Gene Expression Differences in Hybrids at Beginning of Speciation Continuum

Abstract

The formation of new species results from reproductive isolation, or the barrier to successful mating between organisms of divergent populations. The degree of reproductive isolation can be measured by the reduction in fitness of hybrid offspring that can result from incompatibilities between the genotypes of each parent. In this study, genetic incompatibilities arising at the earliest stage of speciation are examined between intraspecific hybrids in which an effectively sterile hybrid phenotype termed “still” is observed at ~50% frequency in crosses between divergent populations of Tribolium castaneum. Timing and magnitude of gene expression regulation is examined at four stages of development, two pupal and two adult. Gene interactions are examined on a systemic level to elucidate proximal mechanisms for misregulation such as allele bias and alternative splicing. Further evidence is put forth for phosphine resistance as a possible driver of the genetic incompatibility behind “still.” Misregulated genes exhibit functional enrichment across developmental timepoints for oxidative damage, neuromuscular function, and chromosome structure.