OOS 18-1 - Avian morphoscapes: A framework for characterizing the drivers of intraspecific trait variation in North American birds

Intraspecific trait variation represents an important, but often ignored, component of biodiversity. This variation has implications for how organisms interact with their environment and for ecological interactions among species within communities. Substantial gaps in our understanding currently exist, however, regarding how and why traits vary over species’ ranges. Characterizing this variation has the potential to inform decisions regarding how we characterize ecologically distinct populations, which has substantial consequences for environmental management efforts, and to ultimately elucidate the eco-evolutionary dynamics that shape these organisms. Given the large spatial extents over which intraspecific variation must be explored, effectively addressing these questions is a challenging task, requiring a substantial volume of data.

Here we leverage large-scale morphological trait data collected as part of a continental-scale bird capture program, the Monitoring Avian Productivity and Survivorship program, using hierarchical spatial Gaussian Process models. Using this approach, we characterize morphological landscapes, morphoscapes, for dozens of bird species across North America. Our traits of interest for this study are mass and wing length, though there exists opportunity to integrate information a number of traits into the future. Here we show how this principled statistical approach provides an opportunity to explore how morphology varies as the composition of species in these avian communities changes over space (characterized using data from eBird, a large-scale community science platform) and to what degree this is mediated by abiotic factors, including temperature and air density. We demonstrate where the rate of morphological change over space is highest across species’ ranges, illustrate the degree to which these changes are gradual versus discrete, and show how these patterns varies among species. We further compare the magnitude of morphological variation across multiple levels of biological organization, from populations to communities, illustrating that differences within species can be as large as differences among species, for certain traits. This study demonstrates how this morphoscape framework can facilitate our understanding of intraspecific morphological variation, a key component of biodiversity, and what this can tell us about the interactions between organisms and both the abiotic and biotic environments.