Herbivore corridors sustain genetic footprint in plant populations: a case for Spanish drove roads.

Alfredo García-Fernández,Begoña Peco,Javier Seoane,Pablo Manzano,Jose M Iriondo,Francisco M Azcárate

doi:10.7717/peerj.7311

Alfredo García-Fernández, Begoña Peco + Show 4 more

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https://doi.org/10.7717/peerj.7311

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Abstract

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 remains to be observed. 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 and population nestedness 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 may possibly also 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.

Highlights

Increased habitat fragmentation has been perceived as a major worldwide threat for ecosystems and biodiversity for the last decades (Fahrig 2003)
We aimed to check whether dispersal processes in drove roads subjected to active use were strong enough to influence the population genetic structure of Plantago lagopus, an annual selfing plant species dispersed by livestock endo- and epizoochory along Spanish drove roads (Manzano et al unpublished)
The genetic structure analyzed with a Bayesian clustering approach (i.e. STRUCTURE) showed two complementary clustering patterns, suggesting that K=2 or K=5 are plausible distributions of the genetic structure

Summary

Introduction

Increased habitat fragmentation has been perceived as a major worldwide threat for ecosystems and biodiversity for the last decades (Fahrig 2003). Extensive fragmentation occurs due to the expansion of road infrastructure (Ibisch et al 2016), agricultural development (Herrera et al 2009), the building of fences (Bartlam-Brooks et al 2011; Said et al 2016) and increasing urban sprawl (Said et al 2016). Affordable mitigation measures reducing fragmentation are problematic because they can have a negative impact on the provision of important ecosystem services to the population (Mitchell et al 2015).

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