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Research
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| Flight has been a significant
underpinning to adaptive radiation in insects, birds, and
bats. Moreover, wing flapping in both insects and volant vertebrates provides
a general problem for biomechanical analysis in that neither maneuverability nor limits to flight performance are well
understood. Equally unclear is the extent to which biomechanical capacity to fly is
actually utilized in nature, either for extant taxa or for possible
evolutionary intermediates. Our approach to these problems
involves a
variety of volant taxa and is two-fold in character: laboratory
investigations of physiological and biomechanical constraints on flight
performance, and fieldwork to elucidate the biomechanics of animal
flight under natural circumstances. The overall goal of this
research
program is to elucidate both evolutionary origins and subsequent
diversification of flight mechanisms, broadly construed.
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Representative Research
1.Biomechanics and evolution of gliding flight in arthropods
Working in
Peru and Panama, I and collaborators Steve Yanoviak and Mike Kaspari
are investigating aerial behaviors and the biomechanical underpinnings
to directed aerial descent in arboreal arthropods. We use a
canopy walkway and climb rainforest trees to obtain a broad diversity
of wingless taxa for study. Documentation of aerial behaviors
in
these groups has important implications for our understanding of the
evolutionary origins of insect flight.
2. Animal flight performance across elevational gradients
Increasing
elevation involves a substantial reduction in both air density and
oxygen partial pressure, which in concert potentially compromise the
ability of animals to fly. In Peru, I and collaborators Jim
McGuire, Chris Witt, and Doug Altshuler are linking hemoglobin sequence
variation to hematological parameters, whole-animal flight energetics,
and hypoxia resistance, using hovering hummingbirds as a model
system. In Sichuan, southwestern China, I and collaborator
Michael Dillon are studying, both inter- and intraspecifically, the
ability of bumblebees to hover across a 4000 meter elevational gradient.
3. Allometry of lift and power production in hovering insects and hummingbirds
The size-dependence of maximum performance in hovering animals remains
quantitatively unresolved. Using a maximal load-lifting
method
of, I and collaborators Doug Altshuler (hummingbirds) and Michael
Dillon (orchid bees) are evaluating interspecific variation in maximum
lifting performance for approximately fifty hummingbird species and
twelve orchid bee species. Prior interspecific comparisons of
animal flight performance have violated statistical assumptions of
independence of data points. We are implementing
phylogenetically
controlled interspecific analyses of maximum lifting performance, and
are linking mechanistically the negative allometry of wingbeat
frequency with geometrical constraints on stroke amplitude to evaluate
changes in hovering capacity with body mass.
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Current research projects |
- Elevational variation in flight mechanics and energetics of the giant hummingbird -
M.Jose Fernandez
- Relative contribution of morphology and behavior to mimicry in ithomiine butterflies -
Ryan Hill
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