phenomenon
biogeographic variation
Morphological differences in the same species across different geographic regions
hypothesis
Dobzhansky-MacArthur hypothesis
Predicts that a species' high-elevation range limit is determined by harsh abiotic conditions whereas its low-elevation range limit is set by antagonistic species interactions
theory
faunal elements
Biogeographic classification of species based on their broader distributional affinities and evolutionary origins
measurement
area of occupancy
The area within a species' extent of occurrence that is actually occupied by the species, calculated using grid-based methods