Systematics/Phytogeography / Taxonomie/ Section
Vaezi, Jamil , Brouillet, Luc .
Phylogenetic relationships among diploid species of Symphyotrichum (Asteraceae: Astereae) based on two nuclear markers.
Subtribe Symphyotrichinae (Asteraceae: Astereae) comprises five genera: Canadanthus, Ampelaster, Psilactis, Almutaster, and Symphyotrichum. The majority of the members of the subtribe are North American. Intergeneric and interspecific relationships within the subtribe have been investigated in the past, particularly by Nesom (1994) and Semple (2005), using morphological, cytological, and partly, molecular approaches. Symphyotrichum with ca. 91 species is the largest genus within the subtribe and includes four subgenera: Symphyotrichum (x= 7 and 8), Virgulus (x= 4 and 5), Astropolium (x= 5), and Chapmaniani (x= 7), according to Semple (2005). With high levels of morphological plasticity and interspecific hybridization, and over 50% of polyploid species, Symphyotrichum is a complex genus. In this study we used two nuclear markers, the internal transcribed spacer (ITS) of nrDNA and the low copy nuclear gene glyceraldehyde 3-phosphate dehydrogenase (GAPDH) to resolve intergeneric and interspecific relationships within the subtribe at the diploid level, in order to determine whether our phylogeny validates the classifications of Nesom or Semple. Our results confirm the status of Canadanthus and Ampelaster as independent ganera, whereas Psilactis and Almutaster are part of polytomous branches with Symphyotrichum species and their position is equivocal. Within Symphyotrichum, subg. Virgulus is a monophyletic group based on ITS and appears polyphyletic based on GAPDH. Neither the ITS nor the GAPDH analyses support a distinct status for subg. Astropolium, as it groups within subg. Symphyotrichum. In general, interspecific relationships within Symphyotrichum, and subg. Symphyotrichum in particular, are unresolved and do not reflect fully relationships based on morphological and cytological data. Lack of resolution in Symphyotrichum may be interpreted as a case of recent evolutionary radiation.
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1 - Université de Montréal, Institut de recherche en biologie végétale, 4101 rue Sherbrooke est, Montréal, Québec, H1X 2B2, Canada
Presentation Type: Poster:Posters for Sections
Location: Ball Room & Party Room/SUB
Date: Monday, July 28th, 2008
Time: 12:30 PM