Directed dispersal by rotational shepherding supports landscape genetic connectivity in a calcareous grassland plant.
Directed dispersal by animal vectors has been found to have large effects on the structure and dynamics of plant populations adapted to frugivory. Yet, empirical data are lacking on the potential of directed dispersal by rotational grazing of domestic animals to mediate gene flow across the landscape. Here, we investigated the potential effect of large-flock shepherding on landscape-scale genetic structure in the calcareous grassland plant Dianthus carthusianorum, whose seeds lack morphological adaptations to dispersal to animals or wind. We found a significant pattern of genetic structure differentiating population within grazed patches of three nonoverlapping shepherding systems and populations of ungrazed patches. Among ungrazed patches, we found a strong and significant effect of isolation by distance (r = 0.56). In contrast, genetic distance between grazed patches within the same herding system was unrelated to geographical distance but significantly related to distance along shepherding routes (r = 0.44). This latter effect of connectivity along shepherding routes suggests that gene flow is spatially restricted occurring mostly between adjacent populations. While this study used nuclear markers that integrate gene flow by pollen and seed, the significant difference in the genetic structure between ungrazed patches and patches connected by large-flock shepherding indicates the potential of directed seed dispersal by sheep across the landscape.
Department of Ecology and Evolutionary Biology, University of Toronto, 3359 Mississauga Road, Mississauga, Ontario, Canada, L5L 1C6; Resources DNA Profiling and Forensics Centre, Trent University, Peterborough, Ontario, Canada, K9J 7B8.
Yessica
Y
Rico
Rolf
R
Holderegger
Hans Juergen
HJ
Boehmer
Helene H
HH
Wagner
D000383:Agriculture / Q000379:methods*; D000818:Animals; D018744:DNA, Plant / Q000235:genetics; D029749:Dianthus / Q000235:genetics*; D017753:Ecosystem; D051456:Gene Flow; D005828:Genetics, Population; D005858:Germany; D018895:Microsatellite Repeats; D058614:Seed Dispersal; D012756:Sheep
D018744:DNA, Plant
Dianthus carthusianorum; Germany; calcareous grasslands; gene flow; landscape genetics; nuclear microsatellites; zoochory