Testing for intrinsic and extrinsic barriers between climate-correlated mitolineages in a natural avian hybrid zone: a mitonuclear perspective

Animals rely on cooperation between two genomes—the mitochondrial and the nuclear—to produce energy. When populations with different versions of these genomes interbreed, the mismatch can sometimes reduce survival or reproduction. I studied this process in the eastern yellow robin, a widespread Australian bird with two mitochondrial types linked to climate. Using nest monitoring, survival data, and population models, I tested whether these genomic differences affect fitness. Surprisingly, I found little evidence of harm from mismatched combinations. Instead, environment and location mattered more. These results challenge simple predictions and inform conservation in a changing climate.