DOI: 10.5061/dryad.n8pk0p38m
title: Data from: Mitochondrial function predicts dominance status in brown trout

description: In social hierarchies, winning contests confers better access to food,
 shelter, and reproductive opportunities. Clear dominance relationships are
 often apparent even when opponents are matched for experience, age, size,
 and other obvious characteristics. One explanation for this could be
 among-individual differences in mitochondrial function, since this could
 be associated with the cellular allocation of energy to
 dominance-associated traits. Here, we tested whether the dominance status
 of juvenile brown trout (Salmo trutta) was related to their mitochondrial
 function. We determined each fish’s dominance status by staging a series
 of contests for a feeding territory in an artificial stream tank;
 observations of colouration, food acquisition, and aggressive behaviour
 allowed the assignment of dominance. Mitochondrial function (the capacity
 for ATP production, and the efficiency with which ATP is produced) was
 then measured in the muscles used for swimming, analysed at the level of
 both homogenised tissue and isolated mitochondria. We found that a fish’s
 net phosphorylation efficiency (i.e., the efficiency with which ATP is
 produced) was a significant predictor of its dominance-associated
 colouration and the level of aggression it exhibited towards an opponent.
 However, a fish’s overall dominance status was instead predicted by its
 capacity for oxidative phosphorylation (i.e. ATP production capacity).
 Moreover, oxidative phosphorylation was also a significant predictor of
 whether a fish would be categorised as being subordinate or dominant in a
 binary classification. While it is now well established that
 organism-level metabolism is a fundamental trait linking an individual’s
 ecology, physiology and life history, it is only relatively recently that
 the causes of among-individual variation in this trait have been
 investigated, with a shift in focus towards the ways in which energy is
 produced at a cellular level. By showing that mitochondrial function is
 related to competitive ability, this study exemplifies how cellular energy
 production can influence contest outcomes and thus the architecture of
 social hierarchies.
description: # Data from: Mitochondrial function predicts dominance status in brown
 trout
 [https://doi.org/10.5061/dryad.n8pk0p38m](https://doi.org/10.5061/dryad.n8pk0p38m) This dataset was collected and analysed by the authors of the paper “Mitochondrial function predicts dominance status in brown trout”, which is published in the journal Functional Ecology. Data_for_Dryad_-_McLennan_et_al._2025._Functional_Ecology.xlsx ## Description of the data and file structure: Please see below for an overview of each variable: * Fish ID ~ This is the unique ID that we assigned to each of the trout. * Tag ~ Each of the four fish within a cohort had a unique VIE tag (i.e., one yellow, one red, one green and one white). * Cohort ~ The experimental cohort that each fish belonged to. * Colouration score ~ Fish were assigned a score at each observation period, depending on whether they were relatively brighter (indicating dominance) or darker (indicating subordination). Range = -24 to 24. * Food capture score ~ The number of food items that were captured by an individual in relation to the number of food items that were captured overall. Expressed as a percentage. Range = 0 to 100. * Aggression score ~ Fish were assigned a score at each observation period, depending on the number of agnostic interactions between the two individuals and whether they were the initiator or recipient. Range = -152 to 312. * Dominance score ~ The first three scores were summarised into one latent variable using principal components analysis, thus assigning each individual an overall dominance score. Range = -2.38 to 2.27. * Dominance rank ~ Each individual was categorised as either subordinate (individuals with a PC1 score below 0) or dominant (individuals above 0). * Sex ~ Individuals were assigned as male or female using a conventional PCR sexing assay. * Fork length ~ The length of each individual measured to the nearest 1mm, from the most anterior point of the head to the fork of the tail. Measured the day prior to entering the trials. Range = 46.7 to 53.7. * Mito level OXPHOS ~ The oxygen consumption rate during oxidative phosphorylation per µg of protein from isolated mitochondria. This oxygen consumption rate was measured in the presence of all substrates (pyruvate, malate, glutamate and succinate) and saturating levels of ADP. Measured as pmol O2.s-1.ug-1. Range = 0.48 to 2.22. * Mito level OxCE ~ A measure of mitochondrial oxygen consumption efficiency for isolated mitochondria. OXPHOS Coupling Efficiency (OxCE) is a standardisation between 0 and 1 of the respiratory control ratio (RCR; ratio of OXPHOS to Leak respiration after addition of oligomycin). OxCE = 1 – (1/RCR). Unitless. Range = 0.75 to 0.92. * Tissue level OXPHOS ~ The maximum oxygen consumption rate per mg of wet weight shredded tissue preparation. This oxygen consumption rate was measured in the presence of all substrates (pyruvate, malate, glutamate and succinate) and saturating levels of ADP. Measured as pmol.s-1.mg-1. Range = 3.81 to 13.50. It was not possible to measure tissue level mitochondrial traits in one of the cohorts due to a technical failure, therefore n = 44 for this variable. * Tissue level OxCE ~ A measure of mitochondrial oxygen consumption efficiency for the shredded tissue preparation. OXPHOS Coupling Efficiency (OxCE) is a standardisation between 0 and 1 of the respiratory control ratio (RCR; ratio of OXPHOS over the Leak respiration after addition of oligomycin). OxCE = 1 – (1/RCR). Unitless. Range = 0.78 to 0.93. It was not possible to measure tissue level mitochondrial traits in one of the cohorts due to a technical failure, therefore n = 44 for this variable. * Oxygraph chamber ~ The Oxygraph-2k chamber (out of four) that was used to measure an individual's mitochondrial physiology. * CS ~ The rate of Citrate Synthase activity. Used as a quantitative proxy of mitochondrial volume. Measured as umol.g-1.min-1. Range = 5.85 to 12.54. It was not possible to measure tissue level mitochondrial traits in one of the cohorts due to a technical failure, therefore n = 44 for this variable. * Tissue level OXPHOS/CS ~ The oxygen consumption rate during oxidative phosphorylation per mg of wet weight shredded tissue preparation, divided by CS activity in the same tissue. This oxygen consumption rate was measured in the presence of all substrates (pyruvate, malate, glutamate and succinate) and saturating levels of ADP. Measured as nmol O2/µmol. Range = 0.36 to 2.00. It was not possible to measure tissue level mitochondrial traits in one of the cohorts due to a technical failure, therefore n = 44 for this variable.