Get access
Advertisement

Vertebrate range sizes indicate that mountains may be ‘higher’ in the tropics

Authors

  • Christy M. McCain

    Corresponding author
      *Correspondence and present address: CU Museum of Natural History, MCOL 265 UCB, University of Colorado, Boulder, CO 80309-0265, USA. E-mail: christy.mccain@colorado.edu
    Search for more papers by this author

*Correspondence and present address: CU Museum of Natural History, MCOL 265 UCB, University of Colorado, Boulder, CO 80309-0265, USA. E-mail: christy.mccain@colorado.edu

Abstract

In 1967, Daniel Janzen proposed the influential, but largely untested hypothesis, that tropical mountain passes are physiologically higher than temperate mountains. I test his key prediction, the one upon which all the others rely: namely, that elevational range sizes of organisms get larger on mountains at increasing latitudes. My analyses use 170 montane gradients spanning 36.5° S to 48.2° N latitude compiled from over 80 years of research and 16 500 species of rodents, bats, birds, lizards, snakes, salamanders, and frogs. In support of Janzen’s prediction, I find that elevational range size increases with increasing latitude for all vertebrate groups except rodents. I document additional lines of evidence for temperature variability as a plausible mechanism for trends in vertebrate range size, including strong effects of thermoregulation and daily temperature variability, and a weak effect of precipitation.

Get access to the full text of this article

Ancillary