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

Ecol Lett. 2009 Jun;12(6):550-60. doi: 10.1111/j.1461-0248.2009.01308.x. Epub 2009 Apr 6.


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 degrees S to 48.2 degrees 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.

MeSH terms

  • Altitude
  • Animals
  • Anura / classification
  • Biodiversity
  • Birds / classification
  • Chiroptera / classification
  • Demography
  • Ecosystem
  • Geography* / statistics & numerical data
  • Lizards / classification
  • Population Density
  • Population Dynamics
  • Rodentia / classification
  • Snakes / classification
  • Temperature
  • Tropical Climate*
  • Urodela / classification
  • Vertebrates* / classification