Abstract Detail

Systematics Section/ASPT

García, Miguel [1], Costea, Mihai [2], STEFANOVIC, SASA [3].

Phylogeny, character evolution, and biogeography of Cuscuta (dodders; Convolvulaceae).

The parasitic genus Cuscuta, containing some 200 species circumscribed traditionally in three subgenera, is nearly cosmopolitan, occurring in a wide range of habitats and hosts.  Previous molecular studies, on subgenera Grammica and Cuscuta, delimited major clades within these groups.  However, the sequences used were unalignable among subgenera, preventing the phylogenetic comparison across the genus.  We conducted a broad phylogenetic study using rbcL and nrLSU sequences covering the morphological, physiological, and geographical diversity of Cuscuta.  We used a variety of methods to reconstruct phylogeny, ancestral states for taxonomically important characters, and historical biogeography.  Four well-supported major clades are resolved.  Two of them correspond to subgenera Monogynella and Grammica.  Subgenus Cuscuta is paraphyletic, with section Pachystigma sister to subgenus Grammica.  Hybridization may play an important yet underestimated role in the evolution of Cuscuta.  Previously described cases of strongly supported discordance between plastid and nuclear phylogenies, interpreted as reticulation events, are confirmed here and three new cases are detected.  Dehiscent fruits and globose stigmas are inferred as ancestral character states, whereas the ancestral style number is ambiguous.  These results disagree with scenarios of evolution (polarity) previously proposed for several taxonomically important morphological characters, and with their usage and significance.  Biogeographical reconstructions suggest an Old World origin for the genus and subsequent spread to the Americas as a consequence of one long-distance dispersal.  While several cases of long-distance dispersal are inferred, vicariance or dispersal to adjacent areas emerges as the dominant biogeographical pattern.

Related Links:
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Digital atlas of Cuscuta

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

Keywords:
Character evolution
Convolvulaceae
Cuscuta
molecular systematics
nrLSU
parasitic plants
rbcL
reticulate evolution.

Presentation Type: Oral Paper:Papers for Sections
Session: 33
Location: River Fork/Grove
Date: Wednesday, July 30th, 2014
Time: 8:45 AM
Number: 33004
Abstract ID:128
Candidate for Awards:None