Abstract Detail

From the backbone to diversification: unraveling the evolutionary history of Ericales

Zhang, Qiong [1], Folk, Ryan [2], Soltis, Douglas [3], Soltis, Pamela [4], Yu, Xiangqin [1].

Generic level relationships, reticulation and whole-genome duplication in Theaceae.

Theaceae, the tea family, comprise nine genera in three tribes and contain more than 300 accepted species of evergreen and deciduous trees and shrubs. Members of Theaceae have great economic and ecological importance, including beverage plants, oil plants and woody ornamentals. A clear phylogenetic framework and well-resolved species level relationships would provide the basis for better utilization and effective protection of plant resources from the tea family. Previous phylogenetic studies based on plastome data resolved the relationships among the three tribes and the intergeneric relationships within two of those tribes. However, generic-level relationships within the largest tribe, Theeae, were not fully resolved. The role of putative whole genome duplication (WGD) events in the family and possible hybridization events among genera within Theeae also remain to be tested further. Here we conducted a comprehensive phylogenomic study of Theaceae based on transcriptomes and low-depth whole-genome sequencing of 57 species as well as additional plastome sequence data. Based on a dataset of low-copy nuclear genes, we reconstructed phylogenetic relationships using concatenated, species tree and phylogenetic network approaches. We further conducted molecular dating analyses and inferred possible WGD events by examining the distribution of the number of synonymous substitutions per synonymous site (KS) for paralogs in each species. For plastid protein-coding sequences (CDS), phylogenies were reconstructed for comparison with the results obtained from analysis of the nuclear dataset. Based on the 610 low-copy nuclear genes (858,606 bp in length) investigated, Stewartieae was resolved as sister to the other two tribes. Within Theeae, the Apterosperma-Laplacea clade grouped with Pyrenaria, leaving Camellia and Polyspora as sister. The estimated ages within Theaceae were largely consistent with previous studies based mainly on plastome data. Two reticulation events within Camellia and one between the common ancestor of Gordonia and Schima were found. All members of the tea family shared two WGD events, an older At-γ and a recent Ad-β; both events were also shared with the outgroups (Diapensiaceae, Pentaphylacaceae, Styracaceae and Symplocaceae). Our analyses using low-copy nuclear genes improved understanding of phylogenetic relationships at the tribal and generic levels previously proposed based on plastome data, but the phylogenetic position of the Apterosperma-Laplacea clade needs to be investigated further. No evidence was found for extensive intergeneric hybridization within Theeae or for a Theaceae-specific WGD event. Land bridges (e.g. the Bering land bridge) during the Late Oligocene may have permitted the intercontinental plant movements that facilitated the putative ancient hybridzation between the common ancestor of Gordonia and Schima, which gave rise to Franklinia, a monotypic genus currently endemic to North America.

1 - Kunming Institute of Botany, Chinese Academy of Sciences, CAS Key Laboratory for Plant Diversity and Biogeography of East Asia, 132# Lanhei Road, Heilongtan, Kunming, Yunnan, 650201, China
2 - Mississippi State University, Biological Sciences, 295 E. Lee Blvd., P.O. Box GY, Mississippi State, MS, 39762, United States
3 - University of Florida, Florida Museum of Natural History,, 3215 Hull Road, P. O. Box 2710, Gainesville, FL, 32611, USA
4 - University Of Florida, Florida Museum Of Natural History, Gainesville, FL, 32611.0, United States

phylogenetic network
nuclear DNA
molecular dating
whole-genome duplication.

Presentation Type: Colloquium Presentations
Number: C3009
Abstract ID:154
Candidate for Awards:None

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