A framework for the study of genetic variation in migratory behaviour

Abstract

Evolutionary change results from selection acting on genetic variation. For migration to be successful, many different aspects of an animal's physiology and behaviour need to function in a co-coordinated way. Changes in one migratory trait are therefore likely to be accompanied by changes in other migratory and lifehistory traits. At present, we have some knowledge of the pressures that operate at the various stages of migration, but we know very little about the extent of genetic variation in various aspects of the migratory syndrome. As a consequence, our ability to predict which species is capable of what kind of evolutionary change, and at which rate, is limited. Here, we review how our evolutionary understanding of migration may benefit from taking a quantitative-genetic approach and present a framework for studying the causes of phenotypic variation. We review past research, that has mainly studied single migratory traits in captive birds, and discuss how this work could be extended to study genetic variation in the wild and to account for genetic correlations and correlated selection. In the future, reactionnorm approaches may become very important, as they allow the study of genetic and environmental effects on phenotypic expression within a single framework, as well as of their interactions. We advocate making more use of repeated measurements on single individuals to study the causes of among-individual variation in the wild, as they are easier to obtain than data on relatives and can provide valuable information for identifying and selecting traits. This approach will be particularly informative if it involves systematic testing of individuals under different environmental conditions. We propose extending this research agenda by using optimality models to predict levels of variation and covariation among traits and constraints. This may help us to select traits in which we might expect genetic variation, and to identify the most informative environmental axes. We also recommend an expansion of the passerine model, as this model does not apply to birds, like geese, where cultural transmission of spatio-temporal information is an important determinant of migration patterns and their variation.

Migratory decisions in birds: extent of genetic versus environmental control

“…However, we cannot assume that these responses will necessarily improve the probability of persistence without a better understanding of reaction norms for speciWc traits within individual species (van Noordwijk et al 2006). Furthermore, climate and land-use changes could adversely aVect migratory birds through decoupling of the proximate cues and ultimate processes that aVect migratory decisions (Coppack and Both 2002;Gienapp and Visser 2006).…”

Current selection for lower migratory activity will drive the evolution of residency in a migratory bird population

“…Common garden experiments allow us to draw inferences about genetic changes in wild populations if experimental conditions are strictly controlled and do not change over time (15,63). To achieve this, we collected nestlings at an early age, hand-raised them, and studied birds in climate-controlled chambers in captivity, which allowed us to follow a highly standardized protocol for rearing, keeping, and measuring birds throughout the complete study from 1988 through 2002.…”

Intra- and inter-individual variations in flight direction in a migratory butterfly co-vary with individual mobility

“…These syndromes rely on a suite of phenotypic traits that co-evolve to determine the behavioural types of individuals. Such syndromes have been extensively studied in the context of migration because migration implies selection on morphological characters for long distance movements (Van Noordwijk et al, 2006) resulting in different characteristics between migrant and resident individuals (Sandberg and Moore, 1996;Lõhmus et al, 2003;Marchetti and Zehtindjiev, 2009). For example, Leisler and Winkler showed that migrant birds are generally smaller and have shorter tails and longer wings than non-migrant individuals (Leisler and Winkler, 2003).…”