Scientific Area
Abstract Detail
Nº613/1254 - Tackling tough taxonomy: genomic, morphological, and ecological approaches to Asclepias (Apocynaceae) in North America
Format: ORAL
Authors
Mark Fishbein1, Shannon C. K. Straub2, Victor Andreev1,3, Julien Boutte4, Carl Wagner2, David Kunkel1, Therese Mandracchia2, Alessandra Bryan2, James Riser5
Affiliations
1 Oklahoma State University, Stillwater, USA
2 Hobart and William Smith Colleges, Geneva, USA
3 University of Arizona, Tucson, USA
4 A2Bio2, Molleges, France
5 University of Wisconsin-Platteville, Platteville, USA
Abstract
Rapid diversification may present taxonomic challenges resulting from the gradual nature of speciation. Processes including incomplete fixation of ancestral polymorphisms and partial establishment of reproductive barriers permitting gene flow after speciation result in conflicting information about species boundaries and phylogeny. The rapid diversification of 130 species of AmericanAsclepiasprovides a good system to demonstrate that integration of genomic data, population genetics, ecological modeling, and traditional approaches can resolve longstanding taxonomic challenges. We present two case studies. The dwarf milkweed clade has been variously treated as 1-4 species (A. eastwoodiana, A. ruthiae, A. sanjuanensis, A. uncialis) distributed across semiarid western North America. Populations exhibit limited morphological variation, largely in the shape and vestiture of leaves. Previous research supported recognition of four species based on population genetics and ecological niche modeling. We support this taxonomy with a plastome phylogeny and newly discovered floral differences and resolve the phylogeny of the four species using sequence data from 2000 nuclear genes. In the second example we address circumscription ofA. hirtellaandA. longifolia. Populations of these taxa are found in the eastern United States, with coastal populations assigned toA. longifoliaand interior populations toA. hirtella(orA. longifoliasubsp.hirtella). In the western Gulf Coast (Texas and Louisiana) populations are morphologically intermediate and have been commonly assigned toA. longifolia, which they most resemble. Using population genomic data from 1400 SNP loci and a plastome phylogeny, we found evidence for two largely discrete gene pools. However, the western Gulf Coast populations belong to the interiorA. hirtella, not the coastalA. longifolia, and we present supporting morphological evidence for this circumscription. These case studies pave the way for achieving deeper understanding of evolutionary and biogeographic history ofAsclepias.