- Email: [email protected]
4.5. Behavioral performance in anuran amphibians: Relationships with fitness
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Abstracts / Comparative Biochemistry and Physiology, Part A 148 (2007) S17–S23
food consumption, which indicates that selection on these traits would result in a correlated evolution of BMR. However, BMR was not genetically correlated with ability cope with restricted access to water, male dominance, or litter mass. In the second part of the project, we have launched a multi-directional artificial selection experiment, with 16 lines of the voles (and at least 15 reproducing families per line): 4 selected for ability to cope with herbivorous diet (H), 4 selected for exercise-induced aerobic capacity (A), 4 selected for intensity of predatory behavior towards crickets (P), and 4 unselected (C; control). After three generations of the selection, we observed significant direct response to the selection for all the traits. During the 4day trial with herbivorous diet, young voles from H lines lost less body mass (mean ± S.D.) compared to controls (H: − 1.9 g; C: − 2.6 g; p = 0.008). The aerobic capacity was higher in the A lines than in C lines (A: 4.2 ± 0.55; C: 3.6 ± 0.50 ml O2/min; p b 0.001). In P lines, 42% individuals showed predatory behavior whereas in C lines only 24% (p = 0.045). In subsequent generations, we will test for correlated response in BMR and other traits, and eventually will be able to identify genetic bases of the variation at the molecular level. The three directions of the selection in our experiment correspond to major directions of adaptive strategies of terrestrial vertebrates. Therefore, more generally, the experiment can be treated as a laboratory model of adaptive radiation, and will become a unique tool for testing hypotheses concerning evolution of complex adaptations. doi:10.1016/j.cbpa.2007.06.041
4.3. Trade-offs in muscle and behavioural performance within and among individuals James, R.S. Biomolecular and Sport Sciences, Coventry University, UK [email protected] Skeletal muscle can perform many different tasks during animal behaviour acting to rapidly produce high power output (e.g. during sprinting), to produce power efficiently over long periods of time (e.g. during endurance locomotion), to produce force isometrically to stabilise a limb (e.g. during amplexus or the stance phase of locomotion) or to absorb power to act as a brake. However, the mechanical properties of muscles are determined by their composition, that in turn reflects trade-offs between the differing tasks performed by the muscle and the relative amount of time spent performing each task. Inter-individual analyses of whole-muscle performance have demonstrated trade-offs between maximum power output and fatigue resistance in isolated muscles, such that some individuals were found to have a gastrocnemius muscle that produced relatively high power output, but had relatively low fatigue resistance and vice versa (James et al., 2007). These trade-offs at the muscular level may translate themselves into trade-offs at the organismal level with some individuals excelling at explosive tasks such as sprinting or jumping but being poor at endurance based tasks. However, trade-
offs in locomotory performance have been more difficult to demonstrate, probably due in part to effects related to the ‘better athlete’ hypothesis. Since muscular design trade-offs appear to affect ecologically relevant performance traits they are likely under strong natural selection and adapt to reflect the ecology and natural history of the species. James RS, Navas CA and Herrel A (2007) J. Exp. Biol. 210, 923–933. doi:10.1016/j.cbpa.2007.06.042
4.4. Clawing your way to the top: Variation, repeatability, and social benefits of chela strength in slender crayfish Angilletta Jr., M.J., Bywater, C.L., and Wilson, R.S. Ecology & Organismal Biology, Indiana State University, USA [email protected] Animals commonly signal their strength to conspecifics during disputes over resources or mates. In crayfish, such threats involve the chela (or claw), which is capable inflicting considerable damage to an opponent. Surprisingly, chela size is a poor indicator of chela strength, commonly leading to situations where crayfish signal dishonestly. We found that the strength of crayfish was highly repeatable between days and between temperatures, indicating that dishonest signaling is a reliable phenomenon. We then asked whether male crayfish use information about their relative strength (i.e., the residual of chela strength regressed on chelae size) when interacting with other males. A simple optimality model was developed to predict whether a crayfish would run from an opponent of a given claw size. Our model made predictions under three scenarios: (1) crayfish use information about their own strength relative to their opponent's expected strength, (2) crayfish use information about their own strength relative to their opponent's actual strength, and (3) crayfish use no information about strength. Staged encounters between focal individuals and random opponents provided support for the third scenario: crayfish seem unaware of their own relative strength and are unable to gauge the actual strength of their opponents. Dishonesty provides clear social benefits to slender crayfish, but the costs that maintain this unusual system of signaling remain unknown. doi:10.1016/j.cbpa.2007.06.043
4.5. Behavioral performance in anuran amphibians: Relationships with fitness Bevier, C.R. Biology, Colby College, USA [email protected] The advertisement call of male frogs is a familiar secondary sexual characteristic that has been well studied on several
Abstracts / Comparative Biochemistry and Physiology, Part A 148 (2007) S17–S23
levels. Among species, variation in nightly or seasonal patterns of calling activity, such as species that breed for prolonged or continuous periods and those that breed more opportunistically, provides opportunities to study different reproductive strategies and the relationship of calling behavior to overall patterns of energy use. Individual males of a species exhibit variation in call characteristics that influence male competition and female choice. This variation is largely driven by physiological capacity to produce energetically expensive calls. Female preferences are often based on dynamic properties of the male's call, and females of many species have been shown to prefer acoustic traits that are more energetically expensive. Ultimately such individual variation should influence male reproductive success but only a few investigations have demonstrated beneficial effects, such as greater hatching success or tadpole survival, in offspring of males that produce calls with characteristics preferred by females. I will present an overview of the physiological and biochemical correlates of calling behavior, and discuss how variation in these traits affects male fitness in anuran amphibians. doi:10.1016/j.cbpa.2007.06.044
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correlations with life histories of whole animal energy metabolism. Our results suggest that physiological traits of animals are traits with a complex genetic architecture, with additive genetic components in some cases, maternal– nonadditive variance in others, interacting with morphological and life history traits through genetic covariances. These results suggest a high evolutionary potential to the physiological phenotype, and the resulting optima will depend on the form of the adaptive landscape in the population at a given time. doi:10.1016/j.cbpa.2007.06.045
4.P1. Genetic correlation between metabolic rate and food consumption in the bank vole: Consequence for evolution of endothermy Sadowska, E.T., Stanisz, A., Baliga-Klimczyk, K., Labocha, M.K., and Koteja, P. Jagiellonian University, Poland [email protected]
4.6. Heritability of physiological traits: The case of metabolic rate Nespolo, R.F. Instituto de Ecología y Evolución, Facultad de Ciencias, Universidad Austral de Chile. Casilla 567, Valdivia, Chile [email protected] Evolutionary physiology is an emerging discipline with roots in comparative physiology. One major change in the emergence of this discipline was an explicit new focus on viewing organisms as the evolutionary products of natural selection. The shift in research emphasis from comparative physiology to evolutionary physiology has resulted in physiological traits becoming important elements in broad research programs of evolution and ecology. Evolutionary quantitative genetics is a theory-based biological discipline that has developed the quantitative tools to test explicit evolutionary hypotheses. The role of quantitative genetics has been paramount, in studying the microevolution of morphology, behavior and life history, but not physiology. As a consequence, little basic information is known such as additive genetic variation of physiological traits and the magnitude of genetically based trade-offs (i.e., genetic correlations) with other traits. With these motivations in mind, we have developed a research program aimed to decompose the sources of phenotypic variation in animals. Some of our research goals have been to assess (1) the inter-individual variation, (2) amount of additive genetic variance and (3) the genetic
The main focus of our experiment is on the question concerning the sources of interspecific variation in basal metabolic rate (BMR) and mechanisms behind evolution of endothermy in mammals. We have already reported that in the bank vole, Myodes (=Clethrionomys) glareolus, mass-independent BMR is positively genetically correlated with the aerobic capacity achieved in an exercise test (ACswim) but not during cold exposure (ACcold). Here, we test the hypothesis that total energy budget, measured as food consumption, is positively genetically correlated with BMR and ACswim but not with ACcold. The experiment was performed on about 750 males (mean ± S.D.; body mass = 21.2 ± 2.9 g; age = 103 ± 30 days) from six generations bred in laboratory. BMR was measured at thermally neutral temperature in fasted animals. The aerobic capacity was measured in two ways, to distinguish between locomotor performance (swimming) and thermogenic capacity (cold exposure). Food consumption was measured in a 4-day trial. Values of food consumption (4.3 ± 0.7 g/day), BMR (52.5 ± 6.0 ml O2/h), ACswim (257.2 ± 30.5 ml O2/h) and ACcold (270.5 ± 37.3 ml O2/h) varied remarkably among individuals. Food consumption increased with body mass of individuals (r = 0.53, p b 0.001) and with body mass gain during the trail (r = 0.31, p b 0.001). Narrow-sense heritability of mass-independent food consumption (corrected also for body mass changes) was 0.19 (p b 0.001). There is a positive additive genetic correlation between the food consumption and BMR (rA = 0.46) and ACswim (rA = 0.49), and there is no evidence for the genetic correlation between food consumption and ACcold. The results are consistent with a hypothesis that high BMR and endothermy in mammals evolved in connection with evolution of locomotor capabilities and high overall daily
Abstracts / Comparative Biochemistry and Physiology, Part A 148 (2007) S17–S23
food consumption, which indicates that selection on these traits would result in a correlated evolution of BMR. However, BMR was not genetically correlated with ability cope with restricted access to water, male dominance, or litter mass. In the second part of the project, we have launched a multi-directional artificial selection experiment, with 16 lines of the voles (and at least 15 reproducing families per line): 4 selected for ability to cope with herbivorous diet (H), 4 selected for exercise-induced aerobic capacity (A), 4 selected for intensity of predatory behavior towards crickets (P), and 4 unselected (C; control). After three generations of the selection, we observed significant direct response to the selection for all the traits. During the 4day trial with herbivorous diet, young voles from H lines lost less body mass (mean ± S.D.) compared to controls (H: − 1.9 g; C: − 2.6 g; p = 0.008). The aerobic capacity was higher in the A lines than in C lines (A: 4.2 ± 0.55; C: 3.6 ± 0.50 ml O2/min; p b 0.001). In P lines, 42% individuals showed predatory behavior whereas in C lines only 24% (p = 0.045). In subsequent generations, we will test for correlated response in BMR and other traits, and eventually will be able to identify genetic bases of the variation at the molecular level. The three directions of the selection in our experiment correspond to major directions of adaptive strategies of terrestrial vertebrates. Therefore, more generally, the experiment can be treated as a laboratory model of adaptive radiation, and will become a unique tool for testing hypotheses concerning evolution of complex adaptations. doi:10.1016/j.cbpa.2007.06.041
4.3. Trade-offs in muscle and behavioural performance within and among individuals James, R.S. Biomolecular and Sport Sciences, Coventry University, UK [email protected] Skeletal muscle can perform many different tasks during animal behaviour acting to rapidly produce high power output (e.g. during sprinting), to produce power efficiently over long periods of time (e.g. during endurance locomotion), to produce force isometrically to stabilise a limb (e.g. during amplexus or the stance phase of locomotion) or to absorb power to act as a brake. However, the mechanical properties of muscles are determined by their composition, that in turn reflects trade-offs between the differing tasks performed by the muscle and the relative amount of time spent performing each task. Inter-individual analyses of whole-muscle performance have demonstrated trade-offs between maximum power output and fatigue resistance in isolated muscles, such that some individuals were found to have a gastrocnemius muscle that produced relatively high power output, but had relatively low fatigue resistance and vice versa (James et al., 2007). These trade-offs at the muscular level may translate themselves into trade-offs at the organismal level with some individuals excelling at explosive tasks such as sprinting or jumping but being poor at endurance based tasks. However, trade-
offs in locomotory performance have been more difficult to demonstrate, probably due in part to effects related to the ‘better athlete’ hypothesis. Since muscular design trade-offs appear to affect ecologically relevant performance traits they are likely under strong natural selection and adapt to reflect the ecology and natural history of the species. James RS, Navas CA and Herrel A (2007) J. Exp. Biol. 210, 923–933. doi:10.1016/j.cbpa.2007.06.042
4.4. Clawing your way to the top: Variation, repeatability, and social benefits of chela strength in slender crayfish Angilletta Jr., M.J., Bywater, C.L., and Wilson, R.S. Ecology & Organismal Biology, Indiana State University, USA [email protected] Animals commonly signal their strength to conspecifics during disputes over resources or mates. In crayfish, such threats involve the chela (or claw), which is capable inflicting considerable damage to an opponent. Surprisingly, chela size is a poor indicator of chela strength, commonly leading to situations where crayfish signal dishonestly. We found that the strength of crayfish was highly repeatable between days and between temperatures, indicating that dishonest signaling is a reliable phenomenon. We then asked whether male crayfish use information about their relative strength (i.e., the residual of chela strength regressed on chelae size) when interacting with other males. A simple optimality model was developed to predict whether a crayfish would run from an opponent of a given claw size. Our model made predictions under three scenarios: (1) crayfish use information about their own strength relative to their opponent's expected strength, (2) crayfish use information about their own strength relative to their opponent's actual strength, and (3) crayfish use no information about strength. Staged encounters between focal individuals and random opponents provided support for the third scenario: crayfish seem unaware of their own relative strength and are unable to gauge the actual strength of their opponents. Dishonesty provides clear social benefits to slender crayfish, but the costs that maintain this unusual system of signaling remain unknown. doi:10.1016/j.cbpa.2007.06.043
4.5. Behavioral performance in anuran amphibians: Relationships with fitness Bevier, C.R. Biology, Colby College, USA [email protected] The advertisement call of male frogs is a familiar secondary sexual characteristic that has been well studied on several
Abstracts / Comparative Biochemistry and Physiology, Part A 148 (2007) S17–S23
levels. Among species, variation in nightly or seasonal patterns of calling activity, such as species that breed for prolonged or continuous periods and those that breed more opportunistically, provides opportunities to study different reproductive strategies and the relationship of calling behavior to overall patterns of energy use. Individual males of a species exhibit variation in call characteristics that influence male competition and female choice. This variation is largely driven by physiological capacity to produce energetically expensive calls. Female preferences are often based on dynamic properties of the male's call, and females of many species have been shown to prefer acoustic traits that are more energetically expensive. Ultimately such individual variation should influence male reproductive success but only a few investigations have demonstrated beneficial effects, such as greater hatching success or tadpole survival, in offspring of males that produce calls with characteristics preferred by females. I will present an overview of the physiological and biochemical correlates of calling behavior, and discuss how variation in these traits affects male fitness in anuran amphibians. doi:10.1016/j.cbpa.2007.06.044
S19
correlations with life histories of whole animal energy metabolism. Our results suggest that physiological traits of animals are traits with a complex genetic architecture, with additive genetic components in some cases, maternal– nonadditive variance in others, interacting with morphological and life history traits through genetic covariances. These results suggest a high evolutionary potential to the physiological phenotype, and the resulting optima will depend on the form of the adaptive landscape in the population at a given time. doi:10.1016/j.cbpa.2007.06.045
4.P1. Genetic correlation between metabolic rate and food consumption in the bank vole: Consequence for evolution of endothermy Sadowska, E.T., Stanisz, A., Baliga-Klimczyk, K., Labocha, M.K., and Koteja, P. Jagiellonian University, Poland [email protected]
4.6. Heritability of physiological traits: The case of metabolic rate Nespolo, R.F. Instituto de Ecología y Evolución, Facultad de Ciencias, Universidad Austral de Chile. Casilla 567, Valdivia, Chile [email protected] Evolutionary physiology is an emerging discipline with roots in comparative physiology. One major change in the emergence of this discipline was an explicit new focus on viewing organisms as the evolutionary products of natural selection. The shift in research emphasis from comparative physiology to evolutionary physiology has resulted in physiological traits becoming important elements in broad research programs of evolution and ecology. Evolutionary quantitative genetics is a theory-based biological discipline that has developed the quantitative tools to test explicit evolutionary hypotheses. The role of quantitative genetics has been paramount, in studying the microevolution of morphology, behavior and life history, but not physiology. As a consequence, little basic information is known such as additive genetic variation of physiological traits and the magnitude of genetically based trade-offs (i.e., genetic correlations) with other traits. With these motivations in mind, we have developed a research program aimed to decompose the sources of phenotypic variation in animals. Some of our research goals have been to assess (1) the inter-individual variation, (2) amount of additive genetic variance and (3) the genetic
The main focus of our experiment is on the question concerning the sources of interspecific variation in basal metabolic rate (BMR) and mechanisms behind evolution of endothermy in mammals. We have already reported that in the bank vole, Myodes (=Clethrionomys) glareolus, mass-independent BMR is positively genetically correlated with the aerobic capacity achieved in an exercise test (ACswim) but not during cold exposure (ACcold). Here, we test the hypothesis that total energy budget, measured as food consumption, is positively genetically correlated with BMR and ACswim but not with ACcold. The experiment was performed on about 750 males (mean ± S.D.; body mass = 21.2 ± 2.9 g; age = 103 ± 30 days) from six generations bred in laboratory. BMR was measured at thermally neutral temperature in fasted animals. The aerobic capacity was measured in two ways, to distinguish between locomotor performance (swimming) and thermogenic capacity (cold exposure). Food consumption was measured in a 4-day trial. Values of food consumption (4.3 ± 0.7 g/day), BMR (52.5 ± 6.0 ml O2/h), ACswim (257.2 ± 30.5 ml O2/h) and ACcold (270.5 ± 37.3 ml O2/h) varied remarkably among individuals. Food consumption increased with body mass of individuals (r = 0.53, p b 0.001) and with body mass gain during the trail (r = 0.31, p b 0.001). Narrow-sense heritability of mass-independent food consumption (corrected also for body mass changes) was 0.19 (p b 0.001). There is a positive additive genetic correlation between the food consumption and BMR (rA = 0.46) and ACswim (rA = 0.49), and there is no evidence for the genetic correlation between food consumption and ACcold. The results are consistent with a hypothesis that high BMR and endothermy in mammals evolved in connection with evolution of locomotor capabilities and high overall daily