Abstract Detail


Metzgar, Jordan [1].

Diversification of the fern genus Cryptogramma across time and space.

The parsley ferns (Cryptogramma) are a genus of small, rock-loving ferns in Pteridaceae and are frequently found in climate-sensitive habitats, such as sky islands and glacial margins. This study characterized the evolutionary history of parsley ferns (Cryptogramma) and assessed the impact of climate change impacts in the C. acrostichoides Beringian polyploid complex. Accessions of 15 species in the cryptogrammoid clade (Llavea-Coniogramme-Cryptogramma) within Pteridaceae were sampled to generate DNA sequence data from six plastid loci (rbcL, rbcL-accD, rbcL-atpB, rps4-trnS, trnG-trnR and trnP-petG) and one nuclear locus (gapCp). These data were analyzed to test the monophyly of the genus, assess species boundaries, and reconstruct the parentage of the three known polyploidy parsley fern lineages. Most described species of Cryptogramma reflect generally allopatric reciprocally monophyletic lineages that are independent evolutionary trajectories, with one reticulation event. Divergence time estimates derived using a Bayesian relaxed clock method reveal that intergeneric diversification occurred in the Paleocene and Eocene, while most interspecific cladogenesis was during the climate fluctuations of the Pleistocene. The biogeographic reconstruction revealed that most diversification, including the origin of the cryptogrammoid clade and Cryptogramma, was centered in China and Taiwan.
The Beringian C. acrostichoides complex (C. acrostichoidesC. raddeana, and their allotetraploid, C. sitchensis) is an ideal candidate to study climate change impacts due to their geographic range encompassing many previously-glaciated and refugial areas. ENMs predicting suitable habitat in the present day for each species were generated, then projected our models to the last glacial maximum (LGM; 21kya) using paleo-climate data to analyze the ferns’ response to rapid climate change after the Pleistocene. Models were also projected to future climate scenarios (2070 CE; rcp26, rcp45, rcp60, and rcp85) to identify suitable habitats for each species and focus conservation efforts. Suitable habitat for both parental taxa of Cryptogramma sitchensis occurred in the Aleutians during the LGM and divergence time estimates support a Pleistocene age of this tetraploid. Both the phylogeographic analysis and ecological niche model projections support the in situ survival of C. acrostichoides along ice sheet margins or in microrefugia in the Pacific Northwest throughout the Pleistocene. Future predictions of suitable habitat for this polyploid complex suggests the diploid progenitor species will experience only small range losses due to anthropogenic climate change while their allotetraploid descendent will suffer a massive reduction in suitable habitat within 50 years.

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

ecological niche modelling
divergence time estimation
Last Glacial Maximum.

Presentation Type: Oral Paper
Session: PTER1, Pteridology I
Location: Virtual/Virtual
Date: Monday, July 27th, 2020
Time: 10:15 AM
Number: PTER1002
Abstract ID:118
Candidate for Awards:Edgar T. Wherry award


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