Livestock Corridors Working as Pollinator Refuges and Dispersal Hotspots: Lessons from Spain

Habitat fragmentation is one of the greatest threats to biodiversity conservation and ecosystem productivity mediated by direct human impact. Its consequences include genetic depauperation, comprising phenomena such as inbreeding depression or reduction in genetic diversity. While the capacity of wild and domestic herbivores to sustain long-distance seed dispersal has been proven, the impact of herbivore corridors in plant population genetics has not been observed previously.

We conducted this study in the Conquense Drove Road in Spain, where sustained use by livestock over centuries has involved transhumant herds passing twice a year en route to winter and summer pastures. We compared genetic diversity and inbreeding coefficients of Plantago lagopus populations along the drove road with populations in the surrounding agricultural matrix, at varying distances from human settlements.

We observed significant differences in coefficients of inbreeding between the drove road and the agricultural matrix, as well as significant trends indicative of higher genetic diversity around human settlements. Trends for higher genetic diversity along drove roads may be present, although they were only marginally significant due to the available sample size.

Our results illustrate a functional landscape with human settlements as dispersal hotspots, while the findings along the drove road confirm its role as a pollinator reservoir observed in other studies. Drove roads seem also to function as linear structures that facilitate long-distance dispersal across the agricultural matrix, while local P. lagopus populations depend rather on short-distance seed dispersal. These results highlight the role of herbivore corridors for conserving the migration capacity of plants and contribute towards understanding the role of seed dispersal and the spread of invasive species related to human activities. The coupling of traditional pastoralist practices with the phenology of plants and pollinators raises concerns on the environmental effects of current global land use change.

This paper is based on García-Fernández et al. (2019).