Biology ETDs

Publication Date

Winter 11-14-2019


The distribution of life across the Andes mountains reflects historical elevational-range contraction and expansion. Whereas contraction implies specialization, expansion requires overcoming hidden barriers. Three eco-evolutionary phenomena may drive patterns in rates of elevational range evolution: (1) The Dobzhansky-MacArthur Phenomenon (DMP) predicts lower rates of upward expansion with harsher physical conditions, while downward expansion increases with lower diversity; (2) the evolutionary tendency toward specialization predicts contraction increases when ranges are broad; and (3) natural selection for respiratory performance could suppress expansion across mid-elevations due to gene-environment mismatch. We modeled elevational range shifts of Neotropical landbirds. Contrary to the DMP, upward expansion rates increased with elevation, suggesting higher invasibility of depauperate communities. Downward expansion was constrained at mid-elevations the same elevations where hemoglobin predictably shifts in O2-binding affinity. However, even the relatively fast rates of upward expansion occurred five orders of magnitude slower than those predicted over the next century by escalator models.




macroevolution, evolution, biogeography, macroecology, high altitude adaptation, range evolution

Document Type


Degree Name


Level of Degree


Department Name

UNM Biology Department

First Committee Member (Chair)

Christopher C. Witt

Second Committee Member

Jeffrey C. Long

Third Committee Member

Michael J. Andersen