Sex-biased dispersal drives Mito-Nuclear Discordance in simulated populations

Reconstructing the evolutionary dynamics of natural populations requires an understanding of the geographical distribution of nuclear and mitochondrial genetic diversity. The analysis of these two genetic markers often reveals discordant patterns (mito-nuclear discordance) that can arise simply as a consequence of their different effective population sizes (Ne). Species-specific sex-biased dispersal may also contribute to the mito-nuclear discordance observed in natural populations. However, the relative contribution of genetic drift versus sex-biased dispersal in driving mito-nuclear discordance remains insufficiently evaluated. Here, we use forward genetic simulations to address this knowledge gap. Our findings support the baseline level of mito-nuclear discordance arising from different Ne, but show that this discordance is magnified by sex-biased dispersal. We demonstrate that female-biased dispersal leads to a marked spatial mismatch between mitochondrial and nuclear diversity across the simulated populations, thereby reducing the spatial concordance between the two markers. Conversely, our simulations indicate that even pronounced male-biased dispersal produces only minor effects on the concordance in the spatial distribution of the mitochondrial and nuclear markers. Our results suggest that mito-nuclear discordance may be particularly frequent in taxa in which female-biased dispersal is predominant, like birds, and underscore the importance of integrating nuclear and mitochondrial genomes, as well as the impact of sex-biased dispersal, for accurately interpreting patterns of genetic diversity and reconstructing evolutionary histories.