Biology ETDs

Publication Date

Spring 5-13-2017


Species diversity in mountainous regions is strongly influenced elevational range limits of species, but it is generally not known which abiotic or biotic factors maintain these limits. Using Black-chinned and Broad-tailed Hummingbirds, species with offset but overlapping elevational ranges in the southwestern USA, we investigate the role barometric pressure plays in influencing these limits. In chapter one, we used a hypobaric chamber to test the effects of variable air pressures on interspecific competitive dominance. We sequenced the genes that encode the two adult isoforms of haemoglobin and measured the O2-binding affinity of each isoform. In chapter two, we explored the morphological differences between species and the haematological response of species exposed to variable air pressures. Results suggest that species variation in physiological and behavioral responses to variable air pressures show how biotic and abiotic forces might interact to maintain stable elevational distribution limits, and are potentially resistant to rising temperatures.




hummingbirds, hypobaric hypoxia, high altitude adaptation, elevational replacement

Document Type


Degree Name


Level of Degree


Department Name

UNM Biology Department

First Committee Member (Chair)

Christopher C. Witt

Second Committee Member

Blair O. Wolf

Third Committee Member

Christine M. Mermier

Included in

Biology Commons