Abstract Detail

Systematics

Albal, Asawari [1], Costea, Mihai [2], Stefanovic, Sasa [1].

Species delimitation and phylogenetic relationships in Cuscuta subgenus Monogynella (Convolvulaceae).

Cuscuta (dodders) consists of ~200 species circumscribed into four subgenera (Monogynella, Cuscuta, Pachystigma, and Grammica) and is the only parasitic genus in Convolvulaceae (the morning-glory family). This genus shows a significant diversity in plastid functionality and ability to perform photosynthesis. As such, it represents a rare mixotrophic system within parasitic plants, where different trophic modes can be found at a lower (species) phylogenetic level. Cuscuta species range from chlorophyllous hemiparasitic members of Monogynella, to "cryptically" photosynthetic members of subgenera Cuscuta, Pachystigma, and Grammica, to the two completely non-photosynthetic (holoparasitic) clades within Grammica. Subgenus Monogynella has been included in broad-scale phylogenies, but apart from a few placeholders, this group has not been extensively sampled and studied, neither taxonomically, nor morphologically, nor geographically. This was partly due to the difficulties of obtaining adequate material from Central Asia, the center of diversity of this subgenus. Our current work focuses on molecular studies aimed at delimiting species in Monogynella, using two non-coding sequence regions, trnL-F and nrITS, with specimens encompassing ~3/4 of its known species diversity. Our analyses show highly congruent trees, with similar clades observed using both plastid and nuclear markers, with no indication of hybridization, as has frequently been observed in other subgenera of Cuscuta. Most of the species represented by multiple individuals from various geographic regions, have been found to be reciprocally monophyletic or paraphyletic. Some of the synonymies have also been resolved. However, the backbone relationships within this subgenus remain poorly supported. Also, one major open question is the case of the actual identity and position of C. reflexa; namely, the putative samples of this species are found as three different lineages on the optimal trees, and presently it is not clear which one, if any, corresponds to the type of this species. Further morphological and taxonomic studies, along with in-depth phylogenomics approaches, are needed to resolve these remaining systematics issues.

1 - University of Toronto Mississauga, Department of Biology, 3359, Mississauga Road, Mississauga, Ontario, L5L1C6, Canada
2 - Wilfrid Laurier University, Biology, 75 University Avenue West, Waterloo, ON, N2L 3C5, Canada

Keywords:
Cuscuta
Monogynella
hemiparasitic
Convolvulaceae
species delimitation
parasitic plants.

Presentation Type: Oral Paper
Session: SYSTII, Systematics II: Basal Asterids & Euasterids I
Location: Virtual/Virtual
Date: Tuesday, July 20th, 2021
Time: 1:30 PM(EDT)
Number: SYSTII005
Abstract ID:255
Candidate for Awards:None