Topography-driven isolation, speciation and a global increase of endemism with elevation
Author
Steinbauer, Manuel J.; Field, Richard; Grytnes, John-Arvid; Trigas, Panayiotis; Ah-Peng, Claudine; Attorre, Fabio; Birks, H. John B.; Borges, Paulo A. V.; Cardoso, Pedro; Chou, Chang-Hung; De Sanctis, Michele; Sequeira, Miguel M. de; Duarte, Maria C.; Elias, Rui B.; Fernández-Palacios, José María![ULL authority ULL authority](/xmlui/themes/Mirage2/images/autoridades/autoridad.png)
Date
2016Abstract
Aim Higher-elevation areas on islands and continental mountains tend
to be separated by longer distances, predicting higher endemism at
higher elevations; our study is the first to test the generality of the
predicted pattern. We also compare it empirically with contrasting
expectations from hypotheses invoking higher speciation with area,
temperature and species richness.
Location Thirty-two insular and 18 continental elevational gradients
from around the world.
Methods We compiled entire floras with elevation-specific occurrence
information, and calculated the proportion of native species that are
endemic (‘percent endemism’) in 100-m bands, for each of the 50
elevational gradients. Using generalized linear models, we tested the
relationships between percent endemism and elevation, isolation,
temperature, area and species richness.
Results Percent endemism consistently increased monotonically with
elevation, globally. This was independent of richness–elevation
relationships, which had varying shapes but decreased with elevation at
high elevations. The endemism–elevation relationships were consistent
with isolation-related predictions, but inconsistent with hypotheses
related to area, richness and temperature.
Main conclusions Higher per-species speciation rates caused by
increasing isolation with elevation are the most plausible and
parsimonious explanation for the globally consistent pattern of higher
endemism at higher elevations that we identify. We suggest that
topography-driven isolation increases speciation rates in mountainous
areas, across all elevations and increasingly towards the equator. If so, it
represents a mechanism that may contribute to generating latitudinal diversity gradients in a way that is consistent with both present-day and
palaeontological evidence