Abstract Detail

Phylogenomics

Schenk, John [1], Kelly, Khadijah [2].

Testing for the Monophyly of the Mentzelia Section Bartonia (Loasaceae) Pinnatisect-Leaved Species with Genome Skimming.

The study of adaptive radiations is a two-edged sword in that they are ideal systems to study rapid speciation, but the rate at which species diversify can limit the accumulation of synapomorphies, making phylogenetic inference problematic. Phylogenetic inference can be further exacerbated by lineage sorting, which can be especially problematic in recent adaptive radiations. Mentzelia section Bartonia (Loasaceae) exemplifies this two-edged sword well, where macroevolutionary studies have determined the clade underwent a recent adaptive radiation, and many phylogenetic relationships remain inconclusive or weakly supported. The most recent phylogenetic hypothesis of the section based on the ribosomal internal and external transcribed spacer regions resolved several deep clades and numerous sister species pairs, but lacked resolution intermediately. Although many relationships were consistent with morphological and geographic similarities, some expected relationships were not recovered. One group in particular, the pinnatisect-leaved species, were recovered in a polytomy, with some species reconstructed as sister to morphologically and geographically dissimilar species. In addition to pinnatisect leaves, the pinnatisect species also share similar floral, fruit, and seed traits, and they are closely distributed near the Four Corners region of the southwestern United States. We attempted to resolve relationships by generating additional sequence variation with the next generation sequencing technique of genome skimming. We sampled 14 species to include those recovered in the pinnatisect polytomy plus outgroups to determine if clades could be robustly resolved. We explicitly tested the hypothesis that pinnatisect species are each other's closest relatives with the approximately unbiased test. Data from the nuclear ribosomal complex recovered a phylogeny that was consistent with a previous hypothesis based on ribosomal spacer regions; however, much greater resolution was identified. Phylogenies based on the chloroplast and mitochondrial genomes, as well as two anonymous nuclear loci were largely discordant. Maximum likelihood analyses based on concatenation and Bayesian species-tree analyses recovered partially incongruent phylogenies, each of which placed the pinnatisect species in three separate clades. The approximately unbiased test rejected the monophyly of the pinnatisect species, suggesting that the pinnatisect form has evolved numerous times. Although genome skimming has provided much greater sequence variation and resolution of strongly supported clades, substantial lineage sorting has likely resulted in discordance among gene trees.

Related Links:
Schenk Lab

1 - Georgia Southern University, Department Of Biology, 4324 Old Register Road, Biological Sciences Building, Statesboro, GA, 30458, United States
2 - Georgia Southern University, Department of Biology, 4324 Old Register Road, Statesboro, GA, 30458, USA

Keywords:
phylogeny
Phylogenomics
genome skimming
Cytonuclear discordance
Mentzelia
Loasaceae
Incomplete Lineage Sorting
Next generation sequencing
convergent evolution.

Presentation Type: Oral Paper
Session: 36, Phylogenomics III
Location: 107/Mayo Civic Center
Date: Wednesday, July 25th, 2018
Time: 8:45 AM
Number: 36004
Abstract ID:794
Candidate for Awards:None