James Mclister - Academia.edu (original) (raw)
Papers by James Mclister
Behavioral Ecology and Sociobiology, 2022
A table showing nutrient composition of control and creosote diets (% dry matter).
A table showing nutrient and chemical composition of control and juniper diets (dry matter).
An explanation of calculations for individual component of the energetic cost of toxins (ECT, kJ/d).
Journal of Experimental Biology, 2001
The metabolic cost, energy output and efficiency (i.e. the ratio of energy output to metabolic co... more The metabolic cost, energy output and efficiency (i.e. the ratio of energy output to metabolic cost) of sound production were compared among male grey treefrogs (Hyla versicolor) as a function of body size and temperature. The effects of call length (in notes per call) and dominant frequency (in kHz) were also considered. Cost, determined from the amount of oxygen consumed, averaged 12.1 mJ per note and was dependent only upon body mass. Acoustic energy per note, determined from oscillograms of recorded calls, averaged 0.34 mJ and was dependent only upon temperature. Conventional theory suggests that the efficiency of sound production should be a function of the ratio of the linear size of the radiating structures to the wavelength of the sound generated (i.e. efficiency is assumed to be a function of the product of mass(0.33) and frequency), but efficiency in H. versicolor was found to be a function of the product of temperature(2.1) and mass(−1.08). Adjusting for temperature and b...
Canadian Journal of Zoology, 2003
The metabolic cost of amplexus was calculated for 37 pairs of grey tree frogs, Hyla versicolor, b... more The metabolic cost of amplexus was calculated for 37 pairs of grey tree frogs, Hyla versicolor, by measuring the rate of O2consumption of each amplexed pair and the combined resting rates of O2consumption of the two individuals of each pair, and calculating the difference. The mean cost of amplexus was 1.20 mL O2·h1for each pair. The cost of amplexus was correlated with the mass of the males but not the mass of the females, and amplexus with artificial males did not have a significant effect on female metabolic rate. Therefore, the cost of amplexus appears to be incurred entirely by the male. Reproductively successful males spend less time calling per evening than reproductively unsuccessful males, leaving the chorus early to enter into amplexus. The mass-specific cost of amplexus (0.158 mL O2·g1·h1) is approximately 1/10 the mass-specific cost of call production (1.620 mL O2·g1·h1), and net energy consumption per evening is less for reproductively successful male H. versicolor...
Physiological Zoology, 1996
ABSTRACT
The Journal of experimental biology, 1995
Isometric twitch and tetanus parameters, force-velocity curves, maximum shortening velocity (Vmax... more Isometric twitch and tetanus parameters, force-velocity curves, maximum shortening velocity (Vmax) and percentage relaxation between stimuli (%R) across a range of stimulus frequencies were determined for a muscle used during call production (the tensor chordarum) and a locomotor muscle (the sartorius) for three species of hylid frogs, Hyla chrysoscelis, H. versicolor and H. cinerea. The call of H. chrysoscelis has a note repetition rate (NRR) approximately twice as fast as the call of H. versicolor (28.3, 42.5 and 56.8 notes s-1 for H. chrysoscelis and 14.8, 21.1 and 27.4 notes s-1 for H. versicolor at 15, 20 and 25 degrees C, respectively). Hyla cinerea calls at a very slow NRR (Approximately 3 notes s-1 at 25 degrees C). Hyla versicolor evolved from H. chrysoscelis via autopolyploidy, so the mating call of H. chrysoscelis is presumably the ancestral mating call of H. versicolor. For the tensor chordarum of H. chrysoscelis, H. versicolor and H. cinerea at 25 degrees C, mean twitch...
Physiological and Biochemical Zoology, 2004
A study was done to test whether toxic plants that occur naturally in the diet affect thermoregul... more A study was done to test whether toxic plants that occur naturally in the diet affect thermoregulation in mammalian herbivores. The woodrats Neotoma albigula and Neotoma stephensi both consume juniper (Juniperus monosperma), a plant with high levels of toxic compounds. Body temperature (T b ), basal metabolic rate (BMR), and the minimum cost of thermogenesis (C min ) were measured for both species on control and juniper diets following warm (25ЊC) and cold (18ЊC) acclimation. In N. albigula, diet had no uniform effect on T b , BMR, or C min , but -temperature interaction effects on T b diet # acclimation and C min were highly significant ( ). For thermoregu-P ! 0.005 lation at 15ЊC, juniper consumption increased the metabolic cost for warm-acclimated N. albigula by 50% but decreased the metabolic cost in cold-acclimated N. albigula by 24%. In N. stephensi, diet significantly affected T b and C min ( ), but P ! 0.05 there were no significant -temperature in-diet # acclimation teraction effects. For thermoregulation at 15ЊC, juniper consumption increased the metabolic cost for warm-acclimated N. stephensi by 33% but had no significant effect on metabolic cost in cold-acclimated N. stephensi.
Physiological and Biochemical Zoology, 2008
The whitethroat woodrat (Neotoma albigula) eats juniper (Juniperus monosperma), but the amount of... more The whitethroat woodrat (Neotoma albigula) eats juniper (Juniperus monosperma), but the amount of juniper in its diet varies seasonally. We tested whether changes in juniper consumption are due to changes in ambient temperature and what the physiological consequences of consuming plant secondary compounds (PSCs) at different ambient temperatures might be. Woodrats were acclimated to either 20ЊC or 28ЊC. Later, they were given two diets to choose from (50% juniper and a nontoxic control) for 7 d. Food intake, resting metabolic rate (RMR), and body temperature (T b ) were measured over the last 2 d. Woodrats at 28ЊC ate significantly less juniper, both proportionally and absolutely, than woodrats at 20ЊC. RMRs were higher for woodrats consuming juniper regardless of ambient temperature, and T b was higher for woodrats consuming juniper at 28ЊC than for woodrats eating control diet at 28ЊC. Thus, juniper consumption by N. albigula is influenced by ambient temperature. We conclude that juniper may influence thermoregulation in N. albigula in ways that are helpful at low temperatures but harmful at warmer temperatures in that juniper PSCs may be more toxic at warmer temperatures. The results suggest that increases in ambient temperature associated with climate change could significantly influence foraging behavior of mammalian herbivores.
Journal of Comparative Physiology B, 2005
The acquisition of adequate quantities of nitrogen is a challenge for herbivorous vertebrates bec... more The acquisition of adequate quantities of nitrogen is a challenge for herbivorous vertebrates because many plants are in low nitrogen and contain secondary metabolites that reduce nitrogen digestibility. To investigate whether herbivores maintain nitrogen balance on plant diets low in nitrogen and high in secondary compounds, we studied the effect of juniper (Juniperus monosperma) ingestion on the nitrogen balance of two species of herbivorous woodrats (Neotoma stephensi and N. albigula). These woodrat species feed on the foliage of juniper: N. stephensi is a juniper specialist, whereas N. albigula is a generalist that incorporates some juniper in its diet. Based on the nitrogen contents of the natural diets of these woodrats, we predicted that the generalist would be in negative nitrogen balance on a juniper diet whereas the specialist would not be affected. We found that both species of woodrat had low-nitrogen requirements (334.2 mg N/kg 0.75 /day) and that a diet of 50% juniper did not result in negative nitrogen balance for either species. However, excretion patterns of nitrogen were altered; on the 50% juniper diet, fecal nitrogen losses increased $38% and urinary nitrogen losses were half that of the control diet. The results suggest that absorption and detoxification of juniper secondary compounds may be more important for restricting juniper intake by the generalist than nitrogen imbalance.
Ecology, 2005
Theory predicts that dietary specialization is limited in part because of physiological trade-off... more Theory predicts that dietary specialization is limited in part because of physiological trade-offs associated with specialization. Specifically, dietary specialists are predicted to evolve mechanisms that reduce costs and enhance excretion of plant secondary metabolites (PSMs) that they frequently consume, but are less energetically and/or mechanistically efficient at eliminating novel PSMs. Although examples of trade-offs associated with dietary specialization have been documented among insects, trade-offs have not been investigated in mammalian herbivores. To initially investigate the physiological trade-offs associated with specialization in mammalian herbivores, we determined the impact of ingesting novel PSMs on the energy budgets of a juniper specialist (Neotoma stephensi) and generalist (N. albigula) woodrat. These results were then compared to the impact of juniper intake, the plant species preferred by the specialist, on energy budgets in these same species. Energy budgets were evaluated by measuring apparent metabolizable energy intake (AMEI, energy consumed Ϫ energy excreted) and energy expended on basal metabolic rate (BMR) and voluntary wheel running in specialist and generalist woodrats fed a formulated diet with and without PSMs from the novel plant creosote (Larrea tridentata). Both specialists and generalists were energetically impacted by the intake of a diet containing novel PSMs, primarily through decreased intake of creosote diet and increased excretion of energy in the urine. However, specialists were impacted to a greater extent than generalists. Specialists decreased body mass, whereas generalists maintained body mass. Specialists also reduced intake and AMEI when consuming creosote diet compared to control to a greater extent than generalists. In turn, specialists had one-sixth the energy available for energy dependent activities than generalists on a diet containing novel PSMs. These results are in stark contrast to the comparisons between specialists and generalists consuming PSMs from their natural diet. Specialists consumed more juniper, had higher AMEI and available energy than generalists when fed diets containing juniper foliage. These data provide the first support that physiological trade-offs associated with dietary specialization may exist in mammalian herbivores.
Ecology, 2005
Ingestion of plant secondary metabolites (PSMs) presents a physiological and behavioral challenge... more Ingestion of plant secondary metabolites (PSMs) presents a physiological and behavioral challenge for mammalian herbivores. Herbivores must not only detoxify PSMs, but they may also deal with energetic constraints such as reduced food intake, mass loss, increased excretion of energy, and increased metabolic demands. We hypothesized that the energetic consequences of consuming PSMs will significantly compromise apparent metabolizable energy intake (AMEI) and energy expenditure in mammalian herbivores. Furthermore, we hypothesized that foraging strategy would influence the degree to which plant consumption impacts energy budgets, such that dietary specialists would be less impacted than generalists when both are consuming the plant species preferred by the specialist. Hypotheses were tested by comparing AMEI and energy expended on basal metabolic rate (BMR) and locomotion in a juniper specialist (Neotoma stephensi) and generalist (N. albigula) woodrat fed control diet and diet containing juniper foliage (Juniperus monosperma). In general, the intake of PSMs in juniper increased the energy excreted in urine and feces in both specialist and generalist woodrats. Specialist woodrats minimized the costs associated with the intake of juniper by ingesting more juniper diet, thereby increasing energy intake, and reducing energy expended on BMR and locomotor activity. Generalist woodrats also decreased locomotor activity on a juniper diet but did not increase intake and maintained BMR. In turn, specialist woodrats had twice as much energy available for activities such as reproduction when consuming a juniper diet than generalists. These results suggest that the intake of PSMs impinges on AMEI and compromises energy expenditure, but that the impact of PSMs on energy budgets is relative to ecological experience with PSMs. Moreover, compensatory feeding, metabolic depression, and low activity may be strategies employed by specialist woodrats that can mitigate the cost of processing PSMs, but these strategies may be constrained in generalist woodrats.
Canadian Journal of Zoology, 1991
Behavioral Ecology and Sociobiology, 2022
A table showing nutrient composition of control and creosote diets (% dry matter).
A table showing nutrient and chemical composition of control and juniper diets (dry matter).
An explanation of calculations for individual component of the energetic cost of toxins (ECT, kJ/d).
Journal of Experimental Biology, 2001
The metabolic cost, energy output and efficiency (i.e. the ratio of energy output to metabolic co... more The metabolic cost, energy output and efficiency (i.e. the ratio of energy output to metabolic cost) of sound production were compared among male grey treefrogs (Hyla versicolor) as a function of body size and temperature. The effects of call length (in notes per call) and dominant frequency (in kHz) were also considered. Cost, determined from the amount of oxygen consumed, averaged 12.1 mJ per note and was dependent only upon body mass. Acoustic energy per note, determined from oscillograms of recorded calls, averaged 0.34 mJ and was dependent only upon temperature. Conventional theory suggests that the efficiency of sound production should be a function of the ratio of the linear size of the radiating structures to the wavelength of the sound generated (i.e. efficiency is assumed to be a function of the product of mass(0.33) and frequency), but efficiency in H. versicolor was found to be a function of the product of temperature(2.1) and mass(−1.08). Adjusting for temperature and b...
Canadian Journal of Zoology, 2003
The metabolic cost of amplexus was calculated for 37 pairs of grey tree frogs, Hyla versicolor, b... more The metabolic cost of amplexus was calculated for 37 pairs of grey tree frogs, Hyla versicolor, by measuring the rate of O2consumption of each amplexed pair and the combined resting rates of O2consumption of the two individuals of each pair, and calculating the difference. The mean cost of amplexus was 1.20 mL O2·h1for each pair. The cost of amplexus was correlated with the mass of the males but not the mass of the females, and amplexus with artificial males did not have a significant effect on female metabolic rate. Therefore, the cost of amplexus appears to be incurred entirely by the male. Reproductively successful males spend less time calling per evening than reproductively unsuccessful males, leaving the chorus early to enter into amplexus. The mass-specific cost of amplexus (0.158 mL O2·g1·h1) is approximately 1/10 the mass-specific cost of call production (1.620 mL O2·g1·h1), and net energy consumption per evening is less for reproductively successful male H. versicolor...
Physiological Zoology, 1996
ABSTRACT
The Journal of experimental biology, 1995
Isometric twitch and tetanus parameters, force-velocity curves, maximum shortening velocity (Vmax... more Isometric twitch and tetanus parameters, force-velocity curves, maximum shortening velocity (Vmax) and percentage relaxation between stimuli (%R) across a range of stimulus frequencies were determined for a muscle used during call production (the tensor chordarum) and a locomotor muscle (the sartorius) for three species of hylid frogs, Hyla chrysoscelis, H. versicolor and H. cinerea. The call of H. chrysoscelis has a note repetition rate (NRR) approximately twice as fast as the call of H. versicolor (28.3, 42.5 and 56.8 notes s-1 for H. chrysoscelis and 14.8, 21.1 and 27.4 notes s-1 for H. versicolor at 15, 20 and 25 degrees C, respectively). Hyla cinerea calls at a very slow NRR (Approximately 3 notes s-1 at 25 degrees C). Hyla versicolor evolved from H. chrysoscelis via autopolyploidy, so the mating call of H. chrysoscelis is presumably the ancestral mating call of H. versicolor. For the tensor chordarum of H. chrysoscelis, H. versicolor and H. cinerea at 25 degrees C, mean twitch...
Physiological and Biochemical Zoology, 2004
A study was done to test whether toxic plants that occur naturally in the diet affect thermoregul... more A study was done to test whether toxic plants that occur naturally in the diet affect thermoregulation in mammalian herbivores. The woodrats Neotoma albigula and Neotoma stephensi both consume juniper (Juniperus monosperma), a plant with high levels of toxic compounds. Body temperature (T b ), basal metabolic rate (BMR), and the minimum cost of thermogenesis (C min ) were measured for both species on control and juniper diets following warm (25ЊC) and cold (18ЊC) acclimation. In N. albigula, diet had no uniform effect on T b , BMR, or C min , but -temperature interaction effects on T b diet # acclimation and C min were highly significant ( ). For thermoregu-P ! 0.005 lation at 15ЊC, juniper consumption increased the metabolic cost for warm-acclimated N. albigula by 50% but decreased the metabolic cost in cold-acclimated N. albigula by 24%. In N. stephensi, diet significantly affected T b and C min ( ), but P ! 0.05 there were no significant -temperature in-diet # acclimation teraction effects. For thermoregulation at 15ЊC, juniper consumption increased the metabolic cost for warm-acclimated N. stephensi by 33% but had no significant effect on metabolic cost in cold-acclimated N. stephensi.
Physiological and Biochemical Zoology, 2008
The whitethroat woodrat (Neotoma albigula) eats juniper (Juniperus monosperma), but the amount of... more The whitethroat woodrat (Neotoma albigula) eats juniper (Juniperus monosperma), but the amount of juniper in its diet varies seasonally. We tested whether changes in juniper consumption are due to changes in ambient temperature and what the physiological consequences of consuming plant secondary compounds (PSCs) at different ambient temperatures might be. Woodrats were acclimated to either 20ЊC or 28ЊC. Later, they were given two diets to choose from (50% juniper and a nontoxic control) for 7 d. Food intake, resting metabolic rate (RMR), and body temperature (T b ) were measured over the last 2 d. Woodrats at 28ЊC ate significantly less juniper, both proportionally and absolutely, than woodrats at 20ЊC. RMRs were higher for woodrats consuming juniper regardless of ambient temperature, and T b was higher for woodrats consuming juniper at 28ЊC than for woodrats eating control diet at 28ЊC. Thus, juniper consumption by N. albigula is influenced by ambient temperature. We conclude that juniper may influence thermoregulation in N. albigula in ways that are helpful at low temperatures but harmful at warmer temperatures in that juniper PSCs may be more toxic at warmer temperatures. The results suggest that increases in ambient temperature associated with climate change could significantly influence foraging behavior of mammalian herbivores.
Journal of Comparative Physiology B, 2005
The acquisition of adequate quantities of nitrogen is a challenge for herbivorous vertebrates bec... more The acquisition of adequate quantities of nitrogen is a challenge for herbivorous vertebrates because many plants are in low nitrogen and contain secondary metabolites that reduce nitrogen digestibility. To investigate whether herbivores maintain nitrogen balance on plant diets low in nitrogen and high in secondary compounds, we studied the effect of juniper (Juniperus monosperma) ingestion on the nitrogen balance of two species of herbivorous woodrats (Neotoma stephensi and N. albigula). These woodrat species feed on the foliage of juniper: N. stephensi is a juniper specialist, whereas N. albigula is a generalist that incorporates some juniper in its diet. Based on the nitrogen contents of the natural diets of these woodrats, we predicted that the generalist would be in negative nitrogen balance on a juniper diet whereas the specialist would not be affected. We found that both species of woodrat had low-nitrogen requirements (334.2 mg N/kg 0.75 /day) and that a diet of 50% juniper did not result in negative nitrogen balance for either species. However, excretion patterns of nitrogen were altered; on the 50% juniper diet, fecal nitrogen losses increased $38% and urinary nitrogen losses were half that of the control diet. The results suggest that absorption and detoxification of juniper secondary compounds may be more important for restricting juniper intake by the generalist than nitrogen imbalance.
Ecology, 2005
Theory predicts that dietary specialization is limited in part because of physiological trade-off... more Theory predicts that dietary specialization is limited in part because of physiological trade-offs associated with specialization. Specifically, dietary specialists are predicted to evolve mechanisms that reduce costs and enhance excretion of plant secondary metabolites (PSMs) that they frequently consume, but are less energetically and/or mechanistically efficient at eliminating novel PSMs. Although examples of trade-offs associated with dietary specialization have been documented among insects, trade-offs have not been investigated in mammalian herbivores. To initially investigate the physiological trade-offs associated with specialization in mammalian herbivores, we determined the impact of ingesting novel PSMs on the energy budgets of a juniper specialist (Neotoma stephensi) and generalist (N. albigula) woodrat. These results were then compared to the impact of juniper intake, the plant species preferred by the specialist, on energy budgets in these same species. Energy budgets were evaluated by measuring apparent metabolizable energy intake (AMEI, energy consumed Ϫ energy excreted) and energy expended on basal metabolic rate (BMR) and voluntary wheel running in specialist and generalist woodrats fed a formulated diet with and without PSMs from the novel plant creosote (Larrea tridentata). Both specialists and generalists were energetically impacted by the intake of a diet containing novel PSMs, primarily through decreased intake of creosote diet and increased excretion of energy in the urine. However, specialists were impacted to a greater extent than generalists. Specialists decreased body mass, whereas generalists maintained body mass. Specialists also reduced intake and AMEI when consuming creosote diet compared to control to a greater extent than generalists. In turn, specialists had one-sixth the energy available for energy dependent activities than generalists on a diet containing novel PSMs. These results are in stark contrast to the comparisons between specialists and generalists consuming PSMs from their natural diet. Specialists consumed more juniper, had higher AMEI and available energy than generalists when fed diets containing juniper foliage. These data provide the first support that physiological trade-offs associated with dietary specialization may exist in mammalian herbivores.
Ecology, 2005
Ingestion of plant secondary metabolites (PSMs) presents a physiological and behavioral challenge... more Ingestion of plant secondary metabolites (PSMs) presents a physiological and behavioral challenge for mammalian herbivores. Herbivores must not only detoxify PSMs, but they may also deal with energetic constraints such as reduced food intake, mass loss, increased excretion of energy, and increased metabolic demands. We hypothesized that the energetic consequences of consuming PSMs will significantly compromise apparent metabolizable energy intake (AMEI) and energy expenditure in mammalian herbivores. Furthermore, we hypothesized that foraging strategy would influence the degree to which plant consumption impacts energy budgets, such that dietary specialists would be less impacted than generalists when both are consuming the plant species preferred by the specialist. Hypotheses were tested by comparing AMEI and energy expended on basal metabolic rate (BMR) and locomotion in a juniper specialist (Neotoma stephensi) and generalist (N. albigula) woodrat fed control diet and diet containing juniper foliage (Juniperus monosperma). In general, the intake of PSMs in juniper increased the energy excreted in urine and feces in both specialist and generalist woodrats. Specialist woodrats minimized the costs associated with the intake of juniper by ingesting more juniper diet, thereby increasing energy intake, and reducing energy expended on BMR and locomotor activity. Generalist woodrats also decreased locomotor activity on a juniper diet but did not increase intake and maintained BMR. In turn, specialist woodrats had twice as much energy available for activities such as reproduction when consuming a juniper diet than generalists. These results suggest that the intake of PSMs impinges on AMEI and compromises energy expenditure, but that the impact of PSMs on energy budgets is relative to ecological experience with PSMs. Moreover, compensatory feeding, metabolic depression, and low activity may be strategies employed by specialist woodrats that can mitigate the cost of processing PSMs, but these strategies may be constrained in generalist woodrats.
Canadian Journal of Zoology, 1991