author={H. Allen Orr and Michael Turelli},
Hybrid sterility and inviability often result from the accumulation of substitutions that, while functional on their normal genetic backgrounds, cause a loss of fitness when brought together in hybrids. Previous theory has shown that such Dobzhansky-Muller incompatibilities should accumulate at least as fast as the square of the number of substitutions separating two species, the so-called snowball effect. Here we explicitly describe the stochastic accumulation of these incompatibilities as a… 



Dominance, epistasis and the genetics of postzygotic isolation.

A model of two-locus incompatibilities is presented that distinguishes among three types of hybrid interactions: those between heterozygous loci (H(0), those between aheterozygous and a homozygous (or hemizygous) locus (H (1), and those between homozygou loci(H(2)); the relative fitnesses of hybrid genotypes are predicted by calculating the expected numbers of each type of incompatibility.

On the origin of species by sympatric speciation

This work uses multilocus genetics to describe sexual reproduction in an individual-based model and considers the evolution of assortative mating, which leads to reproductive isolation between ecologically diverging subpopulations and conforms well with mounting empirical evidence for the sympatric origin of many species.

The role of hybridization in evolution

Fisher’s model of stabilizing selection on multiple traits, under which reproductive isolation evolves as a side‐effect of adaptation in allopatry, confirms a priori arguments that while recombinant hybrids are less fit on average, some gene combinations may be fitter than the parents, even in the parental environment.

Studies on Hybrid Sterility. II. Localization of Sterility Factors in Drosophila Pseudoobscura Hybrids.

It remains possible that suppression of meiotic pairing may be caused by different mechanisms in different cases, and that sometimes there is no cause and effect relation between the failure of paking and the sterility.

A genetic basis for the inviability of hybrids between sibling species of Drosophila.

A mutation of Drosophila melanogaster whose only known effect is the rescue of otherwise lethal interspecific hybrids has been characterized and is interpreted on the basis of a model for the genetic basis of hybrid inviability of complementary genes.


A positive correlation between degree of divergence (measured as Nei's genetic distance, D) and degree of postzygotic isolation is found and in anurans, hybrid sterility appears to evolve more quickly than inviability, which is consistent with the conclusions that involved Drosophila species.

Correspondence between sexual isolation and allozyme differentiation: a test in the salamander Desmognathus ochrophaeus.

Ethological reproductive isolation and genetic divergence across 26 protein loci were measured among populations of the salamander Desmognathus ochrophaeus in the southern Appalachian Mountains, but genetic distance is a poor predictor of ethological isolation in these salamanders.

Divergence in proteins, mitochondrial DNA, and reproductive compatibility across the isthmus of Panama.

Measurements of biochemical and reproductive divergence for seven closely related, transisthmian pairs of snapping shrimps indicate, however, that isolation was staggered rather than simultaneous, and the four least divergent pairs provide the best estimate for rates of molecular divergence and speciation.

Natural selection and parallel speciation in sympatric sticklebacks.

The post-Pleistocene radiation of threespine sticklebacks was used to infer natural selection in the origin of species, and speciation has proceeded in this adaptive radiation in a repeatable fashion.

The genome sequence of Drosophila melanogaster.

The nucleotide sequence of nearly all of the approximately 120-megabase euchromatic portion of the Drosophila genome is determined using a whole-genome shotgun sequencing strategy supported by extensive clone-based sequence and a high-quality bacterial artificial chromosome physical map.