337. Alix K, Gérard PR, Schwarzacher T, Heslop-Harrison JS. 2017. Polyploidy and interspecific hybridisation: partners for adaptation, speciation and evolution in plants. Annals of Botany 120 https://doi.org/10.1093/aob/mcx079
Polyploidy, defined as whole genome duplication, is present in almost all lineages of higher plants, with multiple rounds of polyploidy occurring in most extant species. This Annals of Botany Special Issue on Polyploidy in Ecology and Evolution presents the evolutionary consequences of new, recent, and ancient polyploidy. Alix et al. survey experimental, genomic, ecological and theoretical studies demonstrating that polyploidization often occurs during periods of major evolutionary transitions and adaptive radiation of species. Polyploidy, the cornerstone of bursts of adaptive speciation, brings about genetic novelty. The emergence of new gene functions enables diversification, speciation, and hence plant evolution.
The figure can be downloaded in PowerPoint format.
Background Polyploidy or whole genome duplication is now recognized as being
present in almost all lineages of higher plants, with multiple rounds of polyploidy
occurring in most extant species. The ancient evolutionary events have been identified through genome sequence analysis, while recent hybridisation events are found in about half of the world’s crops and wild species. Building from this new paradigm for understanding plant evolution, the papers in this Special Issue address questions about polyploidy in ecology, adaptation, reproduction and speciation of wild and cultivated plants from diverse ecosystems. Other papers, including this article, consider genomic aspects of polyploidy.
• Approaches Discovery of the evolutionary consequences of new, evolutionarily
recent, and ancient polyploidy requires a range of approaches. Large scale studies of
both single species, and whole ecosystems, with hundreds to tens of thousands of
individuals, sometimes involving ‘garden’ or transplant experiments are important for studying adaptation. Molecular studies of genomes are needed to measure diversity in genotypes, showing ancestors, the nature and number of polyploidy and backcross events that have occurred, and allowing analysis of gene expression and transposable element activation. Speciation events and the impact of reticulate evolution, require comprehensive phylogenetic analyses and can be assisted by resynthesis of hybrids. In this Special Issue, we include studies ranging in scope from experimental and genomic, through ecological to more theoretical.
• Conclusions The success of polyploidy, displacing the diploid ancestors of almost all
plants, is well illustrated by the huge angiosperm diversity that is assumed to originate from recurrent polyploidisation events. Strikingly, polyploidisation often occurred prior to or simultaneously with major evolutionary transitions and adaptive radiation of species, supporting that concept that polyploidy plays a predominant role in bursts of adaptive speciation. Polyploidy results in immediate genetic redundancy and represents, with the emergence of new gene functions, an important source of novelty. Along with recombination, gene mutation, transposon activity and chromosomal rearrangement, polyploidy and whole genome duplication act as a driver of evolution and divergence in plant behaviour and gene function, enabling diversification, speciation and hence plant evolution.
Key words: Polyploidy, hybrids, ecology, adaptation, evolution, genomics, chromosomes, speciation, whole genome duplication (WGD), crops, weeds, phylogeny, bryophytes,
angiosperms
