Among- and within-individual correlations between basal and maximal metabolic rates in birds

Abstract

The aerobic capacity model proposes that endothermy is a byproduct of selection favouring high maximal metabolic rates (MMR) and its mechanistic coupling with basal metabolic rate (BMR). Attempts to validate this model in birds are equivocal and restricted to phenotypic correlations (r P ), thus failing to distinguish among-and within-individual correlations (r ind and r e ). We examined 300 paired measurements of BMR and MMR from 60 house sparrows before and after two levels of experimental manipulation -testosterone implants and immune challenge. Overall, repeatability was significant in both BMR (R=0.25±0.06) and MMR (R=0.52±0.06). Only the testosterone treatment altered the r P between BMR and MMR, which resulted from contrasting effects on r ind and r e . While r ind was high and significant (0.62±0.22) in sham-implanted birds, r e was negative and marginally non-significant (−0.15±0.09) in testosterone-treated birds. Thus, the expected mechanistic link between BMR and MMR was apparent, but only in birds with low testosterone levels.

Variation in Metabolic Rate among Individuals Is Related to Tissue-Specific Differences in Mitochondrial Leak Respiration

“…We found no correlation between SMR and MMR among fish or between the mitochondrial properties of the liver and white muscle. The absence of covariation between tissues supports earlier findings (Garland 1984;Garland and Else 1987;Park et al 2014), while the lack of any correlation between minimum metabolic rate and MMR has also been found elsewhere (Chappell et al 2004(Chappell et al , 2007Gomes et al 2004;Careau et al 2014b). However, a highly original finding was the evidence of clear differences between liver and muscle in terms of the relationship between their mitochondrial properties and whole-organism metabolic Note.…”

“…However, while a positive correlation between minimum and maximum metabolic rates at the intraspecific level has indeed been found in some contexts Biro and Stamps 2010;Careau et al 2014aCareau et al , 2014b, this is not the case in others (Chappell et al 2004(Chappell et al , 2007Gomes et al 2004;Careau et al 2014b). The mechanisms underlying this purported link are also equivocal, with some studies reporting a positive relationship between metabolic rates and underlying traits such as organ size (Konarzewski and Ksiazek 2013) or mitochondrial density (Norin and Malte 2012), whereas others find no relationship (Selman et al 2001;Chappell et al 2007;Larsen et al 2011;Norin and Malte 2012;Boldsen et al 2013).…”

“…Therefore, AS may have a significant impact on fitness but displays significant intraspecific variation (Farrell et al 2008;Sandblom et al 2014;Auer et al 2015aAuer et al , 2015c; but see Norin et al 2014). Both minimum and maximum metabolic rate are responsible for intraspecific variation in AS since they exhibit consistent differences among individuals over extended periods of time, even within a population under standardized conditions Burton et al 2011;Swanson et al 2012;Careau et al 2014aCareau et al , 2014bGifford et al 2014). In turn, the use of a single metric such as AS conceals a great deal of variation, since individuals with the same AS can have markedly different absolute levels of minimum and maximum metabolic rate (Auer et al 2015c).…”

Individual variation in metabolic reaction norms over ambient temperature causes low correlation between basal and standard metabolic rate

“…The repeatability of whole-organism metabolic rate in the range 0.4-0.5 found here are consistent with the existing literature, with most repeatabilities ranging between 0.3 and 0.8 (Auer et al, 2016;Nespolo and Franco, 2007;Versteegh et al, 2008;White et al, 2013). Our repeatability of mass-adjusted metabolic rate, ranging between 0.3 and 0.4, is also consistent with earlier studies in birds, although perhaps on the lower range relative to that found in earlier zebra finch studies, which was between 0.3 and 0.6 (Careau et al, 2014;Rønning et al, 2005;Verhulst et al, 2006;Vézina and Williams, 2005). Two aspects of our study are likely to have contributed to this difference.…”

Cross-training in birds: cold and exercise training produce similar changes in maximal metabolic output, muscle masses and myostatin expression in house sparrows,Passer domesticus

“…Consequently, correlations between maximum metabolic rates during exercise (MMR) and cold (summit metabolic rate, M sum ) might be expected both among and within species (Swanson, 2010). However, only a few studies have examined relationships among basal metabolic rate (BMR, lower limit of metabolic output), MMR and M sum (Wiersma et al, 2007;Swanson et al, 2012;Petit et al, 2013;Careau et al, 2014) and these studies fail to show consistent correlations among BMR, MMR and M sum . To our knowledge, no studies have explicitly examined cross-training effects (i.e.…”