksburg, VA, 24061, United States

Keywords:
Cryptogramma
ecological niche modelling
divergence time estimation
polyploidy
climate change.

Presentation Type: Oral Paper
Number: PTR1001
Abstract ID:1062
Candidate for Awards:Edgar T. Wherry award