Individual variation among and within natural populations can have eco‐evolutionary implications by, for example, affecting species interactions or evolutionary potential. Urban systems present a unique opportunity to evaluate how environmental change shapes variation since urban phenotypic differentiation is widely documented on contemporary timescales. We introduce and test three hypotheses to determine how urbanisation affe...

Variation in age structure influences population dynamics, yet we have limited understanding of the spatial scale at which its fluctuations are synchronised between populations. Using 32 great tit populations, spanning 4° W–33° E and 35°–65° N involving > 130,000 birds across 67 years, we quantify spatial synchrony in breeding demographic structure (subadult vs. adult breeders) and its drivers. We show that larger clutch sizes...

Identifying the environmental drivers of variation in fitness‐related traits is a central objective in ecology and evolutionary biology. Temporal fluctuations of these environmental drivers are often synchronized at large spatial scales. Yet, whether synchronous environmental conditions can generate spatial synchrony in fitness‐related trait values (i.e., correlated temporal trait fluctuations across populations) is poorly und...

Conservation actions often focus on restoration or creation of natural areas designed to facilitate the movements of organisms among populations. To be efficient, these actions need to be based on reliable estimates or predictions of landscape connectivity. While circuit theory and least‐cost paths (LCPs) are increasingly being used to estimate connectivity, these methods also have proven limitations. We compared their perform...

The impact of demographic parameters on the genetic population structure and viability of organisms is a long‐standing issue in the study of fragmented populations. Demographic and genetic tools are now readily available to estimate census and effective population sizes and migration and gene flow rates with increasing precision. Here we analysed the demography and genetic population structure over a recent 15‐year time span i...

Although relatedness between mates is of considerable evolutionary and ecological significance, the way in which the level of relatedness is determined by different behavioural processes remains largely unknown. We investigated the role of behaviour in predicting mate relatedness in great tits using genotypic markers and detailed observations. We studied how mate relatedness is influenced by natal dispersal, inbreeding/outbree...

Red squirrels ( Sciurus vulgaris ) are widely distributed throughout Eurasia, occurring in many types of coniferous and mixed‐deciduous forests. In fragmented landscapes, small and partly isolated populations with low immigration rates show reduced genetic diversity, but reforestation can increase gene flow and restore levels of genetic variation in a few decades. No studies have so far investigated the genetic structure of re...

Studies of inbreeding depression or kin selection require knowledge of relatedness between individuals. If pedigree information is lacking, one has to rely on genotypic information to infer relatedness. In this study we investigated the performance (absolute and relative) of 10 marker‐based relatedness estimators using allele frequencies at microsatellite loci obtained from natural populations of two bird species and one mamma...