Speciation genetics: current status and evolving approaches

Abstract

The view of species as entities subjected to natural selection and amenable to change put forth by Charles Darwin and Alfred Wallace laid the conceptual foundation for understanding speciation. Initially marred by a rudimental understanding of hereditary principles, evolutionists gained appreciation of the mechanistic underpinnings of speciation following the merger of Mendelian genetic principles with Darwinian evolution. Only recently have we entered an era where deciphering the molecular basis of speciation is within reach. Much focus has been devoted to the genetic basis of intrinsic postzygotic isolation in model organisms and several hybrid incompatibility genes have been successfully identified. However, concomitant with the recent technological advancements in genome analysis and a newfound interest in the role of ecology in the differentiation process, speciation genetic research is becoming increasingly open to non-model organisms. This development will expand speciation research beyond the traditional boundaries and unveil the genetic basis of speciation from manifold perspectives and at various stages of the splitting process. This review aims at providing an extensive overview of speciation genetics. Starting from key historical developments and core concepts of speciation genetics, we focus much of our attention on evolving approaches and introduce promising methodological approaches for future research venues.

Histological evidence that diploid hybrids of Cobitis taenia and C. elongatoides (Teleostei, Cobitidae) develop into fertile females and sterile males

“…According to the Dobzhansky-Müller model of hybrid incompatibility in closely related species, some particularly rapidly evolving genes are changing so much that their proteins could make the hybrid offspring sexually incompatible and sterile. Several hybrid incompatibility genes have been successfully identified (Wolf et al, 2010).…”

“…The mechanism and general principles of hybridization, asexuality, polyploidy and speciation are still problematic and well discussed. Polyploidization, chromosomal rearrangements and genomic incompatibilities have been identified as the causes of intrinsic postzygotic isolation of hybrids (Hoffmann & Rieseberg, 2008;Wolf et al, 2010). According to the Dobzhansky-Müller model of hybrid incompatibility in closely related species, some particularly rapidly evolving genes are changing so much that their proteins could make the hybrid offspring sexually incompatible and sterile.…”

The genomics of incompatibility factors and sex determination in hybridizing species of Cottus (Pisces)

“…These result from genetic changes that, while functional in their normal genetic backgrounds, reduce the viability or fertility when recombined in F 1 hybrids. The evolution of intrinsic barriers to reproduction is believed to be a slow process that is outpaced by ecologically driven adaptive evolution (Wolf et al, 2010). However, partial effects, especially those that manifest only in the F 2 generation are expected to evolve more quickly (Edmands, 1999;White et al, 2011).…”

“…In F 2 crosses or later generation hybrids, intrinsic traits can cause selective mortality if essential regulatory interactions are disrupted when ancestral genotypes segregate (Maheshwari and Barbash, 2011). The evolution of such incompatibilities can be explained through different hypothesis related to Haldane's rule (Wolf et al, 2010). Accordingly, the first incompatibilities between young species would manifest in the heterogametic sex.…”

“…In such systems, the nature of barriers to reproduction and genetic factors that affect the fitness of hybrid offspring represent a central aspect to explain evolutionary processes. For example, an important debate relates to the relative importance of intrinsic and extrinsic barriers as species diverge (Wolf et al, 2010) or whenever hybridization occurs (Barton and Gale, 1993;Bierne et al, 2011). Besides the nature of the selective forces, little is known about numbers of incompatibility factors and how they vary between individuals for most species.…”