Polymorphism of postmating reproductive isolation within plant species

Abstract

Speciation can be viewed as the evolution of reproductive isolation between formerly interbreeding populations. Recent years have seen great advances in our understanding of the genetic mechanisms underlying postmating reproductive isolation during plant speciation. Nevertheless, little is known about the early stages of species divergence and the evolution of reproductive isolation at the within species level. Direct or indirect evidence indicates that intrinsic postzygotic mechanisms are prevalent and often polymorphic among allopatric conspecific populations of plants. We review studies that report direct or indirect evidence for polymorphism of genic (i.e., gene‐based) postmating reproductive isolation within species' ranges. Specifically, we focus on three genic mechanisms often held responsible for reproductive isolation between species: Bateson‐Dobzhansky‐Muller (BDM) incompatibilities and two widespread types of genomic conflict, transmission ratio distortion and cytonuclear interactions. We further highlight the close similarity between reported cases of outbreeding depression among conspecific populations, especially those that correspond to the intrinsic co‐adaptation model, and the origin of genetic incompatibilities. This association holds great promise to help improve our understanding of the processes involved in the initial stage of speciation, and it highlights the close (and often overlooked) relationship between evolutionary and conservation biology.

Admixture increases performance of an invasive plant beyond first‐generation heterosis

“…For example, within C. solstitialis and within C. sulphurea , between‐range outcrossing resulted in a lower seed set than within‐range outcrossing, which suggests that reproductive barriers may have developed between native and invasive populations. Such within‐species reproductive barriers have also been reported in other studies (Hughes & Hollingsworth, ; Scopece, Lexer, Widmer, & Cozzolino, ; Twyford, Kidner, & Ennos, ). However, as we could easily produce seeds of the different experimental crosses in our study, we have no indications that reproductive barriers between the native and invaded ranges have developed yet in M. guttatus .…”

A road map for molecular ecology

“…For example, we already know from mapping studies that polymorphism for isolation traits segregates within populations (Scopece et al . ; Rieseberg & Blackman ; Lindtke et al . ).…”

Ecological divergence plays an important role in strong but complex reproductive isolation in campions (Silene)*

“…The strength of reproductive barriers can vary across population pairs of the diverging lineages, due to both envionmental and genetic causes (Lexer and Widmer ; Scopece et al. ; Larson et al. ); however, variation in reproductive isolation remains poorly explored (e.g., Butlin and Smadja ).…”