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Abstract Detail

Systematics Section/ASPT

Costea, Mihai [1], García, Miguel [2], Baute, Kurtis [3], Stefanović, Saša [4].

A complicated evolutionary history of Cuscuta pentagona clade (Convolvulaceae) and consequences of ignoring systematics.

The distribution of Cuscuta subg. Grammica, sect. Cleistogrammica (Cuscuta pentagona clade) is centered in North America (C. campestris, C. glabrior, C. harperi, C. 4pentagona, C. obtusiflora, C. plattensis, C. polygonorum, C. runyonii); however, long-distance dispersal was documented to Hawaii (C. sandwichiana), South America (C. gymnocarpa, C. stenolepis, and in part C. obtusiflora), Africa (C. bifurcata, C. schlechteri), Eurasia, and Australia (C. australis). Hybrid speciation was already documented for some members of sec. Cleistogrammica (C. sandwichiana, C. bifurcata) but previous studies strongly suggested that the extent of reticulate evolution is underestimated in Cuscuta generally, and in this section in particular. Sequence data from the nuclear internal transcribed spacer (ITS) and the plastid trnL-F region were used to reconstruct the phylogeny and gain a better understanding of the evolutionary history within the clade. Additionally, a morphometric analysis was conducted to test the phenetic distinctiveness of a select number of species with taxonomic problems: C. pentagona, C. campestris, C. gymnocarpa, and C. glabrior. Discordances between phylogenies derived from plastid and nuclear data showed that C. campestris is a hybrid, likely involving the C. runyonii/glabrior lineage as a maternal progenitor and an undiscovered species as a paternal progenitor. This latter species, an extinct or unsampled lineage, was itself inferred to be a hybrid between C. pentagona/harperi and C. australis/obtusiflora/polygonorum lineages. Both the evolutionary and morphometric results clearly showed that C. campestris is a distinct species and the negative consequences of its amalgamation with C. pentagona during the last decades are discussed. Cuscuta gymnocarpa, an enigmatic species described from specimens collected by Darwin from the Galapagos, was inferred as conspecific with C. campestris and proposed as a variety of the latter. Cuscuta campestris becomes thus one of the first documented invasive species to be introduced to the Galapagos. A new species, Cuscuta modesta, was discovered while studying the systematics of this clade.

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1 - Wilfrid Laurier University, Biology, 75 University Avenue West, Waterloo, Ontario, N/A, N2L3C5, Canada
2 - University of Toronto Mississauga, Biology, 3359 Mississauga Rd., Mississauga, ON, L5L1C6, Canada
3 - Wilfrid Laurier University
4 - University Of Toronto Mississauga, Department Of Botany, 3359 Mississauga Rd, Mississauga, ON, L5L 1C6, Canada

field dodder
Galapagos Islands
homoploid hybridization.

Presentation Type: Oral Paper:Papers for Sections
Session: 60
Location: Salon 2/The Shaw Conference Centre
Date: Wednesday, July 29th, 2015
Time: 8:30 AM
Number: 60003
Abstract ID:112
Candidate for Awards:None

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