The polyploidy revolution then…and now: Stebbins revisited

Abstract

Polyploidy has long been considered a major force in plant evolution. G. Ledyard Stebbins, Jr., an architect of the Modern Synthesis, elegantly addressed a broad range of topics, from genes to chromosomes to deep phylogeny, but some of his most lasting insights came in the study of polyploidy. Here, we review the immense impact of his work on polyploidy over more than 60 years, from his entrance into this fledgling field in the 1920s until the end of his career. Stebbins and his contemporaries developed a model of polyploid evolution that persisted for nearly half a century. As new perspectives emerged in the 1980s and new genetic tools for addressing key aspects of polyploidy have become available, a new paradigm of polyploidy has replaced much of the Stebbinsian framework. We review that paradigm shift and emphasize those areas in which the ideas of Stebbins continue to propel the field forward, as well as those areas in which the field was held back; we also note new directions that plant geneticists and evolutionists are now exploring in polyploidy research. Perhaps the most important conclusion from recent and ongoing studies of polyploidy is that, following Levin and others, polyploidy may propel a population into a new adaptive sphere given the myriad changes that accompany genome doubling.

The genome sequence of the orchid Phalaenopsis equestris

“…More specifically, the WGD event was dated at 75.57 million years ago, with lower and upper 90% confidence interval limits of 71.50 and 80.73 million years ago, respectively (Supplementary Note). As the common ancestor of the crown group of orchids is supposed to have lived during the Late Cretaceous period sometime between 76 and 84 million years ago 13 , this finding would suggest that the orchid-specific WGD event occurred in association with the origin of this clade, and polyploidy is indeed proposed as a frequent mechanism of speciation in angiosperms 31,32 . In contrast, many members of the Orchidaceae family underwent drastic rate shifts (transition and transversion) during their evolutionary history due to periods of accelerated molecular evolution caused by their short life cycles and altered life history strategies [33][34][35] .…”

Chromosome numbers of selected species of Elatine L. (Elatinaceae)

“…It is believed, that polyploidization is a major driving force of plant evolution [36,37]. Obtained chromosome number data clearly indicate that polyploidization was one of the most important phenomena accompanying the evolution of the genus Elatine.…”

Hybridization in Plants: Old Ideas, New Techniques

“…This can be due to greater gene regulatory flexibility as a result of homologspecific gene regulation (Dong and Adams, 2011;Combes et al, 2012) or alternative splicing (Zhou et al, 2011) in response to environmental perturbation. However, there remains a need for more empirical evidence demonstrating ecological differentiation facilitated by allopolyploidy (Abbott et al, 2013;Madlung, 2013;Soltis et al, 2014).…”