DOI: 10.5061/dryad.554t595
title: Data from: Migratory strategy explains differences in timing of female reproductive development in seasonally sympatric songbirds

description: 1. Divergent migratory strategies among populations can result in
 population-level differences in timing of reproduction (allochrony) and
 local adaptation. However, the mechanisms underlying among-population
 variation in timing are insufficiently understood, particularly in
 females. 2. We studied differences in reproductive development and its
 related mechanisms along the hypothalamic-pituitary-gonadal axis (HPG) in
 closely related migratory and sedentary (i.e., resident) female dark-eyed
 juncos (Junco hyemalis) living together in sympatry during early spring.
 Despite exposure to the same environmental cues in early spring, residents
 initiate breeding prior to the departure of migrants for their breeding
 grounds. We investigated whether residents would be more reproductively
 developed than migrants based on their behavioral differences.
 Alternatively, females could exhibit similar reproductive development in
 response to the same environmental cues despite differences in migratory
 behavior. To compare their degree of reproductive development during
 seasonal sympatry and the underlying mechanisms of these differences, we
 collected ovarian and liver tissue in early spring prior to migration, and
 compared transcript abundance of genes associated with reproduction using
 quantitative PCR. We also used stable hydrogen isotopes to infer relative
 breeding and wintering latitude of migrants. 3. We found higher transcript
 abundance of luteinizing hormone receptor and aromatase in the ovary in
 addition to significantly heavier ovaries in residents than in migrants.
 Together these results suggest greater sensitivity and response to
 upstream endocrine stimulation in resident females. Transcript abundance
 for other receptors in the ovary and liver associated with reproduction,
 however, did not differ between populations. When comparing ovarian
 development within migrants, females with lower hydrogen isotopes
 (indicating higher breeding latitudes) had smaller ovaries, suggesting
 that longer-distance migrations may further delay reproductive
 development. 4. Based on differences in ovary mass and transcript
 abundance, we conclude that females that differ in migratory strategy also
 differ in timing of reproductive development. These results support that
 divergent migratory behavior drives allochrony and could enable
 reproductive isolation between populations; mechanistic differences at the
 level of gonadal stimulation can explain these differences in timing of
 reproductive development.
description: Kimmittetal-OvarianReceptorData-publishedThis data file contains ovary mass, hydrogen isotopes, and gene expression data for the publication. SampleNo = Randomly assigned ovary sample number; FemaleID= Assigned female ID at time of euthanasia; Trig= Triglyceride levels (Indicator of Very-low density lipoprotein; VLDL; μg/μL); FeatherdD= Feather δ2H isotopes; ClawdD= Claw δ2H isotopes; Subspecies= Female migratory strategy; Date= Calendar date of capture of female individual; CaptureJulian= Julian date of capture of female individual; OvaryMass= Mass of ovary tissue (mg); Body Mass = Mass of body (without blood; g); NormLHR= Normalized transcript abundance of Luteinizing hormone receptor (LHR); NormFSHR= Normalized transcript abundance of Follicle-stimulating hormone receptor (FSHR); NormGR= Normalized transcript abundance of Glucocorticoid receptor (GR); NormMR= Normalized transcript abundance of Mineralocorticoid receptor (MR); NormGnIHR= Normalized transcript abundance of Gonadotropin-inhibitory hormone receptor (GnIHR); NormAROM= Normalized transcript abundance of aromatase (AROM)Kimmittetal-LiverReceptorData-publishedThis data file contains liver receptor gene expression data (mRNA transcript abundance) for this manuscript. SampleNo = Randomly assigned ovary sample number; FemaleID= Assigned female ID at time of euthanasia; Date= Calendar date of capture of female individual; CaptureJulian= Julian date of capture of female individual; Subspecies= Female migratory strategy; NormER= Normalized transcript abundance of Estrogen receptor (GR); NormGR= Normalized transcript abundance of Glucocorticoid receptor (GR); NormMR= Normalized transcript abundance of Mineralocorticoid receptor (MR)