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October 20, 2014
 
 
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Mihai Costea

Phylogeny, character evolution, and biogeography of Cuscuta (dodders; Convolvulaceae) inferred from coding plastid and nuclear sequences. American Journal of Botany.


García, M. A., Costea, M., Kuzmina, M., & Stefanović,, S.

published: 2014 | Research publication | Cuscuta

Premise of the study: 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.

Methods: We conducted a broad phylogenetic study using rbcL and nrLSU sequences covering the morphological, physiological, and geographical diversity of Cuscuta. We used parsimony methods to reconstruct ancestral states for taxonomically important characters. Biogeographical inferences were obtained using statistical and Bayesian approaches.

Key results: 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. 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. Biogeographical reconstructions suggest an Old World origin for the genus and subsequent spread to the Americas as a consequence of one long-distance dispersal.

Link to full paper (including supplemental material)

revised Apr 8/14

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