Polyploidy and angiosperm diversification

TLDR

Polyploidy is a major, ubiquitous force in angiosperm evolution, with ancient whole‑genome duplications identified across basal lineages and a proposed paleohexaploid near the eudicot split, yet no evidence of WGD has been found in *Amborella*. The study seeks to determine how many polyploidy episodes characterize each lineage and to evaluate whether genome doubling has driven the dramatic species‑richness increases observed in Poaceae, Solanaceae, Fabaceae, and Brassicaceae. The authors employ new computational algorithms capable of reconstructing ancestral genomes to detect and date polyploidy events across deep angiosperm divergences. These algorithms show promise for reconstructing ancestral eudicot and even ancestral angiosperm genomes, providing a framework for mapping ancient polyploidy events.

Abstract

Polyploidy has long been recognized as a major force in angiosperm evolution. Recent genomic investigations not only indicate that polyploidy is ubiquitous among angiosperms, but also suggest several ancient genome-doubling events. These include ancient whole genome duplication (WGD) events in basal angiosperm lineages, as well as a proposed paleohexaploid event that may have occurred close to the eudicot divergence. However, there is currently no evidence for WGD in Amborella, the putative sister species to other extant angiosperms. The question is no longer "What proportion of angiosperms are polyploid? " but "How many episodes of polyploidy characterize any given lineage?" New algorithms provide promise that ancestral genomes can be reconstructed for deep divergences (e.g., it may be possible to reconstruct the ancestral eudicot or even the ancestral angiosperm genome). Comparisons of diversification rates suggest that genome doubling may have led to a dramatic increase in species richness in several angiosperm lineages, including Poaceae, Solanaceae, Fabaceae, and Brassicaceae. However, additional genomic studies are needed to pinpoint the exact phylogenetic placement of the ancient polyploidy events within these lineages and to determine when novel genes resulting from polyploidy have enabled adaptive radiations.