How important is plasticity versus evolutionary divergence for habitat partitioning in nature? In a recently published paper, Queen’s Biology Associate Professors Fran Bonier and Paul Martin, and former Queen’s Biology MSc student Kevin Burke use a global dataset on urban birds to provide one of the few tests of the relative importance of plasticity versus evolutionary divergence underlying habitat partitioning. They find evidence for both. Greater habitat partitioning was associated with increased range overlap among dominant and subordinate species – a factor that is expected to increase the intensity of selection favoring evolutionary divergence. For birds that thrive in cities, however, the greatest impact on habitat partitioning appears to result from subordinates actively shifting out of cities when dominant species occur there, consistent with plasticity in response to aggressive, dominant species.
The study results suggest distinct ways to mitigate loss of biodiversity caused by urbanization. When dominant species thrive in cities, providing resources for subordinates that cannot be monopolized by the dominant (e.g., nest boxes with entrance holes too small for the dominant species to use) would help subordinates to persist. In the case of evolutionary divergence, adding distinct habitat refuges suited to subordinate species could help them colonize or persist in cities.
