Seasonal adaptation: Geographic photoperiod-temperature patterns explain
genetic variation in the common vole Tsh receptor
Abstract
The vertebrate photoperiodic neuroendocrine system uses photoperiod as a
proxy to time annual rhythms in reproduction. To investigate seasonal
adaptation in mammals, the hinge region and the first part of the
transmembrane domain of the Tshr gene were sequenced for 278
common vole (Microtus arvalis) specimens from 15 localities in
Western Europe, and 28 localities in Eastern Europe. Forty-nine single
nucleotide polymorphisms (SNPs; 22 intronic, 27 exonic) were found, with
weak or zero correlation with pairwise geographical distance, latitude,
longitude and altitude. By applying a temperature threshold to the local
photoperiod-temperature ellipsoid, we obtained a predicted critical
photoperiod (pCPP) as a proxy for spring onset of local primary food
production (grass). The pCPP obtained explains the distribution of
genetic variation in Tshr in Western Europe through highly
significant correlations. Thus, Tshr, which plays a pivotal role
in the sensitivity of the mammalian photoperiodic neuroendocrine system,
was targeted by natural selection, resulting in optimized timing of
seasonal reproduction.