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Environment, migratory tendency, phylogeny and basal metabolic rate in birds.

Jetz W, Freckleton RP, McKechnie AE - PLoS ONE (2008)

Bottom Line: Among several environmental predictors, average annual temperature has the strongest effect on BMR, with a 50% reduction associated with a 20 degrees C gradient.In contrast to the findings of previous analyses of mammalian BMR, primary productivity, aridity or precipitation variability do not appear to be important environmental correlates of avian BMR.The strong effects of temperature-related variables and varying phylogenetic effects reiterate the importance of addressing both broad-scale and individual-scale variation for understanding the determinants of BMR.

View Article: PubMed Central - PubMed

Affiliation: Division of Biological Sciences, University of California San Diego, La Jolla, California, USA. wjetz@ucsd.edu

ABSTRACT
Basal metabolic rate (BMR) represents the minimum maintenance energy requirement of an endotherm and has far-reaching consequences for interactions between animals and their environments. Avian BMR exhibits considerable variation that is independent of body mass. Some long-distance migrants have been found to exhibit particularly high BMR, traditionally interpreted as being related to the energetic demands of long-distance migration. Here we use a global dataset to evaluate differences in BMR between migrants and non-migrants, and to examine the effects of environmental variables. The BMR of migrant species is significantly higher than that of non-migrants. Intriguingly, while the elevated BMR of migrants on their breeding grounds may reflect the metabolic machinery required for long-distance movements, an alternative (and statistically stronger) explanation is their occupation of predominantly cold high-latitude breeding areas. Among several environmental predictors, average annual temperature has the strongest effect on BMR, with a 50% reduction associated with a 20 degrees C gradient. The negative effects of temperature variables on BMR hold separately for migrants and non-migrants and are not due their different climatic associations. BMR in migrants shows a much lower degree of phylogenetic inertia. Our findings indicate that migratory tendency need not necessarily be invoked to explain the higher BMR of migrants. A weaker phylogenetic signal observed in migrants supports the notion of strong phenotypic flexibility in this group which facilitates migration-related BMR adjustments that occur above and beyond environmental conditions. In contrast to the findings of previous analyses of mammalian BMR, primary productivity, aridity or precipitation variability do not appear to be important environmental correlates of avian BMR. The strong effects of temperature-related variables and varying phylogenetic effects reiterate the importance of addressing both broad-scale and individual-scale variation for understanding the determinants of BMR.

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Avian BMR increases with body mass, and is higher in migrants than non-migrants.A Individual data points and partial regression fits for non-migrants (black, solid line) and migrants (open, dotted line). B average residuals (±s.e.) from the overall regression of log BMR on log body mass for non-migrants and migrants. Full dataset (N = 135).
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pone-0003261-g001: Avian BMR increases with body mass, and is higher in migrants than non-migrants.A Individual data points and partial regression fits for non-migrants (black, solid line) and migrants (open, dotted line). B average residuals (±s.e.) from the overall regression of log BMR on log body mass for non-migrants and migrants. Full dataset (N = 135).

Mentions: We first use the full dataset (N = 135) without phylogenetic control to illustrate core correlates of avian basal metabolic rate (BMR) and to demonstrate the significance of migratory tendency. Confirming previous studies we find that in a two-predictor model BMR increases consistently and strongly with body mass (M: b = 0.744, t = 30.89, p<0.001) and is additionally significantly higher in Passerines than Non-Passerines (Pass/non-p.: b = 0.082, t = 5.595, p<0.001). We first test for a potential effect of migratory tendency on BMR only controlling for body mass (Fig. 1). We find that in migrants BMR is much higher than in non-migrant birds (Migratory: b = 0.044, t = 3.93, p<0.001). The effect of migratory tendency is confirmed in the three-predictor model controlling for Pass/non-p. membership which yields the best overall fit (Migratory: b = 0.032, t = 3.05, p<0.01, full model adjusted r2 = 0.912). Refinement of the binary migratory tendency variable to a three-level distinction of non-migrant, short and long-distance migrants did not significantly improve the model fit suggesting that BMR did not differ between those two broad categories of migration distance.


Environment, migratory tendency, phylogeny and basal metabolic rate in birds.

Jetz W, Freckleton RP, McKechnie AE - PLoS ONE (2008)

Avian BMR increases with body mass, and is higher in migrants than non-migrants.A Individual data points and partial regression fits for non-migrants (black, solid line) and migrants (open, dotted line). B average residuals (±s.e.) from the overall regression of log BMR on log body mass for non-migrants and migrants. Full dataset (N = 135).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2533122&req=5

pone-0003261-g001: Avian BMR increases with body mass, and is higher in migrants than non-migrants.A Individual data points and partial regression fits for non-migrants (black, solid line) and migrants (open, dotted line). B average residuals (±s.e.) from the overall regression of log BMR on log body mass for non-migrants and migrants. Full dataset (N = 135).
Mentions: We first use the full dataset (N = 135) without phylogenetic control to illustrate core correlates of avian basal metabolic rate (BMR) and to demonstrate the significance of migratory tendency. Confirming previous studies we find that in a two-predictor model BMR increases consistently and strongly with body mass (M: b = 0.744, t = 30.89, p<0.001) and is additionally significantly higher in Passerines than Non-Passerines (Pass/non-p.: b = 0.082, t = 5.595, p<0.001). We first test for a potential effect of migratory tendency on BMR only controlling for body mass (Fig. 1). We find that in migrants BMR is much higher than in non-migrant birds (Migratory: b = 0.044, t = 3.93, p<0.001). The effect of migratory tendency is confirmed in the three-predictor model controlling for Pass/non-p. membership which yields the best overall fit (Migratory: b = 0.032, t = 3.05, p<0.01, full model adjusted r2 = 0.912). Refinement of the binary migratory tendency variable to a three-level distinction of non-migrant, short and long-distance migrants did not significantly improve the model fit suggesting that BMR did not differ between those two broad categories of migration distance.

Bottom Line: Among several environmental predictors, average annual temperature has the strongest effect on BMR, with a 50% reduction associated with a 20 degrees C gradient.In contrast to the findings of previous analyses of mammalian BMR, primary productivity, aridity or precipitation variability do not appear to be important environmental correlates of avian BMR.The strong effects of temperature-related variables and varying phylogenetic effects reiterate the importance of addressing both broad-scale and individual-scale variation for understanding the determinants of BMR.

View Article: PubMed Central - PubMed

Affiliation: Division of Biological Sciences, University of California San Diego, La Jolla, California, USA. wjetz@ucsd.edu

ABSTRACT
Basal metabolic rate (BMR) represents the minimum maintenance energy requirement of an endotherm and has far-reaching consequences for interactions between animals and their environments. Avian BMR exhibits considerable variation that is independent of body mass. Some long-distance migrants have been found to exhibit particularly high BMR, traditionally interpreted as being related to the energetic demands of long-distance migration. Here we use a global dataset to evaluate differences in BMR between migrants and non-migrants, and to examine the effects of environmental variables. The BMR of migrant species is significantly higher than that of non-migrants. Intriguingly, while the elevated BMR of migrants on their breeding grounds may reflect the metabolic machinery required for long-distance movements, an alternative (and statistically stronger) explanation is their occupation of predominantly cold high-latitude breeding areas. Among several environmental predictors, average annual temperature has the strongest effect on BMR, with a 50% reduction associated with a 20 degrees C gradient. The negative effects of temperature variables on BMR hold separately for migrants and non-migrants and are not due their different climatic associations. BMR in migrants shows a much lower degree of phylogenetic inertia. Our findings indicate that migratory tendency need not necessarily be invoked to explain the higher BMR of migrants. A weaker phylogenetic signal observed in migrants supports the notion of strong phenotypic flexibility in this group which facilitates migration-related BMR adjustments that occur above and beyond environmental conditions. In contrast to the findings of previous analyses of mammalian BMR, primary productivity, aridity or precipitation variability do not appear to be important environmental correlates of avian BMR. The strong effects of temperature-related variables and varying phylogenetic effects reiterate the importance of addressing both broad-scale and individual-scale variation for understanding the determinants of BMR.

Show MeSH
Related in: MedlinePlus