Paper 26 - by Tanner Hawkins

Geographic ranges of North American terrestrial mammals

Christy McCain is an Associate Professor at the University of Colorado Boulder. Her research interests are in “to improve our understanding of the patterns and underlying mechanisms of diversity, abundance, and distributions of organisms in a search for general theories of biodiversity.”

Sydney Anderson is the Curator Emeritus of Mammalogy at the American Museum of Natural History.

Rapoport's Rule, the idea that species’ geographic ranges increase with distance from the equator, is contentious in biogeography. One source of contention is how researchers choose to define ranges, as measuring these effects while trying to separate out other phenomena such as the mid-domain effect can be difficult. Depending on how the analysis is done, biogeographers and ecologists can come to very different and opposing conclusions.

For an example, compare this paper with the Stevens paper (paper 40). Unlike Stevens, Anderson tested mammals by order, rather than looking at the broader taxonomic groups that Stevens did. But although there is a difference in scale, Anderson came to the opposite conclusion. Whereas Stevens found support for Rapoport’s Rule in all vertebrate taxa aside from birds, Anderson found no support for any mammalian taxa besides bats.

Why did they come to opposite conclusions? It could be due to a difference in (a) methods, (b) analysis, or (c) available data. Unfortunately, I don’t really have the background to say which aspects are significant, so I’d like to frame my questions around this:

●       Are there large disciplinary differences between ecology and biogeography that may contribute to how these studies are done?

●      How have methods over time changed that may contribute?