Fitness? - Hard to measure evolutionary consequences of individual variation in performance abilities - Use estimates of fitness mating success locomotor performance growth rate survival etc. - Role of genes AND environment - Break research into: 1. Gene to performance 2. Performance outward
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Fitness? - Hard to measure evolutionary consequences of individual variation in performance abilities - Use estimates of fitness mating success locomotor.
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Fitness? - Hard to measure evolutionary consequences of individual variation in performance abilities - Use estimates of fitness
mating success locomotor performance growth rate survival etc.
- Role of genes AND environment
- Break research into: 1. Gene to performance 2. Performance outward
Performance
Physiology Biochemistry Genes?
Fitness
Morphology
Sprint Speed Endurance etc.
Survival and Reproduction
Constraints and Trade-offs ?
These, and their interactions, affect: - activity period - growth rate - locomotor performance - reproductive effort - etc.
- Temperature - Water - Energy
e.g., - lizards are faster when warmer (up to a point)
- dehydrated anurans have lower optimal temperatures
Constraints and Trade-offs ? Pough et al., 2001
Chap. 6
- dehydrated anurans are more prone to fatigue and don’t jump as well
Constraints and Trade-offs ? e.g., Ctenophorus ornatus (an Australian lizard)
growth rate (+) mating success
growth rate (-) surviving dry summergrowth rate (-) ability to regulate salt and
water growth rate (+) survive cold winters
Alternative strategies!
Ctenophorus nuchalis
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
-1 -0.5 0 0.5 1
log Endurance (s)
log
Sp
rin
t S
pee
d (
m/s
)
Sceloporus
Sand
Horned
Crotaphytidae
Agamidae
Teiidae
Lacertidae
Scincidae
Anguidae
Speed and Endurance are positively correlated
23 Species (Adult Males)
Residuals (from regressions
on body mass) Speed and Endurance
do not trade-off
r2 = 0.187 p = 0.039
Speed-Endurance Trade-Offs
Wilson et al. 2002
Xenopus laevis1. Peroneus Muscle 2. Whole Animal
Body Mass
Speed-Endurance Trade-Offs
Wilson et al. 2002
Xenopus laevis
Workloop
Trade-off between speed and endurance at level of individual muscle, but not at level of animals
Feeding in Herps - more time, energy to consume large prey but, cost <1% energy from meal - time minimizers (many small) - movement minimizers (few large) ~ sit and wait ~ active foraging
Pectoral Girdle - tongue and groove joint at coracoid and sternum - allows coracoid to slide relative to sternum
Pough et al. 2001 Figure 8-5
Locomotion
Lepidosaur specializations
- vertebrae - pectoral girdle - hindlimb Hindlimb
- unusual tarsal bones first 4 metatarsals fused special shape of 5th metatarsal (hook or L-shaped) 1st class lever to extend ankle + provide push (like gastroc/ achilles tendon/ heel)
- ankle specializations also
Locomotion
Dynamic bipeds - Support on two legs if in
motionBipedal trends - long hindlimbs - short forelimbs - short presacral vertebral
moves G backwards - relatively long tail
counterbalance - muscles of hindlimb moved proximally
longer tendons speed > force
- elongate plantar tubercle of 5th metatarsal increases in-lever of gastrocnemius -> more
thrust
Locomotion
How increase speed?
Increase stride length - longer limbs (hind) - run up on phalanges (not foot) - alter kinematics of stride
Increase stride frequency - propulsion and retraction - muscle twitch speed
Lateral Undulation - most widely used - horizontal waves down alternating sides of body - generate force at fixed points in environment - body pushes posterolaterally - lateral components cancel
vs. limbed locomotion 1. No fixed points on body for propulsion;
body moved past fixed points in environment 2. No recovery phase (limb retraction) 3. No real vertical component, but combat friction
Pough et al., 2001
Snake Terrestrial Locomotion
Slide Pushing - resembles lateral undulation - but no fixed points in the environment - rapid body waves
to generate some friction on smooth surfaces
Pough et al., 2001
Snake Terrestrial Locomotion
Rectilinear - muscles on both sides of body simultaneously - move in straight line - heavy bodied snakes (boids and vipers)
- 2 sets of costocutaneous muscles from ribs to ventral skin
A. Costocutaneous superior muscles pull skin forward
relative to ribs B. Ventral scales anchored to substrate C. Costocutaneous inferior pulls ribs
(and vertebrae and everything else) forward relative to stationary ventral skin
Fig. 8-15 Pough et al. 2001
rectilinear locomotion
Snake Terrestrial Locomotion
Concertina - slow - high energy - repeated establishment of fixed and
stable contact with substrate
Pough et al., 2001
- used in tunnels - used by arboreal snakes
Snake Terrestrial Locomotion
Sidewinding - low friction or shifting substrates - most snakes capable - forces directed ~vertically
Pough et al., 2001
- sections of body alternately lifted up, moved forward, set down
- snake usually in contact at two points
- can be more efficient than lateral undulation
Snake Terrestrial Locomotion
Saltation ! - small Bitis caudalis (Viperidae) - rapid straightening from anterior to posterior
http://www.plumed-serpent.com/dscour.html
Aquatic Locomotion
Water is dense and viscous
Pough et al., 2001
- support against gravity - resistance for propulsion (e.g., webbed feet) - difficult to move through - requires power drag = resistance of water due to viscosity
- boundary layer - laminar flow vs. turbulence - improved boundary layer retention decreases turbulence and drag
hydrofoil (pressure differential for lift)
Aquatic Locomotion
1. Lateral undulations - each part of body generates force
as well as friction - undulations LARGER as move posteriorly
(opposite on land) ~ increases in surface area
sea snakes, crocodiles, marine iguanas
2. Oscillatory (paired appendages); drag or lift based - Frogs and turtles (no lateral flexion)
simultaneous, webbed Xenopus with special sacral articulation
- Marine turtles “fly” through water generate lift on up and down stroke of
forelimbs hindlimbs for steering
Fossorial Locomotion
- Fossorial anurans generally use hindlimbs to dig
- shorter for increased power - Common in legless groups
- Scolecophidia - Uropeltidae (Alethinophidia) - Amphisbaenians and other Lizards - Caecilians
- specialized skulls robust, shaped to match behavior
- smooth skin - reduced number of scales (if present)
Fossorial Locomotion
- undulatory, concertina, rectilinear
- internal concertina
Pough et al., 2001
Fossorial Locomotion
- sand diving 6 lizard families fringes on toes counter sunk lower jaw labial scales form ‘cutting edge’