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Hasenstab-Lehman, Kristen [1], Guilliams, C. Matt [1], Elvin, Mark [2], McCabe, Stephen [3], Yost, Jenn [4].

Evaluating taxonomic circumscription in the Dudleya cymosa (Crassulaceae) species complex using high-throughput sequencing with an emphasis on rare and potentially undescribed subspecies in Southern California.

Conservation of any group of organisms relies on rigorous taxonomic circumscription and resulting nomenclature to inform on the ground practitioners about taxa that are worthy of conservation action. Phylogenomics can aid with taxonomic circumscription in focal groups that have been recalcitrant in previous studies. Systematics of the charismatic genus Dudleya (Crassulaceae) remains difficult for myriad reasons, including widespread interfertility between congeners, polyploidy, and poor specimen preservation. The genus is distributed from southern Oregon to the tip of the Baja California peninsula, with centers of diversity along coastal southern California and Northern Baja California. Dudleya has garnered media attention in recent years due to several well documented poaching incidents throughout its range, raising concerns of conservationists for rare taxa. The most widespread species, Dudleya cymosa, is a good focal system for phylogenomics, due both to challenging subspecies circumscriptions along with conservation issues such as poaching, habitat loss, and global climate change. This species is restricted to the California Floristic Province, with members growing mostly on rocky, often vertical outcrops. It contains eight recognized subspecies, three of which occur in the Santa Monica Mountains and are federally listed as threatened or endangered: D. cymosa subsp. agourensis, D. cymosa subsp. marcescens, and D. cymosa subsp. ovatifolia. Additional, geographically cohesive morphological variation within D. cymosa in southern California may suggest plants that warrant taxonomic recognition. In this study, a large high-throughput SNP dataset was generated using a double digest Restriction site Associated DNA sequencing (ddRAD) approach for Dudleya, with an emphasis on D. cymosa. We inferred phylogeny using widespread geographic sampling of each of the currently recognized taxa in D. cymosa, putative morphological variants, and relatives throughout the genus. We used the resulting phylogeny to assess the current taxonomic circumscriptions of the D.cymosa subspecies, along with putative new taxa. Our results revealed two broad geographic clades within the D. cymosa. We find support for a taxonomic split in subsp. ovatifolia, elevating the conservation importance of the two populations remaining in that taxon. Our study also demonstrates the importance of comprehensive study for taxa of conservation concern that involves fieldwork, morphological observation, and further genomic analyses. These multi-disciplinary approaches are necessary to generate meaningful conservation outcomes for imperiled taxa.

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1 - Santa Barbara Botanic Garden, Conservation and Research , 1212 Mission Canyon Rd, Santa Barbara, CA, 93105, USA
2 - U.S. Fish & Wildlife Service, 2493 Portola Road, Suite B, Ventura, CA, 93003, USA
3 - University of California Santa Cruz, Arboretum , Santa Cruz, CA, 95064, USA
4 - Ecology And Evolutionary Biology, 1243 Palm St, San Luis Obispo, CA, 93401, United States


Presentation Type: Oral Paper
Session: PHYLOV, Phylogenomics V
Location: Virtual/Virtual
Date: Friday, July 23rd, 2021
Time: 4:15 PM(EDT)
Number: PHYLOV006
Abstract ID:1040
Candidate for Awards:None

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