Between- and within-individual variation of maternal thyroid hormone deposition in wild great tits (Parus major)

TY - JOUR

T1 - Between- and within-individual variation of maternal thyroid hormone deposition in wild great tits (Parus major)

AU - Hsu, Bin-Yan

AU - Verhagen, Irene C.

AU - Gienapp, P.

AU - Darras, Veerle M.

AU - Visser, M.E.

AU - Ruuskanen, S.

N1 - 6727, AnE; Data Archiving: data archived at Dryad

PY - 2019

Y1 - 2019

N2 - Maternal hormones are often considered a mediator of anticipatory maternal effects, namely mothers adjust maternal hormone transfer to prepare the offspring for the anticipated environment. The flexibility for mothers to adjust hormone transfer is therefore a prerequisite for such anticipatory maternal effects. Nevertheless, previous studies only focused on the average differences of maternal hormone transfer between groups and neglected the substantial individual variation, despite that individual plasticity on maternal hormone transfer is actually the central assumption. In this study, we studied the between- and within-individual variation of maternal thyroid hormones (THs) in egg yolk of wild great tits (Parus major) and estimated the individual plasticity of maternal yolk THs across environmental temperature, clutch initiation dates and egg laying order using linear mixed-effects models. Interestingly, our models provide statistical evidence that the two main THs – the main biologically active hormone T3, and the prohormone T4 – exhibited different variation patterns. Yolk T3 showed significant between-individual variation on the average levels, in line with its previously reported moderate heritability. Yolk T4, however, showed significant between-clutch variation in the pattern over the laying sequence, suggesting a great within-individual plasticity. Our findings suggest that the role and function of the hormone (pro vs active hormone) within the endocrine axis likely influences its flexibility to respond to environmental change. Whether the flexibility of T4 deposition brings fitness advantage should be examined along with its potential effects on offspring, which remains to be further investigated.

AB - Maternal hormones are often considered a mediator of anticipatory maternal effects, namely mothers adjust maternal hormone transfer to prepare the offspring for the anticipated environment. The flexibility for mothers to adjust hormone transfer is therefore a prerequisite for such anticipatory maternal effects. Nevertheless, previous studies only focused on the average differences of maternal hormone transfer between groups and neglected the substantial individual variation, despite that individual plasticity on maternal hormone transfer is actually the central assumption. In this study, we studied the between- and within-individual variation of maternal thyroid hormones (THs) in egg yolk of wild great tits (Parus major) and estimated the individual plasticity of maternal yolk THs across environmental temperature, clutch initiation dates and egg laying order using linear mixed-effects models. Interestingly, our models provide statistical evidence that the two main THs – the main biologically active hormone T3, and the prohormone T4 – exhibited different variation patterns. Yolk T3 showed significant between-individual variation on the average levels, in line with its previously reported moderate heritability. Yolk T4, however, showed significant between-clutch variation in the pattern over the laying sequence, suggesting a great within-individual plasticity. Our findings suggest that the role and function of the hormone (pro vs active hormone) within the endocrine axis likely influences its flexibility to respond to environmental change. Whether the flexibility of T4 deposition brings fitness advantage should be examined along with its potential effects on offspring, which remains to be further investigated.

KW - international

KW - great tits

KW - thyroid hormones

KW - individual variation

KW - multilevel linear mixed model

KW - maternal hormones

KW - reaction norms

UR - https://doi.org/10.5061/dryad.kp524f5

U2 - 10.1086/704738

DO - 10.1086/704738

M3 - Article

SN - 0003-0147

VL - 194

SP - E96-E108

JO - American Naturalist

JF - American Naturalist

IS - 4

ER -