BUSCADOR RECOLECTA

Apex predators play key roles in food webs and their recovery can trigger trophic cascades in some ecosystems. Intra-guild competition can reduce the abundances of smaller predators and perceived predation risk can alter their foraging behaviour thereby limiting seed dispersal by frugivorous carnivores. However, little is known about how plant–frugivore mutualisms could be disturbed in the presence of larger predators. We evaluated the top-down effect of the regional superpredator, the Iberian lynx Lynx pardinus, on the number of visits and fruits consumed by medium-sized frugivorous carnivores, as well as the foraging behaviour of identified individuals, by examining the consumption likelihood and the foraging time. We carried out a field experiment in which we placed Iberian pear Pyrus bourgaeana fruits beneath fruiting trees and monitored pear removal by frugivorous carnivores, both inside and outside lynx ranges. Using camera traps, we recorded the presence of the red fox Vulpes vulpes, the Eurasian badger Meles meles and the stone marten Martes foina, as well as the number of fruits they consumed and their time spent foraging. Red fox was the most frequent fruit consumer carnivore. We found there were fewer visits and less fruit consumed by foxes inside lynx ranges, but lynx presence did not seem to affect badgers. We did not observe any stone marten visits inside lynx territories. The foraging behaviour of red foxes was also altered inside lynx ranges whereby foxes were less efficient, consuming less fruit per unit of time and having shorter visits. Local availability of fruit resources, forest coverage and individual personality also were important variables to understand visitation and foraging in a landscape of fear. Our results show a potential trophic cascade from apex predators to primary producers. The presence of lynx can reduce frugivorous carnivore numbers and induce shifts in their feeding behaviour that may modify the seed dispersal patterns with likely consequences for the demography of many fleshy-fruited plant species. We conclude that knowledge of the ecological interactions making up trophic webs is an asset to design effective conservation strategies, particularly in rewilding programs., Ministerio de Ciencia, Innovación y Universidades, Grant/Award Number: CGL2017-84633-P and FPU17/04375

This study was partially supported by Spanish Minister of Science and Innovation and Universities (ref. PID2022-142067NB-I00, CGL2017- 84633- P, FPU17/04375)., Peer reviewed

Number and frequency of visits to Pyrus bourgaeana trees in southern Spain. The number of visits has been added to this file for first time., PID2022-142067NB-I00
CGL2017- 84633- P
FPU17/04375, Peer reviewed

Current global change scenarios demand knowledge on how anthropogenic impacts affect ecosystem functioning through changes in food web structure. Frugivorous mesocarnivores are a key link in trophic cascades because, while their abundance and behaviour are usually controlled by apex predators, they can provide high-quality seed-dispersal services to plant communities. Thus, the recent rewilding of large carnivores worldwide can trigger cascading effects for plants. We investigated the top-down effects of an apex predator (Iberian lynx Lynx pardinus) on seed-dispersal services mediated by two mesocarnivore species (red fox Vulpes vulpes and stone marten Martes foina) at the plant community level by comparing areas with and without lynx in a Mediterranean mountain range in Southern Spain. We collected scats of mesocarnivores (n = 1575) to assess frugivory and seed dispersal of 15 plant species over two consecutive fruiting seasons and two habitat types (open and forest). Specifically, we assessed the effect of lynx presence on (i) seed occurrence and fleshy-fruit biomass per scat, (ii) the number of scats containing seeds, and (iii) the diversity of dispersed seeds. The quantity and diversity of dispersed seeds drastically decreased under predation risk for both mesocarnivore species. Seed dispersal by stone martens was negatively affected by the presence of lynx, with a marked reduction in the number of scats with seeds (93%) and the diversity of dispersed seeds (46%). Foxes dispersed 68% fewer seeds in open habitats when coexisting with lynx, probably leading to differential contributions to seed-dispersal effectiveness among habitats. Our study reveals a novel trophic cascade from apex predators to plant communities. The behavioural responses of frugivorous mesocarnivores to predation risk and the reduction in the intensity of their faecal deposition pattern are probably related to their lower abundance when co-occurring with apex predators. While rewilding apex predators is a successful conservation tool, attention should be paid to cascading effects across food webs, particularly where frugivore megafauna are missing and mesocarnivores provide unique services to plant communities., Ministerio de Ciencia e Innovación: CGL2017-84633-P, Generación de conocimiento
Ministerio de Ciencia e Innovación: FPU17/04375, Formación del profesorado universitario, Peer reviewed

Mesopredators abundance is often limited by top-order predators and also by key food resources. However, the contribution of these bidirectional forces to structure carnivore community is still unclear. Here, we studied how the presence and absence of an apex predator which is currently recovering its former distribution range, the Iberian lynx (Lynx pardinus), determined the absolute abundance and fine-scale spatiotemporal avoidance mechanisms of two sympatric mesocarnivores (stone marten Martes foina and common genet Genetta genetta) with different dietary plasticity. We hypothesized that the lynx causes a mesopredator suppression and subordinate predators develop segregation strategies in respect to their trophic niche breadth. We placed 120 camera-traps in Southern Spain for 8 months in two consecutive years to estimate mesocarnivore abundances by using SCR Bayesian models, prey availability and assess spatio-temporal patterns. We found that the lynx reduced mesocarnivore abundance up to 10 times. Stone marten, a mesopredator with a broad food resources spectrum, showed a total spatial exclusion with the apex predator. Meanwhile, fine-scale avoidance mechanisms allowed the genet to persist in low density inside lynx territories, probably taking advantage of high availability of its preferred prey. Thus, the strength of these top-down and bottom-up effects was rather species-specific. Given the recent recovery of large carnivore populations worldwide, variation in suppression levels on different mesopredator species could modify ecosystem functions provided by the carnivore community in contrasting ways.

Current global change scenarios demand knowledge on how anthropogenic impacts affect ecosystem functioning through changes in food web structure. Frugivorous mesocarnivores are a key link in trophic cascades because, while their abundance and behaviour are usually controlled by apex predators, they can provide high-quality seed-dispersal services to plant communities. Thus, the recent rewilding of large carnivores worldwide can trigger cascading effects for plants. We investigated the top-down effects of an apex predator (Iberian lynx Lynx pardinus) on seed-dispersal services mediated by two mesocarnivore species (red fox Vulpes vulpes and stone marten Martes foina) at the plant community level by comparing areas with and without lynx in a Mediterranean mountain range in Southern Spain. We collected scats of mesocarnivores (n = 1575) to assess frugivory and seed dispersal of 15 plant species over two consecutive fruiting seasons and two habitat types (open and forest). Specifically, we assessed the effect of lynx presence on (i) seed occurrence and fleshy-fruit biomass per scat, (ii) number of scats containing seeds and (iii) diversity of dispersed seeds. The quantity and diversity of dispersed seeds drastically decreased under predation risk for both mesocarnivore's species. Seed dispersal by stone martens was negatively affected by the presence of lynx, with a marked reduction in the number of scats with seeds (93%) and the diversity of dispersed seeds (46%). Foxes dispersed 68% fewer seeds in open habitats when coexisting with lynx, probably leading to differential contributions to seed-dispersal effectiveness among habitats. Our study reveals a novel trophic cascade from apex predators to plant communities. The behavioural responses of frugivorous mesocarnivores to predation risk and the reduction in the intensity of their faecal deposition pattern are probably related to their lower abundance when co-occurring with apex predators. While rewilding apex predators is a successful conservation tool, attention should be paid to cascading effects across food webs, particularly where frugivore megafauna is missing and mesocarnivores provide unique services to plants.

The Seed Dispersal Syndrome Hypothesis (SDSH) posits that fruit traits predict the main dispersers interacting with plant species. Mammalian dispersers, relying heavily on olfactory cues, are expected to select dull-colored, scented, and larger fruits compared to birds. However, challenges like overabundant seed predators and context-dependency of frugivore-plant interactions complicate SDSH expectations. We studied the Iberian pear, Pyrus bourgaeana, an expected mammal-dispersed tree based on its fruit traits. Extensive camera-trapping data (over 35,000 records) from several tree populations and years revealed visits from seven frugivore groups, with ungulate fruit predators (59–97%) and carnivore seed dispersers (1–20%) most frequent, while birds, lagomorphs, and rodents were infrequent (0–10%). Red deer and wild boar were also the main fruit removers in all sites and years but acted as fruit and seed predators, and thus likely exert conflicting selection pressures to those exerted by seed dispersers. Although, as predicted by the SDSH, most Iberian pear fruits were consumed by large and medium-sized mammals, the traits of Iberian pear fruits likely reflect selection pressures from dispersal vectors in past times. Our results do not challenge the SDHS but do reveal the importance of considering frugivore functional roles for its adequate evaluation.