Inbreeding and selection response in a small population of honeybee under incomplete reproductive isolation

Speciation occurs when reproductive barriers prevent the exchange of genetic information between individuals. A common form of reproductive barrier between species capable of interbreeding is hybrid sterility. Genomic incompatibilities between the divergent genomes of different species contribute to a reduction in hybrid fitness. These incompatibilities continue to accumulate after speciation, therefore, young divergent taxa with incomplete reproductive isolation are important in understating the genetics leading to speciation. Here, I use two Drosophila subspecies pairs. The first is D. willistoni consisting of D. w. willistoni and D. w. winge. The second subspecies pair is D. pseudoobscura, which is composed of D. p. pseudoobscura and D. p. bogotana. Both subspecies pairs are at the early stages of speciation and show incomplete reproductive isolation through unidirectional hybrid male sterility. In this thesis, I performed an exploratory survey of genome-wide expression analysis using RNA-sequencing on D. willistoni and determined the extent of regulatory divergence between the subspecies using allele-specific expression analysis. I found that misexpressed genes showed a degree of tissue specificity and that the sterile male hybrids had a higher proportion of misexpressed genes in the testes relative to the fertile hybrids. The analysis of regulatory divergence between this subspecies pair found a large (66-70%) proportion of genes with conserved regulatory elements. Of the genes showing evidence or regulatory divergence between subspecies, cis-regulatory divergence was more common than other types. In the D. pseudoobscura subspecies pair, I compared sequence and expression divergence and found no support for directional selection driving gene misexpression in their hybrids. Allele-specific expression analysis revealed that compensatory cis-trans mutations partly explained gene misexpression in the hybrids. The remaining hybrid misexpression occurs due to interacting gene networks or possible co-option of cis-regulatory elements by divergent transacting factors. Overall, the results of this thesis highlight the role of regulatory interactions in a hybrid genome and how these interactions could lead to hybrid breakdown by disrupting gene interaction networks.

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Incomplete Reproductive Isolation in the Blue Mussel (Mytilus edulis and M. trossulus) Hybrid Zone in the Northwest Atlantic: Role of Gamete Interactions and Larval Viability

Biological Bulletin ◽

10.1086/bblv218n3p266 ◽

2010 ◽

Vol 218 (3) ◽

pp. 266-281 ◽

Cited By ~ 14

Author(s):

Marcelo B. B. Miranda ◽

David J. Innes ◽

Raymond J. Thompson

Keyword(s):

Reproductive Isolation ◽

Mytilus Edulis ◽

Hybrid Zone ◽

Blue Mussel ◽

Northwest Atlantic ◽

Gamete Interactions ◽

Incomplete Reproductive Isolation

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Reproductive isolation of hybrid populations driven by genetic incompatibilities

10.1101/007518 ◽

2014 ◽

Author(s):

Molly Schumer ◽

Rongfeng Cui ◽

Gil G Rosenthal ◽

Peter Andolfatto

Keyword(s):

Reproductive Isolation ◽

Alternative Model ◽

Parental Species ◽

Small Population ◽

Hybrid Population ◽

Ecological Niches ◽

Simple Consequence ◽

Hybrid Species ◽

Population Sizes ◽

Adaptive Radiations

Despite its role in homogenizing populations, hybridization has also been proposed as a means to generate new species. The conceptual basis for this idea is that hybridization can result in novel phenotypes through recombination between the parental genomes, allowing a hybrid population to occupy ecological niches unavailable to parental species. A key feature of these models is that these novel phenotypes ecologically isolate hybrid populations from parental populations, precipitating speciation. Here we present an alternative model of the evolution of reproductive isolation in hybrid populations that occurs as a simple consequence of selection against incompatibilities. Unlike previous models, our model does not require small population sizes, the availability of new niches for hybrids or ecological or sexual selection on hybrid traits. We show that reproductive isolation between hybrids and parents evolves frequently and rapidly under this model, even in the presence of ongoing migration with parental species and strong selection against hybrids. Our model predicts that multiple distinct hybrid species can emerge from replicate hybrid populations formed from the same parental species, potentially generating patterns of species diversity and relatedness that mimic adaptive radiations.

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Incomplete reproductive isolation may promote hybrid zone formation between Ligularia tongolensis and L. cymbulifera

10.22541/au.159586597.72114750 ◽

2020 ◽

Author(s):

Rui Yang ◽

Li Hu ◽

Guoqian Yang ◽

Guiling Sun ◽

Xun Gong

Keyword(s):

Reproductive Isolation ◽

Hybrid Zone ◽

Zone Formation ◽

Incomplete Reproductive Isolation

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Taxonomic status of Ceratophysella denticulata (Bagnall, 1941), C. engadinensis (Gisin, 1949) and C. stercoraria Stach, 1963 (Collembola: Hypogastruridae) in the light of laboratory hybridisation studies

Insect Systematics & Evolution ◽

10.1163/187631204788920176 ◽

2004 ◽

Vol 35 (3) ◽

pp. 277-284 ◽

Cited By ~ 1

Author(s):

Dariusz Skarzynski

Keyword(s):

Reproductive Isolation ◽

Taxonomic Status ◽

Introgressive Hybridisation ◽

Springtail Species ◽

Incomplete Reproductive Isolation

AbstractLaboratory hybridisation studies were performed of the springtail species Ceratophysella denticulata, C. engadinensis, C. stercoraria, C. mosquensis, C. impedita and Schaefferia willemi. The studies revealed that the species under consideration are reproductively isolated to different degrees. Rare, unilateral, introgressive hybridisation was detected exclusively between C. denticulata and C. engadinensis. Despite incomplete reproductive isolation these problematic species were recognised as “good” and closely related. The remaining species, including the problematic C. stercoraria, appeared to be completely reproductively isolated and were recognised as “good” and distantly related.

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Incomplete reproductive isolation following host shift in brood parasitic indigobirds

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2008.0733 ◽

2008 ◽

Vol 276 (1655) ◽

pp. 219-228 ◽

Cited By ~ 15

Author(s):

Christopher N Balakrishnan ◽

Kristina M Sefc ◽

Michael D Sorenson

Keyword(s):

Gene Flow ◽

Reproductive Isolation ◽

Host Shift ◽

Plumage Colour ◽

Common Ancestry ◽

Host Races ◽

Host Shifts ◽

Molecular Studies ◽

Close Relatives ◽

Incomplete Reproductive Isolation

Behavioural and molecular studies suggest that brood parasitic indigobirds ( Vidua spp.) rapidly diversified through a process of speciation by host shift. However, behavioural imprinting on host song, the key mechanism promoting speciation in this system, may also lead to hybridization and gene flow among established indigobird species when and if female indigobirds parasitize hosts already associated with other indigobird species. It is therefore not clear to what extent the low level of genetic differentiation among indigobird species is due to recent common ancestry versus ongoing gene flow. We tested for reproductive isolation among three indigobird species in Cameroon, one of which comprises two morphologically indistinguishable host races. Mimicry of host songs corresponded with plumage colour in 184 male indigobirds, suggesting that females rarely parasitize the host of another indigobird species. Paternity analyses, however, suggest that imperfect specificity in host and/or mate choice allows for continuing gene flow between recently formed host races of the Cameroon Indigobird Vidua camerunensis ; while 63 pairs of close relatives were associated with the same host, two strongly supported father–son pairs included males mimicking the songs of the two different hosts of V. camerunensis . Thus, complete reproductive isolation is not necessarily an automatic consequence of host shifts, a result that suggests an important role for natural and/or sexual selection in indigobird speciation.

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