DOI: 10.5061/dryad.85950
title: Data from: No mutual mate choice for quality in zebra finches: time to question a widely-held assumption

description: Studies of mate choice typically assume that individuals prefer high
 quality mates and select them based on condition-dependent indicator
 traits. In species with bi-parental care, mutual mate choice is expected
 to result in assortative mating for quality. When assortment is not
 perfect, the lower quality pair members are expected to compensate by
 increased parental investment to secure their partner (positive
 differential allocation). This framework has been assumed to hold for
 monogamous species like the zebra finch (Taeniopygia guttata), but
 progress has been hampered by the difficulty to define individual quality.
 By combining multiple measures of causes (inbreeding, early nutrition) and
 consequences (ornaments, displays, fitness components) of variation in
 quality into a single principal component, we here show that quality
 variation can be quantified successfully. We further show that variation
 in quality indeed predicts individual pairing success, presumably because
 it reflects an individual's vigor or ability to invest in
 reproduction. However, despite high statistical power, we found no
 evidence for either assortative mating or for positive differential
 allocation. We suggest that zebra finch ornaments and displays are not
 sufficiently reliable for the benefits of choosiness to exceed the costs
 of competition for the putative best partner. To assess the generality of
 these findings unbiased quantification of signal honesty and preference
 strength is required, rather than selective reporting of significant
 results.
description: PCA of female zebra
 finches_table2PCA of 219 female zebra
 finches based on six traits: fecundity, mass day 8, mass day 100,
 inbreeding coefficient (Fshort), brood size and beak color
 (BC).PCA of male zebra
 finches_table2PCA of 217 male zebra
 finches based on 10 traits: siring success, Natal brood size, Mass day 8,
 Mass day 100, Inbreeding_coefficient (Fshort), Beak color(BC), Cheek patch
 size, Courtship rate(meanroot11), Repertoire size,
 Amplitude.Pearson r of 7
 traits_population wide_table3Test for assortative
 mating for various quality traits of males and females (seven traits)
 calculated at the population-wide. At the population level, sample size
 (n) indicates the number of pairs for which a Pearson correlation
 coefficient was calculated. ‘Fitness’ refers to the number of eggs laid
 (female fecundity) or fertilized (male siring success). PCA score refers
 to the estimate of overall quality (Table 2) based on the other breeding
 round, i.e. when not paired to the focal partner.Pearson r of 7
 traits_within aviary_table3Test for assortative
 mating for various quality traits of males and females calculated at the
 within-aviary level. At the aviary level, the sample size indicates the
 number of aviaries for which a Pearson correlation coefficient was
 calculated; shown are the mean correlation coefficients for each trait.
 ‘Fitness’ refers to the number of eggs laid (female fecundity) or
 fertilized (male siring success). PCA score refers to the estimate of
 overall quality (Table 2) based on the other breeding round, i.e. when not
 paired to the focal partner.Pearson r of Pairing
 status_table 4Test for assortative
 mating for male versus female estimates of quality (PCA scores, Table 2)
 across pairs of various status categories (all pair bonds observed, all
 exclusively monogamous relationships, the subset of monogamous
 relationships that lasted until the end of a breeding round, and all
 polygamous relationships).model testing the
 differential-allocation hypothesis_table5Data for the linear
 mixed-effect model testing the differential-allocation hypothesis based on
 observations of the proportion of female incubation in 283 out of 292
 lasting monogamous pairs that initiated breeding. The dependent variable
 is the relative count of female versus male nest visit (FIDInc and MIDinc)
 records (using the ‘cbind’ function in R) within each pair. The random
 effects male and female identity (ID) reflect the individual repeatability
 across different partners (variance component V), while the random effect
 pair ID controls for overdispersion in the binomial counts. The predictor
 of interest (quality difference) is the difference in estimated quality
 between the partners (female PCA score minus male PCA
 score:diff_FM).Pairing success ~
 quality_figure1Data for the Figure1:
 Pairing success of individuals as a function of their quality (scored as
 the first principal component reflecting the quality indicators given in
 Table 2).data for
 figure2Data for figure2:
 Principal component scores reflecting individual quality of males and
 females that formed a pair bond during the first and second breeding
 round. Note that PC scores are calculated from data of the other breeding
 round.pair status &
 quality_ FigS1Data for figureS1: PC
 scores of monogamous, polygamous and unpaired individuals of both sexes.
 Pairing status during the first breeding round in relation to the PC score
 from the second breeding round (PC1_other_round); Pairing status from the
 second round in relation to the PC score from the first round
 (PC1_other_round).pair status and quality_
 FigS2Data for FigS2:
 Principal component scores of mated pairs of different pairing status (as
 in Fig. 2, but both breeding rounds combined).dynamic assortment in
 aviary_FigS3Data for FigS3: Male and
 female quality (PC scores from the other breeding round) and level of
 assortative mating for PC scores (Pearson correlation coefficient r) in
 relation to the order of pairing within aviaries (AV). All pair bonds that
 were formed within an aviary were ranked by the order of pair formation
 (Pairing order within aviary).