Quantifying Patterns in the Evolution of Reproductive Isolation

Mendelson, Tamra C.; Inouye, Brian D.; Rausher, Mark D.

doi:10.1111/j.0014-3820.2004.tb01724.x

Cited by 34 publications

(6 citation statements)

References 33 publications

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“…As for sexual species, we found all range of incompatibility barriers between auto-pseudogamous Mesorhabditis species. Similar to previous work performed on reproductive isolation in sexual species [ 24 – 26 ], our results suggest a relationship between the genetic distance between species and the isolation mechanism (see Table 1 ). Indeed, the incompatibility mechanism between the distant species M. belari and M. monhystera is pre-copulatory, at least acting prior to sperm transfer.…”

Section: Discussionsupporting

confidence: 91%

Diversification and hybrid incompatibility in auto-pseudogamous species of Mesorhabditis nematodes

et al. 2020

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Background: Pseudogamy is a reproductive system in which females rely on the sperm of males to activate their oocytes, generally parasitizing males of other species, but do not use the sperm DNA. The nematode Mesorhabditis belari uses a specific form of pseudogamy, where females produce their own males as a source of sperm. Males develop from rare eggs with true fertilization, while females arise by gynogenesis. Males thus do not contribute their genome to the female offspring. Here, we explored the diversity of reproductive mode within the Mesorhabditis genus and addressed species barriers in pseudogamous species. Results: To this end, we established a collection of over 60 Mesorhabditis strains from soil and rotting vegetal matter. We found that males from pseudogamous species displayed a reduced size of their body, male tail and sperm cells compared to males of sexual Mesorhabditis species, as expected for males that face little competition. Using rDNA sequences and crosses, we could define 11 auto-pseudogamous biological species, with closely related species pairs and a possible single origin of pseudogamy in the Mesorhabditis genus. Most crosses between males and females of different species did not even produce female progeny. This surprising species barrier in pseudogamous egg activation was pre or postcopulatory depending on the species pair. In the latter case, when hybrid embryos were produced, most arrested before the first embryonic cell division. Hybrid incompatibility between auto-pseudogamous species was due to defective interaction between sperm and oocyte as well as defective reconstitution of zygotic centrosomes. Conclusions: We established a collection of sexual and pseudo-sexual species which offer an ideal framework to explore the origin and consequences of transition to asexuality. Our results demonstrate that speciation occurs in the pseudogamous state. Whereas genomic conflicts are responsible for hybrid incompatibility in sexual species, we here reveal that centrosomes constitute key organelles in the establishment of species barrier.

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Section: Discussionsupporting

confidence: 91%

Diversification and hybrid incompatibility in auto-pseudogamous species of Mesorhabditis nematodes

et al. 2020

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“…Genetic distances of ≈0.1 are often associated with a substantial, or even complete, reproductive isolation ( Mendelson et al 2004 ; Elliot and Crespi 2006 ). However, the two parents used in our study produced viable, phenotypically normal offspring, despite having 0.14 of their nucleotides different.…”

Section: Discussionmentioning

confidence: 99%

Crossing-Over in a Hypervariable Species Preferentially Occurs in Regions of High Local Similarity

Seplyarskiy

Logacheva

Penin

et al. 2014

Molecular Biology and Evolution

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Recombination between double-stranded DNA molecules is a key genetic process which occurs in a wide variety of organisms. Usually, crossing-over (CO) occurs during meiosis between genotypes with 98.0–99.9% sequence identity, because within-population nucleotide diversity only rarely exceeds 2%. However, some species are hypervariable and it is unclear how CO can occur between genotypes with less than 90% sequence identity. Here, we study CO in Schizophyllum commune, a hypervariable cosmopolitan basidiomycete mushroom, a frequently encountered decayer of woody substrates. We crossed two haploid individuals, from the United States and from Russia, and obtained genome sequences for their 17 offspring. The average genetic distance between the parents was 14%, making it possible to study CO at very high resolution. We found reduced levels of linkage disequilibrium between loci flanking the CO sites indicating that they are mostly confined to hotspots of recombination. Furthermore, CO events preferentially occurred in regions under stronger negative selection, in particular within exons that showed reduced levels of nucleotide diversity. Apparently, in hypervariable species CO must avoid regions of higher divergence between the recombining genomes due to limitations imposed by the mismatch repair system, with regions under strong negative selection providing the opportunity for recombination. These patterns are opposite to those observed in a number of less variable species indicating that population genomics of hypervariable species may reveal novel biological phenomena.

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“…Toads, a species-rich group of anurans, are particularly germane to this goal given the apparent discrepancies regarding patterns of reproductive isolation [1], [20], [48]–[50] and the diversity of sex determination systems found in frogs and toads (reviewed in [51]). …”

Section: Discussionmentioning

confidence: 99%

Patterns of Reproductive Isolation in Toads

2008

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Understanding the general features of speciation is an important goal in evolutionary biology, and despite significant progress, several unresolved questions remain. We analyzed an extensive comparative dataset consisting of more than 1900 crosses between 92 species of toads to infer patterns of reproductive isolation. This unique dataset provides an opportunity to examine the strength of reproductive isolation, the development and sex ratios of hybrid offspring, patterns of fertility and infertility, and polyploidization in hybrids all in the context of genetic divergence between parental species. We found that the strength of intrinsic postzygotic isolation increases with genetic divergence, but relatively high levels of divergence are necessary before reproductive isolation is complete in toads. Fertilization rates were not correlated to genetic divergence, but hatching success, the number of larvae produced, and the percentage of tadpoles reaching metamorphosis were all inversely related with genetic divergence. Hybrids between species with lower levels of divergence developed to metamorphosis, while hybrids with higher levels of divergence stopped developing in gastrula and larval stages. Sex ratios of hybrid offspring were biased towards males in 70% of crosses and biased towards females in 30% of crosses. Hybrid females from crosses between closely related species were completely fertile, while approximately half (53%) of hybrid males were sterile, with sterility predicted by genetic divergence. The degree of abnormal ploidy in hybrids was positively related to genetic divergence between parental species, but surprisingly, polyploidization had no effect on patterns of asymmetrical inviability. We discuss explanations for these patterns, including the role of Haldane's rule in toads and anurans in general, and suggest mechanisms generating patterns of reproductive isolation in anurans.

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Quantifying Patterns in the Evolution of Reproductive Isolation

Cited by 34 publications

References 33 publications

Diversification and hybrid incompatibility in auto-pseudogamous species of Mesorhabditis nematodes

Diversification and hybrid incompatibility in auto-pseudogamous species of Mesorhabditis nematodes

Crossing-Over in a Hypervariable Species Preferentially Occurs in Regions of High Local Similarity

Patterns of Reproductive Isolation in Toads

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