Frugivore biodiversity and complementarity in interaction networks enhance landscape‐scale seed dispersal function

Abstract

Animal biodiversity matters for the provision of ecosystem functions derived from trophic activity. However, the mechanisms underlying this pattern remain elusive since animal abundance and diversity, which are the components commonly used for representing biodiversity, provide poor information about ecological complementarity in species assemblages. An approach based on species interaction networks may overcome this constraint. Here, we relate frugivore biodiversity and frugivore–plant network structure with landscape‐scale seed dispersal function. We sampled, for two years, and at fourteen plots with variable assemblages of frugivores and plants in the Cantabrian Range (N Spain), data on the abundance and diversity of frugivorous birds, the consumption of fleshy fruits of woody plants and the landscape‐scale patterns of avian seed deposition. As a measure of interaction complementarity in seed dispersal networks, we estimated the degree to which frugivore and plant species specialize in their interacting partners. Specialization varied strongly across the seed dispersal networks of the different plots, being higher in networks harbouring smaller bird species that dispersed mostly small‐fruited plants, and also in networks with late‐ripening, dominant fruiting species dispersed mostly by wintering birds. Bird abundance markedly affected seed deposition. Plots harbouring more birds received a higher density of dispersed seeds and showed higher probabilities of seed arrival and seed deposition in open microhabitats. Bird diversity also had a positive effect on the density of dispersed seed and, to a lesser extent, seed arrival probability. Independently of frugivore abundance and diversity, the density of dispersed seeds increased in plots where seed dispersal networks showed a higher degree of specialization. This study considers the structure of interaction networks to re‐address the relationship between biodiversity and ecosystem functionality, evidencing that specialization in frugivore–plant networks drives the large‐scale process of seed dispersal. These results encourage the consideration of interaction complementarity as an underlying mechanism linking animal biodiversity and trophic‐related functions.

Biodiversity components mediate the response to forest loss and the effect on ecological processes of plant–frugivore assemblages

“…Indeed, a cascade effect is to be expected, by which the response of one trophic level to disturbance will impact on the fitness of the other trophic level involved. In our specific case, from the point of view of plants, we might also assume that some indirect, negative consequences will emerge from bird functional decay, as the loss of specialized seed dispersers has been found to decrease the magnitude of seed deposition in this study system (García et al, 2018). We therefore argue that our findings can be extended to different trophic processes (e.g.…”

“…For both trophic levels, these differences were related to the changes in trait‐based functional diversity, with greater trait dispersion encompassing higher functional complementarity in frugivory (see also Dehling et al, 2016). This pattern seems related primarily to the inclusion of small‐sized fruits and their specialized frugivores in interaction networks (García, Donoso, & Rodríguez‐Pérez, 2018). Namely, small‐sized drupes, like elder Sambucus nigra and blackberry, are mostly eaten by small birds such as blackcap, but also by other, larger species, such as bullfinch and Eurasian jay, which increase the degree of trait‐based functional diversity in local bird assemblages.…”

From structure to function in mutualistic interaction networks: Topologically important frugivores have greater potential as seed dispersers

“…Although the structural generalities of animal-plant mutualistic interactions are well known, we are still far from understanding the functional consequences of variability in network structure (Fricke, Bender, Rehm, & Rogers, 2018;García, Donoso, & Rodríguez-Pérez, 2018).…”

“…plant community-wide seed dispersal) in temperate and tropical ecosystems (e.g. García et al, 2018;Jordano, 2014;Jordano et al, 2011). Contribution to the process of seed dispersal, and to the concomitant plant recruitment, varies widely among frugivore species, depending on the species and the quantity of fruit consumed, and the type of handling of fruits and seeds during consumption (with some frugivores destroying seeds while feeding on fruits, whereas others drop them intact after regurgitation or defecation; Jordano, 2014;Simmons et al, 2018).…”

Exploratory Studies on Occurrence and Potential Benefits of High Fruit Yielding Reproductive Phenophasic Variants of Pithecellobium dulce in Augmenting Fruit Based Semi-arid Agro Forestry Systems

“…Consequently, overall fruit yield is drastically reduced and fruit to flower ratio is very poor. [69], and Garcia, 2018 [70] have also emphasised on importance of frugivore diversity in reproductive success of tree species. The phenological shift in flowering is outcomes of interactions between pollinators and other biotic and abiotic factors that led to evolution of long duration flowering in P. dulce, which is exclusively pollinated by insects, therefore, in agreement with Elzinga, 2007 [71], and Munguia-Rosas, 2011 [72], it would be appropriate to state that insect pollinated plants flower for longer durations as compared to abiotically pollinated plants (Fig.…”