Incompatibility and Speciation Within and Between Species
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The process of speciation is integral to producing and maintaining the great biodiversity of life on Earth; yet the underlying mechanisms of reproductive isolation remain largely a mystery. The widely accepted Bateson-Dobzhansky-Muller model cites the accumulation of intrinsic post-zygotic isolating mechanisms as the barrier to reproduction between two species. However, the characteristics of such accumulated incompatibilities are complex and varied and thus challenge our mechanistic understanding of the process of speciation. Using four Caenorhabditis populations, three geographically separate strains of C. remanei, and one strain of closely related C. latens, a multiple cross analysis of parental, F1, and F2 fitness levels was conducted to address these details of speciation, particularly when comparing standing within species incompatibility to incompatibility developed between species. Pairing the analysis of phenotypic measures of fitness and genetic incompatibility with a Mendelian Inheritance model presents compelling evidence of deleterious epistatic interaction in the between species crosses as well as within species crosses. These results indicate that markers of incipient speciation are quantifiably present in otherwise compatible populations of the same species.