Master of Science (MSc)
Faculty of Science
Dr. Mihai Costea
The genus Cuscuta (Dodder; Convolvulaceae) are obligate parasitic plants. In one clade known as section Indecorae, there are species which are considered pests that pose significant threats to agricultural crop production, while other species are rare or known only from historical records. Section Indecorae contains three species: C. coryli, C. warneri, and C. indecora (the latter with three infraspecific taxa: var. indecora, var. longisepala, and var. attenuata). The systematics of section Indecorae are not currently resolved. Cuscuta indecora has a long and complicated taxonomic history with many infraspecific varieties described, and recent phylogenetic analyses using molecular data inferred species level paraphyly and infraspecific level polyphyly, strongly suggesting that species limits and infraspecific variation should be reconsidered in this species. The objectives of my study were to characterize phylogenetic relationships within section Indecorae and test whether geographic range is related to genetic separation; conduct a morphometric analysis to assess morphological patterns and compare the results to the newly generated phylogeny; and conduct ecological studies using herbarium specimens and field surveys to expand the geographic, host and habitat range of section Indecorae. Results indicated that C. warneri is a distinct species using molecular, morphometric, and ecological analysis. Cuscuta coryli is a distinct species nested within a clade of C. indecora, therefore C. indecora is a paraphyletic species, and C. coryli is its derivative. Cuscuta indecora s.l. is confirmed at species level based on molecular and morphological evidence. Two clades of C. indecora were identified by the phylogeny; however, these clades did not correspond to the accepted varieties of C. indecora, and did not demonstrate morphological, ecological, or geographic distinctiveness. Based on this evidence, C. indecora s.l. is tentatively conserved as one morphologically variable, paraphyletic species. Cuscuta indecora’s infraspecific ranks of C. indecora were not separated by the phylogenetic or morphometric analyses, and have broad geographic and host range overlap. Therefore, infraspecific ranks were not recognized anymore. Additionally, new geographic records for C. coryli and a new insect-plant interaction are reported.
Burt, Corey, "Discerning Friend From Foe: Systematic Revision of Cuscuta L. Section Indecorae Using A Combined Ecological, Morphometric, and Phylogenetic Approach." (2023). Theses and Dissertations (Comprehensive). 2509.
Available for download on Wednesday, September 20, 2023