Abstract
Speciation is often driven by pre-mating isolation barriers that prevent interspecific mating. Although these isolation barriers can evolve rapidly in natural populations, these barriers are often incomplete, leading to interspecific hybrids. Despite the importance for our fundamental understanding of speciation, the specific mechanisms that regulate the formation of interspecific hybrids remain poorlyunderstood in many systems, especially in speciose mite taxa. In our lab, we study several features of the mating behaviour and hybridization patterns of three Tetranychus spider mite species. No-choice genetic crosses using a wide panel of near-isogenic lines revealed varying and asymmetrical degrees of hybridization. Using the same mite lines, behavioural assays uncovered strong intraspecific variation in mate attraction in one of the focal Tetranychus species. By long-term acclimation to different host plants, we tested whether this attraction covaries with fitness. Quantifying the strength and direction of pre-mating isolation among our three hybridizing species uncovered complex patterns of non-assortative,assortative, and disassortative mating behaviour. We further observed that intraspecific variation in mate attraction is a major genetic determinant regulating interspecific mating. To test whether disassortative mating evolved by reproductive interference, we included an allopatric Tetranychus species in ourbehavioural assays. Together, our findings contribute to a broader understanding of how behavioral mechanisms can shape hybridization.