Nazaire, Mare , Hufford, Larry .
The phylogenetic relationships in Mertensia: implications for taxonomy and inferring cryptic diversity.
Mertensia (Boraginaceae), a monophyletic genus composed of approximately 45 species of herbaceous perennials in Asia, North America and circumboreal locales, has presented considerable taxonomic problems. Limited morphological differentiation and continuous variation among taxa contribute to uncertainty about species boundaries and the taxic affiliations of many populations. Our study applies molecular phylogenetic methods to infer evolutionary lineages, address taxonomic circumscription, test hypothesized relationships, and explore cryptic diversity in Mertensia. We used DNA sequence data from 11 chloroplast (cp) regions (matK, ndhF, trnL-trnF, psbJ-petA, rpl32-trnL, trnK-rps16, trnQ-rps16, ycf6-psbM, psbD-trnT, ndhF-rpl32, ndhJ-trnF) to examine evolutionary relationships among 110 accessions that serve provisionally as exemplars of 32 species of Mertensia (sensu Williams 1937; Popov 1953), encompassing 22 species in North America, six in Asia, three in Beringia, and one in coastal circumboreal locales. We recover North American taxa nested in a grade of Asian and circumboreal lineages of Mertensia. Among North American mertensias, the following four clades have moderate to strong support: (1) "ciliata/alpina," (2) "Rocky Mountain/Eastern," (3) "Idaho," and (4) "paniculata." The "ciliata/alpina" clade consists of most M. ciliata and M. alpina accessions and is centered in Colorado. The "Rocky Mountain/Eastern" clade, which is sister to the "ciliata/alpina" clade, is widely distributed and consists of the following two subclades: (1) "Middle/Northern Rockies" (including M. humilis, M. oblongifolia, and M. oreophila), and (2) "Great Plains/Eastern U.S." (including M. lanceolata and M. virginica). The "Idaho" clade includes the narrowly distributed M. campanulata. The "paniculata" clade, which includes accessions of M. paniculata and M. platyphylla, is broadly distributed across the Pacific Northwest, Alaska, and Canada. These preliminary results are discordant with various proposals in taxonomic treatments. For example, M. bella, which Williams (1937) and Povov (1953) placed in a monotypic section Neuranthia is nested among species of section Mertensia. Several broadly circumscribed species from western North America (e.g. M. ciliata, M. lanceolata, M. oblongifolia, M. viridis) are not monophyletic, and we see potential signatures of cryptic taxa among these broadly circumscribed species. These data help to resolve evolutionary relationships within Mertensia and will aid in the taxonomic revision of species within the genus.
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1 - Washington State University, P.O. Box 644236, Pullman, WA, 99164-4236, USA
2 - Washington State University, SCHOOL OF BIOLOGICAL SCIENCES, 312 Abelson Hall, PULLMAN, WA, 99164-4236, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Delaware C/Hyatt
Date: Wednesday, July 11th, 2012
Time: 4:30 PM