Interlocus gene conversion causes mosaic divergence in tandem paralogues - simulating HMA4 evolution in Arabidopsis halleri

Following gene duplication, the evolutionary trajectories of gene copies can be shaped by various processes including mutation, selection, recombination and interlocus gene conversion (IGC). To explore their dynamics and consequences, we developed a mathematical model that simulates the early evolution of recently duplicated, tandemly arrayed gene families with positive selection on the new gene copy. We compared the results of our model to sequence variation of the three tandemly arrayed HEAVY METAL ATPase 4 (HMA4) gene copies of Arabidopsis halleri, which are known to undergo IGC. However, rate and efficacy of IGC vary within genes, resulting in a mosaic pattern of divergence. Informed by empirical data, our model captures the impact of IGC and unequal crossing-over on the diversity within each gene copy and the divergence among them. By tailoring the model to the HMA4 gene copies, we demonstrate the models flexibility and its potential to provide insights into the evolutionary dynamics driving the evolution of tandemly arrayed paralogues. This study enhances our understanding of the balance between homogenization and divergence of gene family evolution.