E&E PhD Dissertation Seminar: Phylogenomic systematics of lobariod lichens: diversification and population genetics, Todd Widhelm
March 15, 2019
12:00 PM - 1:00 PM
Faculty Advisors: Roberta Mason-Gamer and Thorsten Lumbsch (Field Museum)
Abstract: This seminar covers two dissertation chapters that utilized genomics to understand (1) the diversification of the lobariod clade of lichens and (2) population genetics of one lobariod species, Pseudocyphellaria glabra. For the diversification study, a target enrichment approach of 400 single-copy nuclear genes was used to investigate the phylogenetic relationships and divergence times of 13 genera in the lobariod clade. There was incongruence among sequence data types (nucleotide vs. amino acid sequences) and with different methods of phylogenetic reconstruction (species tree vs. concatenation). Furthermore, evidence for rapid and reticulate evolution based on extremely short branches leading to the diversifications among the focal genera was discovered. The use of target-capturing data allowed for the exploration of the mechanisms underlying phylogenetic and systematic incongruence. The population genetic study focuses on P. glabra, a species that has a disjunct distribution, occurring in Australia, New Zealand, and southern South America. Restriction site-associated DNA sequences were obtained from 286 samples collected throughout its entire range to conduct population genomic analyses. Two hypotheses were tested; (1) if large bodies of water isolate populations of P. glabra, then these populations will be genetically distinct, and (2) given the strong wind patterns in the southern hemisphere, P. glabra populations on different landmasses will be connected by long-distance dispersal (i.e. gene-flow). The results suggested that populations from Australia, Chile, and New Zealand are genetically distinct, but frequent long-distance dispersal may sufficiently prevent speciation.
Date posted
Jan 28, 2019
Date updated
Mar 7, 2019