Data from: Gametic selection, developmental trajectories, and extrinsic heterogeneity in Haldane's rule

Deciphering the genetic and developmental causes of the disproportionate
rarity, inviability and sterility of hybrid males, Haldane's rule, is
important for understanding the evolution of reproductive isolation
between species. Moreover, extrinsic and pre-zygotic factors can
contribute to the magnitude of intrinsic isolation experienced between
species with partial reproductive compatibility. Here we use the nematodes
Caenorhabditis briggsae and C. nigoni to quantify the sensitivity of
hybrid male viability to extrinsic temperature and developmental timing,
and test for a role of mito-nuclear incompatibility as a genetic cause. We
demonstrate that hybrid male inviability manifests almost entirely as
embryonic, not larval, arrest and is maximal at the lowest rearing
temperatures, indicating an intrinsic-by-extrinsic interaction to hybrid
inviability. Crosses using mitochondrial substitution strains that have
reciprocally introgressed mitochondrial and nuclear genomes show that
mito-nuclear incompatibility is not a dominant contributor to post-zygotic
isolation and does not drive Haldane's rule in this system. Crosses
also reveal that competitive superiority of X-bearing sperm provides a
novel means by which post-mating pre-zygotic factors exacerbate the rarity
of hybrid males. These findings highlight the important roles of gametic,
developmental, and extrinsic factors in modulating the manifestation of
Haldane's rule.