Table 2.

Potential mechanisms of genetic incompatibilities in respect to the rules of speciation in species bearing homomorphic sex chromosomes like amphibians (Haldane's rule: asymmetry of hybrid fitness; large sex chromosome effect: reduced introgression at sex-linked compared to autosomal loci). Other mechanisms may include autosomal–autosomal interactions or cyto-nuclear interactions.

			large sex chromosome effect
			yes	no
XY system	Haldane's rule	yes	faster male/faster heterogametic sex/meiotic drive	faster male (autosomal)
		no	other	other
ZW system	Haldane's rule	yes	faster heterogametic sex/meiotic drive	other
		no	potentially faster male (sex-linked)	potentially faster male (autosomal)