Data from: Metabolic rate covaries with fitness and the pace of the life history in the field

Metabolic rate reflects the ‘pace of life’ in every organism. Metabolic
rate is related to an organism's capacity for essential maintenance,
growth and reproduction—all of which interact to affect fitness. Although
thousands of measurements of metabolic rate have been made, the
microevolutionary forces that shape metabolic rate remain poorly resolved.
The relationship between metabolic rate and components of fitness are
often inconsistent, possibly because these fitness components incompletely
map to actual fitness and often negatively covary with each other. Here we
measure metabolic rate across ontogeny and monitor its effects on actual
fitness (lifetime reproductive output) for a marine bryozoan in the field.
We also measure key components of fitness throughout the entire life
history including growth rate, longevity and age at the onset of
reproduction. We found that correlational selection favours individuals
with higher metabolic rates in one stage and lower metabolic rates in the
other—individuals with similar metabolic rates in each developmental stage
displayed the lowest fitness. Furthermore, individuals with the lowest
metabolic rates lived for longer and reproduced more, but they also grew
more slowly and took longer to reproduce initially. That metabolic rate is
related to the pace of the life history in nature has long been suggested
by macroevolutionary patterns but this study reveals the microevolutionary
processes that probably generated these patterns.