Manipulating Testosterone to Assess Links between Behavior, Morphology, and Performance in the Brown Anole Anolis sagrei

2015

How well an organism completes an ecologically relevant task -its performance -is often considered a key factor in determining individual fitness. Historically, ecomorphological studies have examined how morphological traits determine individual performance in a static manner, assuming that differential fitness in a population is due indirectly to differences in morphological traits that determine a simple measure of performance. This assumption, however, ignores many ecological factors that can constrain performance in nature, such as substrate variation and individual behavior. We examined some of these complexities in the morphology-performance-fitness paradigm, primarily the impact that substrate variation has on performance. We measured maximal sprint speed of green anole lizards on four substrates that varied in size and complexity and are used by or available to individuals in nature. Performance decreased significantly from a broad substrate to a narrow substrate, and lizards were three times slower on a complex substrate than the broadest substrate. We also detected trade-offs in running on substrates with different diameters and in cluttered versus uncluttered environments. Furthermore, morphological predictors of performance varied among substrates. This indicates that natural selection may act on different morphological traits, depending on which substrates are used by individuals, as well as an individual's ability to cope with changes in substrate rather than maximal capacities.

Section: Methodsmentioning

confidence: 99%

“…Lizards were inspected visually for health before and after each trial. The fastest time over a 25 cm interval on each substrate was considered the maximal speed on that substrate for each lizard (Cox et al, 2009). The lizards were encouraged to run by pursuing them with a hand or a paintbrush.…”

Section: Methodsmentioning

confidence: 99%

Sprint sensitivity and locomotor trade-offs in green anole (Anolis carolinensis) lizards

Sathe

2015

“…We measured mass and snout-vent length (SVL) of each lizard, as well as endurance capacity on a motorized treadmill (PetRun model PR700 modified for lower speeds). Endurance was recorded as the time to exhaustion, determined by when lizards lost their righting response while running on a treadmill rotating at 0.3 km h −1 (Perry et al, 2004;Cox et al, 2009;Husak et al, 2015Husak et al, , 2016. Treadmills were cleaned with ethanol between lizards during measurements and training bouts described below.…”

Section: Pre-treatment Measurementsmentioning

confidence: 99%

Exercise training reveals trade-offs among endurance performance and immune function, but not growth, in juvenile lizards

Roy

Lovern

2017

Acquired energetic resources allocated to a particular trait cannot then be re-allocated to a different trait. This often results in a trade-off between survival and reproduction for the adults of many species, but such a trade-off may be manifested differently in juveniles not yet capable of reproduction. Whereas adults may allocate resources to current and/or future reproduction, juveniles can only allocate to future reproduction. Thus, juveniles should allocate resources toward traits that increase survival and their chances of future reproductive success. We manipulated allocation of resources to performance, via endurance exercise training, to examine trade-offs among endurance capacity, immune function and growth in juvenile green anole lizards. We trained male and female captive anoles on a treadmill for 8 weeks, with increasing intensity, and compared traits with those of untrained individuals. Our results show that training enhanced endurance capacity equally in both sexes, but immune function was suppressed only in females. Training had no effect on growth, but males had higher growth rates than females. Previous work showed that trained adults have enhanced growth, so juvenile growth is either insensitive to stimulation with exercise, or they are already growing at maximal rates. Our results add to a growing body of literature indicating that locomotor performance is an important part of life-history trade-offs that are sex and age specific.

“…This is a highly repeatable, standard procedure for Anolis lizards Foster and Higham, 2012). We measured endurance by running lizards to exhaustion (loss of righting reflex) on a motorised treadmill (PetRun model PR700 modified for lower speeds) rotating at 0.3 km h −1 (Perry et al, 2004;Cox et al, 2009). Lizards were placed on the moving treadmill and encouraged to run by gentle tapping of the tail and hindlimbs with a small fan paintbrush.…”

Section: Pre-treatment Measurementsmentioning

confidence: 99%

Making Olympic lizards: the effects of specialised exercise training on performance

Keith

Wittry

2015

Exercise training is well known to affect a suite of physiological and performance traits in mammals, but effects of training in other vertebrate tetrapod groups have been inconsistent. We examined performance and physiological differences among green anole lizards (Anolis carolinensis) that were trained for sprinting or endurance, using an increasingly rigorous training regimen over 8 weeks. Lizards trained for endurance had significantly higher posttraining endurance capacity compared with the other treatment groups, but groups did not show post-training differences in sprint speed. Although acclimation to the laboratory environment and training explain some of our results, mechanistic explanations for these results correspond with the observed performance differences. After training, endurance-trained lizards had higher haematocrit and larger fast glycolytic muscle fibres. Despite no detectable change in maximal performance of sprint-trained lizards, we detected that they had significantly larger slow oxidative muscle fibre areas compared with the other treatments. Treatment groups did not differ in the proportion of number of fibre types, nor in the mass of most limb muscles or the heart. Our results offer some caveats for investigators conducting training research on non-model organisms and they reveal that muscle plasticity in response to training may be widespread phylogenetically.