Welcome back! This week we are pleased to welcome our own Paul Martin.

Life in the city:

Opportunities and challenges for interacting species

Urbanization represents an extreme transformation of more natural systems. Populations of most species decline or disappear with urbanization, and yet some species persist and even thrive incities. What determines which species persist or thrive in urban habitats? Direct competitive interactions among species can influence their distributions and resource use, particularly along gradients of environmental challenge. Given the challenges of urbanization, similar interactions may be important for determining which species persist or thrive in cities; however, their role remains poorly understood. In this talk, I will present the results of my collaborative work with Fran Bonier that uses a large, global dataset to test among three alternative hypotheses for how direct competitive interactions and behavioral dominance may influence the breeding occurrence of birds in cities.

We found evidence to support the Competitive Interference Hypothesis: behaviorally dominant species were more widespread in urban habitats than closely-related subordinate species, but only in taxa that thrive in urban environments (hereafter, urban-adapted), and only when dominant and subordinate species overlapped their geographic ranges. This result was evident across diverse phylogenetic groups, but varied significantly with a country’s level of economic development. Urban-adapted, dominant species were more widespread than closely-related subordinate species in cities in developed, but not developing, countries; countries in economic transition showed an intermediate pattern. Our results provide evidence that competitive interactions broadly influence species responses to urbanization, and that these interactions have asymmetric effects on subordinate species that otherwise could be widespread in urban environments. Results further suggest that economic development might accentuate the consequences of competitive interactions, thereby reducing local diversity in cities.

The EEB Seminars run weekly, on Thursdays, in the EEB Lounge of the BioSciences Complex, Room 4338, from 12:30-1:30pm.