Gabriel Munar-Delgado, Paula Hidalgo-Rodríguez, Gregorio Sánchez-Montes, Jaime Potti, José Luis Tella, Wolfgang Forstmeier, Pim Edelaar

Adaptive divergence has long been a core topic in the field of evolutionary biology, with natural selection traditionally considered its only driver. Here we focus on the ability of matching habitat choice to generate population divergence and reproductive isolation. This alternative mechanism of divergence considers that individuals choose their habitats based on an evaluation of the ecological match between their phenotype and the available environments, which subsequently limits gene flow. To test this, we conducted experiments with captive zebra fiches equipped with transponder-tags and using transponder-operated bird feeders. We thereby created within a single aviary two areas with distinct resources, and the associated ecological traits that provided access to only one of the resources. We found that most zebra finches chose to breed in the same area as where they had access to their ecological resource, thereby creating population divergence in the absence of current natural selection on the ecological trait. This choice of breeding area indirectly resulted in assortative mating for the ecological trait. If the ecological trait were heritable, this assortative mating would carry the obtained divergence into the next generation. Our results experimentally confirm the predicted ability of matching habitat choice to drive rapid population divergence and limit maladaptive gene flow, especially at the small temporal and spatial scales where natural selection is unlikely to do so (here: one generation and one aviary). This might be increasingly relevant in a world where anthropogenic impacts create rapid environmental changes.