Hybridization in Plants: Old Ideas, New Techniques

Abstract

Hybridization has played an important role in the evolution of many lineages. With the growing availability of genomic tools and advancements in genomic analyses, it is becoming increasingly clear that gene flow between divergent taxa can generate new phenotypic diversity, allow for adaptation to novel environments, and contribute to speciation. Hybridization can have immediate phenotypic consequences through the expression of hybrid vigor. On longer evolutionary time scales, hybridization can lead to local adaption through the introgression of novel alleles and transgressive segregation and, in some cases, result in the formation of new hybrid species. Studying both the abundance and the evolutionary consequences of hybridization has deep historical roots in plant biology. Many of the hypotheses concerning how and why hybridization contributes to biological diversity currently being investigated were first proposed tens and even hundreds of years ago. In this Update, we discuss how new advancements in genomic and genetic tools are revolutionizing our ability to document the occurrence of and investigate the outcomes of hybridization in plants.

Correlated evolution of self and interspecific incompatibility across the range of a Texas wildflower

“…The cost, or in some cases benefit, to hybridization between species generates selection to increase or decrease II. Fertilization by interspecific pollen often results in seed abortion, reduced hybrid survival and hybrid sterility (Lowry et al ., ; Baack et al ., ) and yet, hybridization between some taxa generates exceptionally fit or fecund offspring through heterosis (Lippman & Zamir, ; Goulet et al ., ).…”

Adaptive introgression and maintenance of a trispecies hybrid complex in range‐edge populations of Populus

“…Plant genomes seem to be especially tolerant of hybridization (Rieseberg, ; Soltis & Soltis, ; Suarez‐Gonzalez, Lexer, & Cronk, ; Whitney, Ahern, Campbell, Albert, & King, ), and the increase in trait variability can translate into community‐level consequences for plant–herbivore or plant–microbe associations (Evans, Allan, & Whitham, ; Floate, Godbout, Lau, Isabel, & Whitham, ; Lamit et al., ). Selection may also act on this increased variance to drive introgression of genomic regions between parental species, opening up physiological niches unavailable to either parental species and permitting expansion into new habitats by increasing niche breadth or stress tolerance (Goulet, Roda, & Hopkins, ; Rieseberg et al., ; Whitney et al., ).…”

“…The ecological, genetic and genomic factors underlying the diverse outcomes in Populus hybrid zones are poorly understood, but some insights on selection and adaptive introgression can be gained by characterizing these zones with genomewide molecular markers (Goulet et al., ; Suarez‐Gonzalez, Lexer et al., ). For example, in Europe, population genomic analyses of replicate hybrid zones between P. alba and P. tremula have shown strong postzygotic isolation due to genetic incompatibilities between species, but that isolation was not strong enough to prevent introgression driven by selection (Lexer et al., ; Lindtke, Gompert, Lexer, & Buerkle, ).…”

Independent homoploid hybrid speciation events in the Macaronesian endemic genusArgyranthemum

“…Homoploid hybrid speciation (HHS), the origin of a new species by hybridization without a change in chromosome number, is generally considered to be exceptionally rare in angiosperm evolution (Goulet, Roda, & Hopkins, ; Hegarty & Hiscock, ; Schumer, Rosenthal, & Andolfatto, ; Soltis & Soltis, ) with a recent review identifying 28 putative examples of HHS in flowering plants (Kadereit, ). This is in sharp contrast to polyploid hybrid speciation, involving a doubling of chromosome number, which is thought to account for approximately 15% of angiosperm speciation events (Wood et al., ).…”