Narrow thermal tolerance and low dispersal drive higher speciation in tropical mountains

Nicholas R. Polato, Brian A. Gill, Alisha A. Shah, Miranda M. Gray, Kayce L. Casner, Antoine Barthelet, Philipp W. Messer, Mark P. Simmons, Juan M. Guayasamin, Andrea C. Encalada, Boris C. Kondratieff, Alexander S. Flecker, Steven A. Thomas, Cameron K. Ghalambor, N. LeRoy Poff, W. Chris Funk, Kelly R. Zamudio

Research output: Contribution to journalArticlepeer-review

150 Scopus citations


Species richness is greatest in the tropics, and much of this diversity is concentrated in mountains. Janzen proposed that reduced seasonal temperature variation selects for narrower thermal tolerances and limited dispersal along tropical elevation gradients [Janzen DH (1967) Am Nat 101:233–249]. These locally adapted traits should, in turn, promote reproductive isolation and higher speciation rates in tropical mountains compared with temperate ones. Here, we show that tropical and temperate montane stream insects have diverged in thermal tolerance and dispersal capacity, two key traits that are drivers of isolation in montane populations. Tropical species in each of three insect clades have markedly narrower thermal tolerances and lower dispersal than temperate species, resulting in significantly greater population divergence, higher cryptic diversity, higher tropical speciation rates, and greater accumulation of species over time. Our study also indicates that tropical montane species, with narrower thermal tolerance and reduced dispersal ability, will be especially vulnerable to rapid climate change.

Original languageEnglish (US)
Pages (from-to)12471-12476
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number49
StatePublished - Dec 4 2018
Externally publishedYes


  • Climate variability
  • Cryptic diversity
  • Elevation gradient
  • Speciation
  • Thermal tolerance

ASJC Scopus subject areas

  • General


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