Allopolyploidy, Diversification, and the Miocene Grassland Expansion

Authors

Matt Estep
Michael McKain
Dilys Diaz
Jinshun Zhong, University of Missouri–St. Louis
John Hodge
Trevor Hodkinson
Daniel Layton
Simon Malcomber
Rémy Pasquet
Elizabeth Kellogg, University of Missouri–St. Louis

Document Type

Article

Abstract

The role of polyploidy, particularly allopolyploidy, in plant diversification is a subject of debate. Whole-genome duplications precede the origins of many major clades (e.g., angiosperms, Brassicaceae, Poaceae), suggesting that polyploidy drives diversification. However, theoretical arguments and empirical studies suggest that polyploid lineages may actually have lower speciation rates and higher extinction rates than diploid lineages. We focus here on the grass tribe Andropogoneae, an economically and ecologically important group of C4 species with a high frequency of polyploids. A phylogeny was constructed for ca. 10% of the species of the clade, based on sequences of four concatenated low-copy nuclear loci. Genetic allopolyploidy was documented using the characteristic pattern of double-labeled gene trees. At least 32% of the species sampled are the result of genetic allopolyploidy and result from 28 distinct tetraploidy events plus an additional six hexaploidy events. This number is a minimum, and the actual frequency could be considerably higher. The parental genomes of most Andropogoneae polyploids diverged in the Late Miocene coincident with the expansion of the major C4 grasslands that dominate the earth today. The well-documented whole-genome duplication in Zea mays ssp. mays occurred after the divergence of Zea and Sorghum. We find no evidence that polyploidization is followed by an increase in net diversification rate; nonetheless, allopolyploidy itself is a major mode of speciation.

Publication Date

10-6-2014

Publication Title

Proceedings of the National Academy of Sciences of the United States of America

Volume

111

Issue

42

First Page

15149

Last Page

15154

DOI

10.1073/pnas.1404177111

Recommended Citation

Estep, Matt; McKain, Michael; Diaz, Dilys; Zhong, Jinshun; Hodge, John; Hodkinson, Trevor; Layton, Daniel; Malcomber, Simon; Pasquet, Rémy; and Kellogg, Elizabeth, "Allopolyploidy, Diversification, and the Miocene Grassland Expansion" (2014). Biology Department Faculty Works. 57.
DOI: https://doi.org/10.1073/pnas.1404177111
Available at: https://irl.umsl.edu/biology-faculty/57