Maternally-transferred thyroid hormones and life-history variation in birds
Hsu, Bin-Yan Hsu et al. (2022), Maternally-transferred thyroid hormones and life-history variation in birds, Dryad, Dataset, https://doi.org/10.5061/dryad.547d7wmb5
1. In vertebrates, thyroid hormones (THs) play an important role in the regulation of growth, development, metabolism, photoperiodic responses and migration. Maternally transferred THs are important for normal early-phase embryonic development when embryos are not able to produce endogenous THs. Previous studies have shown that variation in maternal THs within the physiological range can influence offspring phenotype.
2. Given the essential functions of maternal THs in development and metabolism, THs may be a mediator of life-history variation across species.
3. We tested the hypothesis that differences in life histories are associated with differences in maternal TH transfer across species. Using birds as a model, we specifically tested whether maternally transferred yolk THs co-vary with migratory status, developmental mode, and traits related to pace-of-life (e.g. basal metabolic rate, maximum lifespan).
4. We collected un-incubated eggs (n = 1-21 eggs per species, median = 7) from 34 wild and captive bird species across 17 families and 6 orders to measure yolk THs (both triiodothyronine, T3 and thyroxine, T4), compiled life-history trait data from the literature, and used Bayesian phylogenetic mixed models to test our hypotheses.
5. Our models indicated that both concentrations and total amounts of the two main forms of THs (T3 and T4) were higher in the eggs of migratory species compared to resident species, and total amounts were higher in the eggs of precocial species, which have longer prenatal developmental periods, than in those of altricial species. However, maternal yolk THs did not show clear associations with pace-of-life related traits, such as fecundity, basal metabolic rate, or maximum lifespan.
6. We quantified interspecific variation in maternal yolk THs in birds and our findings suggest higher maternal TH transfer is associated with the precocial mode of development and migratory status. Whether maternal THs represent a part of the mechanism underlying the evolution of precocial development and migration or a consequence of such life histories is currently unclear. We therefore encourage further studies to explore the physiological mechanisms and evolutionary processes underlying these patterns.
The study includes two data sets: yolk thyroid hormones ("egg_data_final.csv") and life-history traits ("life_histories.csv").
Yolk thyroid hormones were extracted and measured by a nano-liquid chromatography tandem mass spectrometry protocol from eggs of 34 bird species. Life-history traits were collected and compiled from literature at the species level.
The data package contains four parts:
Part I. data sets
Two data sets are included in this study:
egg_data.csv: Data set of yolk thyroid hormones measured in eggs of 34 bird species
life_histories.csv: life-history trait values used in the study, collected and compiled from the literature
info_eggdata.txt: information of variables (i.e. all columns) in egg_data.csv
info_lifehistories.txt: information of variables (i.e. all columns) in life_histories.csv
Part II. phylogeny
full_Ericon and full_Hackett: For the 34 species included in this study, 100 possible phylogenetic trees were obtained from two phylogenetic backbones via BirdTree.org.
Others are the subsets according to data availability. For details see the paper and its supplementary materials.
Part III. model results
Our statistical models were run across 100 possible trees from the two backbones. The final estimates were collected and stored in these files for each model.
Part IV. R codes
All R codes used to produce our results are provided.
data_process_final.R: code to process data before model fitting
mls_size_corrected.R: code to run size correction on maximum lifespan
aafr_size_corrected.R: code to run size correction on age at sexual maturity
bmr_size_corrected.R: code to run size correction on mass-specific BMR
k_size_corrected.R: code to run size correction on the logistic growth rate constant k
models_final.R: code that runs the Bayesian phylogenetic mixed models
results_final: code that reads, checks and collects results from the Bayesian phylogenetic mixed models
phylogenetic_heritability.R: code that calculate phylogenetic heritability associated with our models and results
model_diagnostics_final.R: code to examine model performance
ggplot theme setting 2020.R: code that sets up the ggplot2 environment to produce the paper figures
summarySE: a small function to calculate means, SE, etc. for graphic purposes
phylogeny graph.R: code that produces Fig. 1A
graphs from raw data.R: code that produces Fig. 1B-E, 3, and 4B-E in the paper
graphs from model results.R: code that produces Fig. 2 and 4A in the paper
Academy of Finland, Award: 286278