Although roads are widely seen as dispersal barriers, their genetic consequences for animals that experience large fluctuations in population density are poorly documented. We developed a spatially paired experimental design to assess the genetic impacts of roads on cyclic voles (Microtus arvalis) during a high-density phase in North-Western Spain. We compared genetic patterns from 15 paired plots bisected by three different barrier types, using linear mixed models and computing effect sizes to assess the importance of each type, and the influence of road features like width or the age of the infrastructure. Evidence of effects by roads on genetic diversity and differentiation were lacking. We speculate that the recurrent (each 3–5 generations) episodes of massive dispersal associated with population density peaks can homogenize populations and mitigate the possible genetic impact of landscape fragmentation by roads. This study highlights the importance of developing spatially replicated experimental designs that allow us to consider the large natural spatial variation in genetic parameters. More generally, these results contribute to our understanding of the not well explored effects of habitat fragmentation on dispersal in species showing “boom-bust” dynamics.

The common vole is one of the mammalian pests causing more agricultural damage in Europe. Since the late 1970s, this species has invaded the Duero valley in NW Spain, colonizing ca. 5 million ha of agricultural areas of the valley in about 20 years. Once settled in agricultural landscapes, the species experienced cyclic population outbreaks causing crop damages. The major vole population outbreak of 2006–2007 was managed by the Regional Government (Junta de Castilla y León, JCYL) mainly through large-scale application of anticoagulant rodenticides (ARs) and widespread destruction of field margins, natural vegetation patches, and crop stubbles by burning. These actions caused serious damage to regional agrarian biodiversity, including small game species. The coordinated action of scientific institutions and environmental NGOs, with the support of the main Spanish hunting association at a critical time, led to a progressive shift in pest management strategies during subsequent outbreaks, promoting the adoption of biological control and other management techniques causing less environmental damage. Finally, JCYL implemented an IPM program mainly based on biological control, good farming practices, and habitat management. This program has been increasingly adopted in recent years, leading to a marked reduction in chemical control and the complete elimination of burning as a tool of management. Over this period, the scientific knowledge of the species’ ecology has expanded substantially, providing key insights for the development and refinement of IPM strategies. Here, we synthesize this body of knowledge and provide additional recommendations to further improve the current IPM program, which may serve as a model for rodent pest management in other regions worldwide.

Natal dispersal is a key life history trait determining fitness and driving population dynamics, genetic structure, and species distributions. Despite existing evidence that not all phenotypes are equally likely to successfully establish in new areas, the mechanistic underpinnings of natal dispersal remain poorly understood. The propensity to disperse into a new environment can be favoured by a high degree of phenotypic plasticity, which facilitates local adaptation and may be achieved via epigenetic mechanisms, which modify gene expression and enable rapid phenotypic changes. Epigenetic processes occur in particular genomic regions—DNA methylation on CpG sites in vertebrates—and thus individual genomes may differ in their capacity to be modified epigenetically. This ‘Epigenetic potential’ (EP) may represent the range of phenotypic plasticity attainable by an individual and be a key determinant of successful settlement in novel areas. We investigated the association between EP—quantified as the number of genome‐wide CpG variants—and natal dispersal propensity in a long‐term study population of Pied flycatchers ( Ficedula hypoleuca ) monitored since colonisation of a new habitat 35 years ago. We tested this association at three levels, comparing EP between: (i) individuals dispersing between and within habitat patches; (ii) immigrants to the population and locally born individuals; and (iii) individuals from first (comprising colonisers or their direct descendants) and later generations of the population (consisting of locally born individuals, which did not show natal dispersal between habitat patches). Results show a significant, positive association between EP and dispersal propensity in comparisons (i)—only in females—and (iii), but not (ii). Furthermore, CpG variants were non‐randomly distributed across the genome, suggesting species‐ and/or population‐specific CpGs being more frequent in promoters and exons. Our findings point to EP playing a role in dispersal propensity at spatial and temporal scales, supporting the idea that epigenetically driven phenotypic plasticity facilitates dispersal and environmental coping in free‐living birds.