Time trees and Clock genes: a Systematic Review and Comparative Analysis of contemporary Avian Migration Genetics

Louis Stéphane IV Le Clercq, G Bazzi, J.G. Cecere, L. Gianfranceschi, J. Paul Grobler, Antoinette Kotze, D Rubolini, M Liedvogel, Desire Lee Dalton

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Timing is a crucial aspect for survival and reproduction in seasonal environments
leading to carefully scheduled annual programs of migration in many species. The exact mechanisms through which birds (class: Aves [Linnaeus, 1758]) can keep track of time, anticipate seasonal changes, and adapt their behaviour, has become a subject of inquiry. One proposed mechanism regulating annual behaviour is the circadian clock, controlled by a highly conserved set of genes, collectively called “clock genes” which are well established in controlling the daily rhythmicity of physiology and behaviour. Due to diverse migration patterns observed within and between species, in a seemingly endogenously programmed manner, the field of migration genetics has sought and tested several candidate genes within the clock circuitry that may portend the observed differences in breeding and migration behaviour. Among others, length polymorphisms within genes such as the Clock and Adcyap1 have been hypothesised to play a putative role, though association and fitness studies in various species have yielded mixed results. To contextualize the existing body of data, here we conducted a systematic review of all published studies relating polymorphisms in clock genes to seasonality in a phylogenetically and taxonomically informed manner. This was
complemented by a standardised comparative re-analysis of candidate gene polymorphisms of 76 bird species, of which 58 are migrants and 18 are resident.
Genetic diversity estimates were assessed, Mantel tests performed, and Phylogenetic generalised least square models fitted to evaluate relationships between candidate gene allele length and population averages for geographic range, migration distance, timing of migration, taxonomic relationships, and divergence times. The combined meta-analysis provided evidence (i) of an association between Clock gene variation and Autumn migration as well as an association between Adcyap1 gene variation and Spring migration in migratory species, (ii) that these candidate genes are not diagnostic markers to distinguish migratory from sedentary birds, and (iii) of correlated variability in both genes to divergence time, potentially reflecting ancestrally inherited genotypes rather than contemporary changes driven by selection. These finding highlight a tentative association between candidate genes and migration attributes as well as genetic constraints to evolutionary adaptation.
Original languageEnglish
JournalBiological Reviews
Publication statusPublished - 8 Mar 2023


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