The Relationships Between Gene Variations and Climate in Two Bird Species Breeding in Anatolia

Abstract

CLOCK protein is encoded by the Clock gene in a negative feedback loop which regulates the circadian clock in response to environmental stimuli by functioning as a transcription activator. Glutamine repeat variations are found at the C-terminus of the product of this gene. The other gene, Adcyap1, expressed in vertebrates encodes pituitary adenylate cyclase-activating polypeptide (PACAP). This product has several impacts on physiological and behavioral characters. Studies have revealed simple sequence repeat variation in the 3’ non-translational region of the Adcyap1 gene, possibly leading to RNA transcript modifications. Studies based on the effects of these candidate genes on life history phenologies show that different allelic variations are associated with circadian rhythm-related characters such as feather change, dispersal timing and distance, migration timing, migration restlessness, migration distance, migration status, clutch size, incubation duration, laying and hatching date, and breeding latitude. However, further studies are needed to reveal the extent to which the Clock and Adcyap1 genes constitute the genetic basis of these phenologies.

In this thesis, the geographic structure of the Clock and Adcyap1 polymorphisms in the common chaffinch (Fringilla coelebs) and the European greenfinch (Chloris chloris) populations was tried to be discovered by calculating fixation indices and using analysis of molecular variance, principal component analysis, and STRUCTURE software. In addition, associations of bioclimatic variables (e.g., seasonality of temperature, precipitation, and climate heterogeneity), spatial variables (e.g., latitude, longitude, and altitude), and morphological characters (e.g., wing and body length) with allele lengths were investigated by linear models in chaffinch and greenfinch species.

As a result, no population differentiation was found for these 2 finch species. However, especially the Adcyap gene showed remarkable relationships with bioclimatic variables. According to linear models, the distribution of chaffinch alleles was positively correlated with climate heterogeneity and temperature seasonality, as hypothesized above. Similarly, Clock allele length of chaffinch was correlated with longitude. Positive associations were also found between the migration-related morphological characters, primary, tail, and body length, and Adcyap1 length in both species. The combined results suggest that the minimum allele lengths might show dominant effects for both gene regions. Finally, it was observed that the heterozygosity of greenfinch populations was associated with the mean Clock gene length.