DOI: 10.5061/dryad.63xsj3v17
title: Quantifying selection on standard metabolic rate and body mass in Drosophila melanogaster

description: Standard metabolic rate (SMR), defined as the minimal energy expenditure
 required for self-maintenance, is a key physiological trait. Few studies
 have estimated its relationship with fitness, most notably in insects.
 This is presumably due to the difficulty of measuring SMR in a large
 number of very small individuals. Using high-throughput flow-through
 respirometry and a Drosophila melanogaster laboratory population adapted
 to a life-cycle that facilitates fitness measures, we quantified SMR, body
 mass, and fitness in 515 female and 522 male adults. We used a novel
 multivariate approach to estimate linear and non-linear selection
 differentials and gradients from the variance-covariance matrix of
 fitness, SMR, and body mass, allowing traits specific covariates to be
 accommodated within a single model. In males, linear selection
 differentials for mass and SMR were positive and individually significant.
 Selection gradients were also positive but, despite substantial sample
 sizes, were non-significant due to increased uncertainty given strong
 SMR-mass collinearity. In females, only nonlinear selection was detected
 and it appeared to act primarily on body size, although the individual
 gradients were again non-significant. Selection did not differ
 significantly between sexes although differences in the fitness surfaces
 suggest sex-specific selection as an important topic for further study.
description: Methods are described in Videlier, M., V. Careau, A.J. Wilson,
 and H.D. Rundle. Quantifying selection on standard metabolic rate and body
 mass in <em>Drosophila melanogaster</em>. Evolution: in
 press.
description: Each row corresponds to an individual fly (total: 1060
 individuals, 532 females and 528 males). Columns are as follows:
 BLOCK: Experimental block, a categorical variable with six levels
 (1 to 6) corresponding to the 6 temporal blocks over which the experiment
 was performed.<br> Sspop: Day of adult emergence, a categorical
 variable with three levels (1 to 3) corresponding to flies that ecolosed
 8, 9 or 10 days after eggs were laid.<br> B_S: A combination of
 block (six levels) and day of emergence (three levels).<br> ID: A
 categorical variable corresponding to a unique individual
 identifier.<br> SEX: A categorical variable with 2 levels (0 for
 female, 1 for male).<br> MASS: A continuous variable representing
 the wet body mass (g) of the individual.<br> TEMP: A continuous
 variable consisting of the average temperature (Celcius) during the 20 sec
 measurement of standard metabolic rate (i.e. SMR).<br> WV: A
 continuous variable representing the average water vapor  (ppt) during the
 20 sec SMR measurement.<br> LUX: A continuous variable representing
 the average light intensity (Lux) during the 20 sec SMR
 measurement.<br> FRC: A continuous variable representing the average
 flow rate (ml/min) during the 20 sec SMR measurement.<br> ACT20: A
 continuous variable representing the average locomotor activity during the
 20 sec SMR measurement.<br> ACT20p: A continuous variable
 representing the average locomotor activity 20 sec before SMR
 measurement.<br> SMR: A continuous variable representing the
 standard metabolic rate (ml CO2/min) of the individual.<br> MW_WTnb:
 Total number of wild-type offspring produced by the focal male; a
 continuous variable.<br> NbFemTot: A continuous variable
 representing the number of mutant (bw) females which were used for male
 fitness measurement.<br> FW_W: Total number of wild-type offspring
 produced by the focal female; a continuous variable.