Understanding how dispersal impacts the genetic makeup of populations is essential for predicting their responses to environmental change. Gene flow—via within‐population dispersal and external immigration—shapes population health and evolutionary potential by boosting genetic diversity, but it can also counteract local adaptation. We investigate these processes in a population of great tits ( Parus major ) in Wytham Woods, Un...

Understanding speciation is a fundamental goal in evolutionary biology. Genome scans of genetic differentiation ( F ST ) have become a cornerstone of speciation research, helping identify genomic regions likely involved in population divergence and speciation. While such studies have advanced our understanding, the relationship between epigenetic mechanisms and genetic differentiation remains unclear. Here, we present evidence...

The formation of new species often involves the correlated divergence of multiple traits and genetic regions. However, the mechanisms by which such trait covariation builds up remain poorly understood. In this context, we consider two non‐exclusive hypotheses. First, genetic covariance between traits can cause divergent selection on one trait to promote population divergence in correlated traits (a genetic covariation hypothes...

Migratory birds are inherently vagile, a strategy that may reduce the impacts of habitat loss and fragmentation on genetic diversity. However, specialist resource requirements and range‐edge distribution can counteract these benefits. The European nightjar ( Caprimulgus europaeus ) is a long‐distance migratory bird and resource specialist. Like other long‐distance migrants, nightjar populations have declined across the British...

Epigenetic mechanisms, such as DNA methylation, can influence gene regulation and affect phenotypic variation, raising the possibility that they contribute to ecological adaptation. Beginning to address this issue requires high‐resolution sequencing studies of natural populations to pinpoint epigenetic regions of potential ecological and evolutionary significance. However, such studies are still relatively uncommon, especially...

Genomic prediction, the technique whereby an individual's genetic component of their phenotype is estimated from its genome, has revolutionised animal and plant breeding and medical genetics. However, despite being first introduced nearly two decades ago, it has hardly been adopted by the evolutionary genetics community studying wild organisms. Here, genomic prediction is performed on eight traits in a wild population of Soay...

Social interactions are rarely random. In some instances, animals exhibit homophily or heterophily, the tendency to interact with similar or dissimilar conspecifics, respectively. Genetic homophily and heterophily influence the evolutionary dynamics of populations, because they potentially affect sexual and social selection. Here, we investigate the link between social interactions and allele frequencies in foraging flocks of...

The genetic architecture of a trait usually refers to the number and magnitude of loci that explain phenotypic variation. A description of genetic architecture can help us to understand how genetic variation is maintained, how traits have evolved and how phenotypes might respond to selection. However, linkage mapping and association studies can suffer from problems of bias, especially when conducted in natural populations wher...

Currently, there is much debate on the genetic architecture of quantitative traits in wild populations. Is trait variation influenced by many genes of small effect or by a few genes of major effect? Where is additive genetic variation located in the genome? Do the same loci cause similar phenotypic variation in different populations? Great tits ( Parus major ) have been studied extensively in long‐term studies across Europe an...

Seasonally changing environments at high latitudes present great challenges for the reproduction and survival of insects, and photoperiodic cues play an important role in helping them to synchronize their life cycle with prevalent and forthcoming conditions. We have mapped quantitative trait loci ( QTL ) responsible for the photoperiodic regulation of four life history traits, female reproductive diapause, cold tolerance, egg‐...

When domesticated species are not reproductively isolated from their wild relatives, the opportunity arises for artificially selected variants to be re‐introduced into the wild. However, the evolutionary consequences of introgression of domesticated genes back into the wild are poorly understood. By combining high‐throughput genotyping with 25 years of long‐term ecological field data, we describe the occurrence and consequence...

The underlying basis of genetic variation in quantitative traits, in terms of the number of causal variants and the size of their effects, is largely unknown in natural populations. The expectation is that complex quantitative trait variation is attributable to many, possibly interacting, causal variants, whose effects may depend upon the sex, age and the environment in which they are expressed. A recently developed methodolog...

Clutch size and egg mass are life history traits that have been extensively studied in wild bird populations, as life history theory predicts a negative trade‐off between them, either at the phenotypic or at the genetic level. Here, we analyse the genomic architecture of these heritable traits in a wild great tit ( Parus major ) population, using three marker‐based approaches – chromosome partitioning, quantitative trait locus...

The discipline of molecular ecology has undergone enormous changes since the journal bearing its name was launched approximately two decades ago. The field has seen great strides in analytical methods development, made groundbreaking discoveries and experienced a revolution in genotyping technology. Here, we provide brief perspectives on the main subdisciplines of molecular ecology, describe key questions and goals, discuss co...

Inbreeding is common in small and threatened populations and often has a negative effect on individual fitness and genetic diversity. Thus, inbreeding can be an important factor affecting the persistence of small populations. In this study, we investigated the effects of inbreeding on fitness in a small, wild population of house sparrows ( Passer domesticus ) on the island of Aldra, Norway. The population was founded in 1998 b...

The ecological and evolutionary importance of fine‐scale genetic structure within populations is increasingly appreciated. However, available data are largely restricted to wild vertebrates and eusocial insects. In addition, there is the expectation that most insects tend to have such large‐ and high‐density populations and are so mobile that they are unlikely to face inbreeding risks through fine‐scale population structuring....

Understanding the genetic architecture of phenotypic variation in natural populations is a fundamental goal of evolutionary genetics. Wild Soay sheep ( Ovis aries ) have an inherited polymorphism for horn morphology in both sexes, controlled by a single autosomal locus, Horns . The majority of males have large normal horns, but a small number have vestigial, deformed horns, known as scurs; females have either normal horns, scu...

In recent years there has been a dramatic increase in the availability of high density genetic marker data for both model and non‐model organisms. A potential application of these data is to infer relatedness in the absence of a complete pedigree. Using a marker panel of 771 SNPs genotyped in three generations of an extensive zebra finch pedigree, correlations between pedigree relatedness and seven marker‐based estimates of re...

A key question for molecular and behavioural ecologists who study mating systems is to understand why, in many species, females choose to mate with extra‐pair males. Recently a possible explanation, ‘genetic compatibility’, has gained increasing empirical support (for a comprehensive review, see Kempenaers 2007 ). Genetic compatibility hypotheses assume that females seek extra‐pair mates with alleles that complement their own....

We present a predicted passerine genome map consisting of 196 microsatellite markers distributed across 25 chromosomes. The map was constructed by assigning chromosomal locations based on the sequence similarity between 550 publicly available passerine microsatellites and the draft chicken genome sequence published by the International Chicken Genome Sequencing Consortium. We compared this passerine microsatellite map with a r...