Clock gene is associated with individual variation in the activation of reproductive endocrine and behavior of Asian short toed lark

Shuping Zhang,Xianglong Xu,Weiwei Wang,Wei Liang,Wenyu Yang

doi:10.1038/s41598-017-15064-7

Shuping Zhang, Xianglong Xu + Show 3 more

Open Access

https://doi.org/10.1038/s41598-017-15064-7

Copy DOI

Abstract

Within year individual variation in the timing of seasonal reproduction within wild bird populations in highly seasonal environments can be pronounced, but the molecular and physiological mechanisms responsible for this variation are unclear. We investigated the relationship between Clock gene poly-Q length, activation of the HPG endocrine axis, and the timing of breeding behavior, in a wild population of the Asian short-toed lark (Calandrella cheleensis) in Inner Mongolia, China. Six variants of Clock gene poly-Q alleles were identified in this population. Clock poly-Q mean allele length was positively correlated with the mean peak date deviation of individual birds. The shorter an individual’s Clock poly-Q mean allele length, the earlier its plasma LH, T and E2 values peaked. Mean Clock poly-Q allele length of nestlings in the same nest were positively correlated with the standardized laying date of the first egg in that nest. These results suggest that the Clock gene influences the reproductive timing of birds through its effect on the HPG endocrine axis, and that individual variation in the timing of reproduction may have a genetic basis.

Highlights

Seasonal timing of breeding is a nearly ubiquitous feature of birds in mid to high latitude areas
In this paper we present data on the relationship between Clock gene poly-Q length, the activation of hypothalamus –pituitary-gonad (HPG) endocrine axis, and the timing of breeding behavior in a wild population of the Asian short-toed lark (Calandrella cheleensis, Passeriformes, Alaudidae) in Inner Mongolia, China, a population that displays significant within year individual variation in the timing of breeding behavior[36]
The results of Linear Mixed Model (LMM) indicate that of the explanatory variables ClkpolyQ length, body mass, sex and year, only ClkpolyQ length had a significant effect on plasma luteinizing hormone (LH), T and E2 Peak date Deviation (PD; see Methods for definition) values (Table 2)

Summary

Introduction

Seasonal timing of breeding is a nearly ubiquitous feature of birds in mid to high latitude areas. Previous research conducted by us on this population indicates that it only breeds once a year, and that there is considerable variation between pairs in the dates on which the first eggs are laid and the first chicks are hatched; the earliest and latest laying and hatching dates are about 15 days apart[37] This species is very suitable for exploring the genetic basis of individual variation in the timing of breeding behavior. Based on evidence from blue tits and barn swallows[23,26], we hypothesized that individuals with longer Clock gene alleles initiate the HPG endocrine axis later, and breed later than those with shorter Clock gene alleles To test this hypothesis, we investigated the relationship between the secretion rate of plasma LH, T (males only), E2 (females only) and Clock gene poly-Q region length, in wild-caught birds housed in field aviaries at the study site in the spring of each year between 2014 and 2016. In this part of the study we inferred mean ClkpolyQ allele length of two parents from mean allele length of all their nestlings because breeding adults were difficult to catch, and because the mean allele length of parents would be expected to be equal to the mean allele length of all their offspring

Objectives

Methods

Results

Conclusion