Abstract Detail

Systematics

Majumder, Farhan Karim [1], Mathews, Sarah [2], Stefanovic, Sasa [3].

Species Delimitation and Phylogenetic Reconstruction of the Hemiparasitic Genus Cassytha (Lauraceae).

Parasitism has evolved in angiosperms at least 12 times, resulting in similar morphological, cellular, and genetic changes in these organisms. One such example is Cassytha, the only parasitic genus of Lauraceae. Cassytha is a vine-like twining obligate hemiparasite, that attaches to its host and uses its haustoria to graft to the vascular tissue of the host to acquire nutrients and water. Nearly all (18 of 20) currently recognized species are found in Australia. One species, C. filiformis, (in addition to being found in Australia) is circum-equatorial, and two species are found in southern Africa. The delimitation of species within Cassytha, their phylogenetic relationships, and the position the genus within the family remain poorly understood. The last comprehensive work on this group was conducted by Weber (1981), using chiefly reproductive morphology to delimit the species. Weber did not propose any subgeneric divisions, and since then, this genus has not been subject to exhaustive taxonomic work. More recent molecular work focused mainly on trying to find the position of Cassytha within Lauraceae, and sampled only one to few placeholder species. Our current work uses a combination of plastid and nuclear non-coding sequences on an extensive sample of Cassytha species/individuals that capture its taxonomic, morphological, and biogeographical diversity. Such a broad sample will allow us to delimit species, and compare and contrast these results with the body of morphological work that has been compiled on Cassytha. Currently, we are in the process of constructing phylogenies using the multiple plastid sequences. Through the extraction and alignment of sequences from over 150 individuals, we have built a nascent tree that comprises nearly all currently accepted Cassytha species. The majority of species form clades with high bootstrap support, whereas a few require further data to resolve their relationships.

1 - University of Toronto, Department of Ecology and Evolutionary Biology, 25 Willcocks Street, Toronto, ON, M5S 3B2, Canada
2 - Louisiana State University, Biological Sciences, 202 Life Sciences Building, Baton Rouge, LA, 70803, United States
3 - University Of Toronto Mississauga, Department Of Biology, 3359 Mississauga Rd, Mississauga, ON, L5L 1C6, Canada

Keywords:
Cassytha
Lauraceae
phylogenetics
parasitic plants
molecular evolution
Sanger sequencing
Plastomes
plant systematics
Plastid
Molecular Systematics.

Presentation Type: Oral Paper
Session: SYSTIII, Systematics III: Algae to Lilioid Monocots
Location: Virtual/Virtual
Date: Tuesday, July 20th, 2021
Time: 4:30 PM(EDT)
Number: SYSTIII007
Abstract ID:314
Candidate for Awards:None