Mutualistic relationships under landscape change: Carnivorous mammals and plants after 30 years of land abandonment

Little is currently known about the dynamics of mutualistic interactions in relation to land abandonment. Using data from two studies on frugivory and seed dispersal by carnivorous mammals carried out at the same site, and spanning three decades, we show how plant-frugivore interactions change in the long-term after a process of land abandonment in a mountainous area of NW Spain. Over time, the change in the identities of interacting species was small. However, considering the quantitative participation of each species along with the identity and number of strong links, the change was significant. After land abandonment, two successional plant species (rowan and bramble) and a cultivated species (cherry tree) dominated the interactions with carnivores and red foxes replaced pine martens as the main frugivores. The prevalence of cherry tree increased significantly in this sub-web, probably as a consequence of the preference of carnivores for human-selected fruits (higher pulp/seed ratio) and the abandonment of harvesting as a result of the declining human population. Our results suggest that the frequency of interactions between plants and carnivores may be modulated by plant abundance, which in turn is primarily influenced by land abandonment in this scenario, fruit preference by dispersers and the interaction between these two factors. The temporal assessment of plant-animal mutualisms appears to be a valuable tool to predict the course of successional processes. A functional consequence of red foxes as the main frugivore is a higher frequency of long-distance seed dispersal events, which increases connectivity among plant populations, favors colonization and ultimately may shape the course of the successional process. Our study exemplifies the pressing need for more information on the temporal dynamics of ecological interactions in order to understand how they respond to anthropogenic changes such as land abandonment.