OVERVIEW. I am interested in attempting to understand the evolution
of complex systems that involve a combination of behavior, physiology and
morphology. I believe that using a comparative, functional and experimental
approach combined with an ecological perspective provides the rigor necessary
for studying evolutionary adaptation. Snakes have been one convenient group
for me to address this question because specialized function has resulted
in convergent evolution of behavior and morphology among several lineages
within snakes. However, I am also studying a wider variety of vertebrate
taxa to achieve the long term goal of a very general understanding of the
evolutionary interrelationships between behavior and morphology in complex
systems such as those involved in locomotion. Snakes. A large portion of my previous work has dealt with
the proximate functional consequences of morphological variability and
the extent of behavioral plasticity for snake locomotion. For example,
the comparative anatomy of axial skeleton and muscles in snakes reveals
some clear patterns of morphological variability that are associated with
behaviorally specialized modes of locomotion. I developed quantitative
methods to clarify the kinematics of these locomotor behaviors and
to compare performance among different locomotor behaviors and species.
I have used electromyography to determine the muscular mechanisms
of different locomotor behaviors within a single species as well comparing
neural control of the same locomotor behavior between species with different
anatomy.
Past research with Al
Bennett (University of California, Irvine) combined laboratory testing
of locomotor performance (speed and endurance) with a mark and recapture
study of a wild population of garter snakes to correlate directly locomotor
capacity with survivorship. I hope to combine future field studies with
additional laboratory observations to clarify even further the relative
importance of speed and locomotor behavior both within and among different
species of vertebrates.
Collaborative work with Harold Voris (Field
Museum of Natural History, Chicago) has examined the feeding behavior
and natural history of marine snakes in southeast Asia. Secondary invasion
of the marine habitat has occurred independently in at least four different
lineages of snakes which can all be found at a single site in Malaysia.
Hence, we have attempted to clarify how this diversity at a single site
is accommodated by differences in microhabitat and diet.
Presently, I am focusing primarily on the performance and and axial motor
patterns involved in the arboreal locomotion of snakes. In addition to the
challenges of maintaining balance and preventing slipping on cylindrical
surfaces of varying diameter and incline (Astley & Jayne, 2007;
video), snakes
in arboreal environments often must cross gaps, which can also be a very
challenging task (Jayne & Riley, 2007;
video). The combination of the structural
variation in arboreal habitats and the phylogenetic diversity of snakes that
have become arboreal specialists creates a rich diversity of environmental,
anatomical and behavioral diversity and be studied to gain fundamental insight
into some of the ecologically relevant consequences of variation in
musculoskeletal design.
Fish. In collaborative work with George
Lauder at University of California, Irvine, I have studied the kinematics
and neuromuscular control of the swimming in two species of fish (largemouth
bass and bluegill sunfish) belonging to a well-defined monophyletic group.
Besides clarifying the role of peripheral morphology on motor output, carefully
examining the changes associated with of locomotor speed has provided
considerable insights into fiber type recruitment of muscle.
Lizards.
Past research with my post-doc Duncan
J. Irschick involved the limbed locomotion of lizards. Generalized
species of lizards have "sprawling" limb posture that differs considerably
from the better-studied upright limb postures of bird and mammals. However,
lizard taxa such as chameleons and geckos have limb postures that depart
considerably from the generalized condition for lizards. Thus, we can examine
the extent to which evolutionary specializations in anatomy may have involved
concomitant changes in neural control. Besides interspecific variation
in limb function, individual lizards commonly have considerable behavioral
variation for moving: 1) over a wide range of speeds, 2) quadrupedally
and bipedally
, 3) uphill and downhill. Thus, we investigated motor pattern, movement
and performance for these diverse behaviors
in order to determine the extent to which these behaviors differ fundamentally
and have consequences for whole animal performance.
Although lizards have often served as a model
organisms for studying locomotor performance, the functional basis of differences
in performance has barely been examined for these animals. Consequently, our
data have clarified some of the causal factors
that may underlie conspicuous differences in locomotor capacity.
RESEARCH
INTERESTS
