Abstract Detail

Systematics

Columbus, J. Travis [1], Mills, Carolyn [2], Fraga, Naomi [2].

Phylogenetics of the Oxytheca clade (Polygonaceae, Eriogoneae) based on ddRADseq data.

Kempton's (2012) phylogenetic study of Eriogoneae (Systematic Botany 37: 723-737), based on one nuclear locus and two chloroplast loci, revealed an early diverging, strongly supported clade (Oxytheca  clade) comprising  Acanthoscyphus  (1 sp.),  Aristocapsa  (1),  Centrostegia  (1),  Dodecahema  (1),  Mucronea  (2),  Oxytheca  (3),  Systenotheca  (1), and two species of  Eriogonum. All are annuals primarily distributed in California, and most have limited distributions. Except for the species of  Eriogonum, all possess involucral projections (awns) that differ in position, number, and form. Because a number of relationships within the  Oxytheca  clade were poorly supported in Kempton's study, and the genus  Oxytheca  did not resolve as monophyletic, we have built on her study by sampling multiple populations per species and employing double-digest reduced representation sequencing (ddRADseq). Our overarching goal was to achieve a robust estimate of the phylogeny. Specific questions included: Are the taxa monophyletic? Did possession of involucral awns evolve more than once? What were the evolutionary transitions in leaf, involucral, and floral form? We expanded sampling to include additional, morphologically similar, and previously unsampled species of  Eriogonum. Analysis of the ddRADseq data yielded a highly resolved and supported tree. Most taxa are monophyletic, including  Oxytheca. A notable exception is  Eriogonum, which forms a grade and is known from other studies not to be monophyletic. In addition to the two species sampled by Kempton, our analyses show that five other species of  Eriogonum  are members of the  Oxytheca  clade. Possession of involucral awns is inferred to have evolved once, followed by significant diversification in position, number, and form. In addition to apical awns, the sister genera  Centrostegia  and  Dodecahema  share basal awns. We are investigating how variation in morphology and reproductive biology (little known) relates to habitat and distribution, as some taxa (e.g.,  Centrostegia,  Oxytheca perfoliata) are widespread whereas others (e.g.,  Aristocapsa,  Dodecahema) are more narrowly distributed.

1 - California Botanic Garden, 1500 North College Avenue, Claremont, CA, 91711, USA
2 - California Botanic Garden, 1500 North College Avenue, Claremont , CA, 91711, USA

Keywords:
phylogenetics
Polygonaceae
Eriogonum
involucre
Systematics.

Presentation Type: Oral Paper
Session: SYSTIV, Systematics IV: Eurosids & Basal Asterids
Location: Virtual/Virtual
Date: Wednesday, July 21st, 2021
Time: 4:15 PM(EDT)
Number: SYSTIV006
Abstract ID:910
Candidate for Awards:None