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Cohen, Dylan [1], Poston, Muriel [2], McDade, Lucinda [1].

Consequences of glaciation in the southern Andes Mountains: Phylogenetic relationships of Pinnasa, and patterns of migration, isolation, and secondary contact in the Pinnasa pinnatifida complex (Loasacea.

Throughout the Pleistocene and into the mid-Holocene, repeated cycles of glaciation altered landscapes, in turn influencing plant distributions and patterns of genetic diversity in the northern and southern hemispheres. Plants were forced to migrate to lower elevations, remain on the peripheries of montane systems, or persist in nunataks and refugial areas. The northern hemisphere holds more overall landmass compared to the southern, and the impact of glaciers there has been well studied with a central focus on understanding biological repercussions. The southern hemisphere has been the focus of less research, although the southern Andean range presents a unique geographic system to test hypotheses surrounding impacts of glaciation on plant diversity and population structure. The southern Andes are a north to south mountain chain with a topography of high peaks and low valleys that provide habitat for alpine and montane plants. Pinnasa (Loasaceae) is endemic to the southern Andes and adjacent Patagonian Steppe. Species limits are contentious leading taxonomists to include anywhere from four to 20 species. Molecular phylogenetics has been useful in segregating Pinnasa from Loasa, but studies have included only four samples, and left doubts about species diversity. In the first part of this paper, I test species hypothesis and investigate their evolutionary relationships using phylogenomic methods. Next, I address historical events that have shaped present day genetic diversity within and among populations of the Pinnasa pinnatifida complex. I generated Restriction site associated DNA sequence (RADSeq) data to 1) address species hypotheses, 2) place species into an evolutionary context, and 3)  understand the genetic diversity and demographic history of the P. pinnatifida complex. Molecular results supported, and morphology confirmed, the reestablishment of Pinnasa amabilis, and increases evidence for "Loasa" caespitosa to be transfered into Pinnasa. Population analyses identified three genetically distinct regions along the southern Andes that may have served as climate refugial areas from the time of the Greatest Patagonian Glaciation to the Last Glacial Maximum. After glaciers receded, it appears that secondary contact occurred multiples times between the northern and central Andean clusters, as well as between central and southern groups, as suggested by increased genetic diversity and mixed ancestry. Several species are confirmed and some, such as P. kurtzii and the P. pinnatifida complex, need more sampling for conclusive results. Finally, this study contributes novel results to the limited, but growing body of research to understand the genetic consequences of glaciation in the southern Andes.

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1 - California Botanic Garden, 1500 North College Avenue, Claremont , CA, 91711, USA
2 - Pitzer College, Environmental Analysis, 1050 North Mills Avenue, Claremont, CA, 91711, USA

species complex
southern Andes Mountains

Presentation Type: Oral Paper
Session: COOLI, ASPT Cooley Award Talks I
Location: Virtual/Virtual
Date: Wednesday, July 21st, 2021
Time: 10:00 AM(EDT)
Number: COOLI001
Abstract ID:254
Candidate for Awards:George R. Cooley Award

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