Intraspecific Class Research Articles

LOCOMOTOR COMPENSATION CREATES A MISMATCH BETWEEN LABORATORY AND FIELD ESTIMATES OF ESCAPE SPEED IN LIZARDS: A CAUTIONARY TALE FOR PERFORMANCE-TO-FITNESS STUDIES

A key assumption in evolutionary studies of locomotor adaptation is that standard laboratory measures of performance accurately reflect what animals do under natural circumstances. One widely examined measure of performance is maximum sprint speed, which is believed to be important for eluding predators, capturing prey, and defending territories. Previous studies linking maximum sprint speed to fitness have focused on laboratory measurements, and we suggest that such analyses may be appropriate for some species and intraspecific classes, but not others. We provide evidence for a general inverse relationship between maximum laboratory sprint speed and the percentage of maximum capacity that animals use when escaping from a threat in the field (the model of locomotor compensation). Further, absolute values of field escape speed and maximum laboratory speed are not significantly related when comparing across a diverse group of Anolis and lacertid lizards. We show that this pattern of locomotor compensation holds both within (i.e., among intraspecific classes) and among lizard species (with some exceptions). We propose a simple method of plotting field escape speed (y-axis) versus maximum laboratory speed (x-axis) among species and/or intraspecific classes that allows researchers to determine whether their study organisms are good candidates for relating laboratory performance to fitness. We suggest that species that reside directly on, or near the "best fitness line" (field escape speed = maximum laboratory speed) are most likely to bear fruit for such studies.

LOCOMOTOR COMPENSATION CREATES A MISMATCH BETWEEN LABORATORY AND FIELD ESTIMATES OF ESCAPE SPEED IN LIZARDS: A CAUTIONARY TALE FOR PERFORMANCE-TO-FITNESS STUDIES

A key assumption in evolutionary studies of locomotor adaptation is that standard laboratory measures of performance accurately reflect what animals do under natural circumstances. One widely examined measure of performance is maximum sprint speed, which is believed to be important for eluding predators, capturing prey, and defending territories. Previous studies linking maximum sprint speed to fitness have focused on laboratory measurements, and we suggest that such analyses may be appropriate for some species and intraspecific classes, but not others. We provide evidence for a general inverse relationship between maximum laboratory sprint speed and the percentage of maximum capacity that animals use when escaping from a threat in the field (the model of locomotor compensation). Further, absolute values of field escape speed and maximum laboratory speed are not significantly related when comparing across a diverse group of Anolis and lacertid lizards. We show that this pattern of locomotor compensation holds both within (i.e., among intraspecific classes) and among lizard species (with some exceptions). We propose a simple method of plotting field escape speed (y-axis) versus maximum laboratory speed (x-axis) among species and/ or intraspecific classes that allows researchers to determine whether their study organisms are good candidates for relating laboratory performance to fitness. We suggest that species that reside directly on, or near the “best fitness line” (field escape speed = maximum laboratory speed) are most likely to bear fruit for such studies.

An intraspecific analysis of trade-offs in sprinting performance in a West Indian lizard species (Anolis lineatopus)

We examined whether a trade-off exists in sprinting ability among individuals within the Caribbean lizardAnolis lineatopus. Specifically, we made the following predictions: Longer-legged (relative to body size) individual lizards should sprint faster than shorter-legged lizards on a broad (5.1 cm diameter) rod. However, longer-legged lizards should also decline in sprinting performance to a greater extent than shorter-legged lizards when sprinting on rods of different diameters. To test these predictions, we examined morphology and sprinting performance in adult male, adult female and juvenileA. lineatopus. As predicted, longer-legged lizards are faster sprinters than shorter-legged lizards on the broad substrate, but they also decline more in speed between the broad and narrow (0.7 cm diameter) dowel. However, despite statistically significant morphological differences among intraspecific classes, differences in morphology did not result in differences in sprinting performance among intraspecific classes, with the exception that larger lizards run faster than smaller lizards on each dowel size.

An intraspecific analysis of trade-offs in sprinting performance in a West Indian lizard species (Anolis lineatopus)

We examined whether a trade-off exists in sprinting ability among individuals within the Caribbean lizardAnolis lineatopus. Specifically, we made the following predictions: Longer-legged (relative to body size) individual lizards should sprint faster than shorter-legged lizards on a broad (5.1 cm diameter) rod. However, longer-legged lizards should also decline in sprinting performance to a greater extent than shorter-legged lizards when sprinting on rods of different diameters. To test these predictions, we examined morphology and sprinting performance in adult male, adult female and juvenileA. lineatopus. As predicted, longer-legged lizards are faster sprinters than shorter-legged lizards on the broad substrate, but they also decline more in speed between the broad and narrow (0.7 cm diameter) dowel. However, despite statistically significant morphological differences among intraspecific classes, differences in morphology did not result in differences in sprinting performance among intraspecific classes, with the exception that larger lizards run faster than smaller lizards on each dowel size.

Structural Habitat and Time Budget of a Tropical Anolis Lizard

Structural habitat data generally support the interpretation that competition for food results in habitat partitioning. In this investigation, the importance of ethological factors in determining the structural habitat of Anolis lizards is demonstrated by examining the structural habitat of Anolis polylepis during foraging and social interaction, its two major activities. “Overall” structural habitats show that intraspecific classes use perches of significantly different heights and diameters. Perch heights of adult males and females are also shown to be related to the type of activity in which they are engaged. Overall structural habitat data show a greater difference between the sexes than actually exists in their feeding locations. Ecological differences between insular and continental Anolis potentially affecting the structural habitat are also discussed.