Transgressive phenotypes and evidence of weak postzygotic isolation in F1 hybrids between closely related capuchino seedeaters

Campagna, Leonardo; Mazzulla, José Carlos

doi:10.1371/journal.pone.0199113

Cited by 14 publications

(18 citation statements)

References 30 publications

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“…Sexual selection would also be consistent with our observations suggesting that many loci have experienced sweeps in parallel in different species. We note that there is now strong evidence-including genetic, behavioral, coloration, song and captive breeding data [66][67][68][69] -that these are truly distinct species, not artificial taxonomic constructs based on superficial morphological features.…”

Section: Discussionmentioning

confidence: 87%

Genomic islands of differentiation in a rapid avian radiation have been driven by recent selective sweeps

Hejase

Salman‐Minkov

Campagna

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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Numerous studies of emerging species have identified genomic “islands” of elevated differentiation against a background of relative homogeneity. The causes of these islands remain unclear, however, with some signs pointing toward “speciation genes” that locally restrict gene flow and others suggesting selective sweeps that have occurred within nascent species after speciation. Here, we examine this question through the lens of genome sequence data for five species of southern capuchino seedeaters, finch-like birds from South America that have undergone a species radiation during the last ∼50,000 generations. By applying newly developed statistical methods for ancestral recombination graph inference and machine-learning methods for the prediction of selective sweeps, we show that previously identified islands of differentiation in these birds appear to be generally associated with relatively recent, species-specific selective sweeps, most of which are predicted to be soft sweeps acting on standing genetic variation. Many of these sweeps coincide with genes associated with melanin-based variation in plumage, suggesting a prominent role for sexual selection. At the same time, a few loci also exhibit indications of possible selection against gene flow. These observations shed light on the complex manner in which natural selection shapes genome sequences during speciation.

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Section: Discussionmentioning

confidence: 87%

Genomic islands of differentiation in a rapid avian radiation have been driven by recent selective sweeps

Hejase

Salman‐Minkov

Campagna

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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“…These can range from mild to severe, but the simulation results show that only a small reduction in hybrid fitness has a powerful effect in limiting the blending of two species. Sexual and social selection may be especially prone to lead to hybrids having characteristics that are not simply a blending of the two species but rather are surprising and outside the range of variation in the parental forms (i.e., "transgressive" traits; Rieseberg et al 1999;Dittrich-Reed and Fitzpatrick 2013;Campagna et al 2018). Finally, the simulations demonstrate that assortative mating itself can result in a form of selection against intermediate hybrids, due to rare-type disadvantage (e.g., Bridle et al 2006).…”

Section: Discussionmentioning

confidence: 99%

Assortative mating in hybrid zones is remarkably ineffective in promoting speciation

Irwin

2019

Preprint

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Running title: "Assortative mating and hybrid zone width" Data Accessibility: Upon acceptance for publication in a peer-reviewed journal, data and code will be deposited in the Dryad Digital Repository. AbstractAssortative mating and other forms of partial prezygotic isolation are often viewed as being more important than partial postzygotic isolation (low fitness of hybrids) early in the process of speciation. Here we simulate secondary contact between two populations ('species') to examine effects of pre-and postzygotic isolation in preventing blending. A small reduction in hybrid fitness (e.g., 10%) produces a narrower hybrid zone than a strong but imperfect mating preference (e.g., 10x stronger preference for conspecific over heterospecific mates). This is because, in the latter case, rare F1 hybrids find each other attractive (due to assortative mating), leading to the gradual buildup of a full continuum of intermediates between the two species. The cline is narrower than would result from purely neutral diffusion over the same number of generations, but this effect is due to the frequency-dependent mating disadvantage of individuals of rare mating types. Hybrids tend to pay this cost of rarity more than pure individuals, meaning there is an induced postzygotic isolation effect of assortative mating.When this induced mating disadvantage is removed, partial assortative mating does not prevent eventual blending of the species. These results prompt a questioning of the concept of partial prezygotic isolation, since it is not very isolating unless there is also postzygotic isolation.

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“…These can range from mild to severe, but the simulation results show that only a small reduction in hybrid fitness has a powerful effect in limiting the blending of two species. Sexual and social selection may be especially prone to lead to hybrids having characteristics that are not simply a blending of the two species but rather are surprising and outside the range of variation in the parental forms (i.e., "transgressive" traits; Rieseberg et al 1999;Dittrich-Reed and Fitzpatrick 2013;Campagna et al 2018). Finally, assortative mating itself can result in a form of selection against intermediate hybrids, due to rare-type disadvantage (e.g., Bridle et al 2006).…”

Section: Cline Width (Functional Loci)mentioning

confidence: 99%

Assortative Mating in Hybrid Zones Is Remarkably Ineffective in Promoting Speciation

Irwin

2020

The American Naturalist

118

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Assortative mating and other forms of partial prezygotic isolation are often viewed as being more important than partial postzygotic isolation (low fitness of hybrids) early in the process of speciation. Here I simulate secondary contact between two populations ('species') to examine effects of pre-and postzygotic isolation in preventing blending. A small reduction in hybrid fitness (e.g., 10%) produces a narrower hybrid zone than a strong but imperfect mating preference (e.g., 10x stronger preference for conspecific over heterospecific mates). This is because, in the latter case, rare F1 hybrids find each other attractive (due to assortative . CC-BY-NC-ND 4.

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Transgressive phenotypes and evidence of weak postzygotic isolation in F1 hybrids between closely related capuchino seedeaters

Cited by 14 publications

References 30 publications

Genomic islands of differentiation in a rapid avian radiation have been driven by recent selective sweeps

Genomic islands of differentiation in a rapid avian radiation have been driven by recent selective sweeps

Assortative mating in hybrid zones is remarkably ineffective in promoting speciation

Assortative Mating in Hybrid Zones Is Remarkably Ineffective in Promoting Speciation

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