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Abstract Detail

Systematics Section/ASPT

Schneider, Adam [1], Freyman, William [1], Guilliams, C. Matt [2], Springer, Yuri P. [3], Baldwin, Bruce G. [1].

Divergence times in Linaceae and the recent, rapid serpentine radiation Hesperolinon.

Hesperolinon (Linaceae) is a genus of dwarf flax found in the western United States. It consists of 12-13 species, with a center of diversity in Lake and Napa counties, California. Nested within the paraphyletic genus Linum, Hesperolinon is noted for its unique petal attachment and appendages, and ecological affinity to serpentine soils. Recent studies employing a phylogenetic approach have focused on disease ecology and edaphic associations in the genus or its placement within the Linaceae. However, the lack of a well-resolved species-level phylogeny warrants additional study, particularly given longstanding hypotheses by Raven and Axelrod and Helen Sharsmith suggesting cryptic diversity and neoendemism in one of California's largest serpentine radiations. Here, we present both a taxonomically and geographically well-sampled genus-wide phylogeny based on nuclear and cpDNA. To test divergence times in Hesperolinon and related groups, we also present a fossil-calibrated analysis of Linaceae based on publically available Genbank sequences, extending previous work by McDill and colleagues. We estimate that Hesperolinon diverged from its sister group, the monotypic genus Sclerolinon, six million years ago, with most of the diversification within the group taking place more recently (Hesperolinon were not found to be monophyletic in spite of well-marked morphological differences. This incongruence is consistent with recent divergence times for the clade, though in some in some cases (e.g. H. disjunctum) this may be due to undescribed diversity. More broadly, we infer that the common ancestors of Linaceae and its sister group Ixonanthaceae diverged about 79 Ma, with a Linaceae crown age of 44 Ma. Linum was found to be strongly paraphyletic, though the taxonomic sections within this genus are monophyletic with the exception of Linum sect. Linopsis. In addition to the recent radiation of Hesperolinon, the paleotropic genus Hugonia seems to be a parallel example of rapid radiation, diversifying in the last 4 million years.

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1 - University of California, Berkeley, Integrative Biology and Jepson Herbarium, 1001 Valley Life Sciences Building, Berkeley, CA, 94720, USA
2 - Santa Barbara Botanic Garden, 1212 Mission Canyon Road, Santa Barbara, CA, 93105, USA
3 - National Ecological Observatory Network, 1685 38th St. Suite 100, Boulder, CO, 80301, USA


Presentation Type: Oral Paper:Papers for Sections
Session: 31
Location: Salon 4/The Shaw Conference Centre
Date: Tuesday, July 28th, 2015
Time: 10:45 AM
Number: 31011
Abstract ID:988
Candidate for Awards:George R. Cooley Award

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