Does elevational range-size (ERR) slope inform the idea that
mountain passes are higher in the tropics?
Long-term stability of environmental conditions, inferred via adjacency
to the equator as well as location along an elevational gradient,
facilitates not only ecological niche specialization but also determines
relative shifts in average range-sizes. Our results support the idea
that “mountain passes are higher in the tropics” as indicated by
differences in ERR slopes for species-rich families with greater
affiliation to lowland tropical of Sundaland, as compared to places with
either contemporary, or historic, variability of conditions, such as for
flora noted with either montane or Sahul affiliation.