10.5061/DRYAD.SJ3TX9638
Swanson, David
0000-0003-2258-7335
University of South Dakota
IOB-2020-008_HouseSparrow
Dryad
dataset
2020
Environmental physiology
National Science Foundation
https://ror.org/021nxhr62
IOS-1021218
2020-10-22T00:00:00Z
2020-10-22T00:00:00Z
en
48285 bytes
2
CC0 1.0 Universal (CC0 1.0) Public Domain Dedication
The climatic variability hypothesis (CVH) posits that more flexible
phenotypes should provide a fitness advantage for organisms experiencing
more variable climates. While typically applied across geographically
separated populations, whether this principle applies across seasons or
other conditions (e.g., open vs. sheltered habitats) which differ in
climatic variability remains essentially unstudied. In north-temperate
climates, climatic variability in winter usually exceeds that in summer,
so extending the CVH to within-population seasonal variation predicts that
winter phenotypes should be more flexible than summer phenotypes. We
tested this prediction of the within-season extension of the CVH by
acclimating summer and winter-collected house sparrows (Passer domesticus)
to 24, 5 and -10°C and measuring basal (BMR) and summit (Msum = maximum
cold-induced) metabolic rates before and after acclimation. To examine
mechanistic bases for metabolic variation, we measured flight muscle and
heart masses and citrate synthase and β-hydroxyacyl coA-dehydrogenase
activities. BMR and Msum were higher for cold-acclimated than for
warm-acclimated birds and BMR was higher in winter than in summer birds.
Contrary to our hypothesis of greater responses to cold acclimation in
winter birds, metabolic rates generally decreased over the acclimation
period for winter birds at all temperatures but increased at cold
temperatures for summer birds. Flight muscle and heart masses were not
significantly correlated with season or acclimation treatment, except for
supracoracoideus mass, which was lower at -10°C in winter, but flight
muscle and heart masses were positively correlated with BMR and flight
muscle mass was positively correlated with Msum. Catabolic enzyme
activities were not clearly related to metabolic variation. Thus, our data
suggest that predictions of the CVH may not be relevant when extended to
seasonal temperature variability at the within-population scale. Indeed,
these data suggest that metabolic rates are more prominently upregulated
in summer than in winter in response to cold. Metabolic rates tended to
decrease during acclimation at all temperatures in winter, suggesting that
initial metabolic rates at capture (higher in winter) influence metabolic
acclimation for captive birds.
House Sparrows acclimated to different temperature conditions (24, 5, and
-10 C) for six weeks in both summer and winter. Data collected included
basal and summit metabolic rates (pre, mid and post-acclimation),
ultrasound flight muscle width (pre and post-acclimation), and tissue
masses and catabolic enzyme activities (post-acclimation).
There are scattered missing values for some of these variables. They
appear as blank cells in the Excel file.