Functional importance of avian seed dispersers changes in response to human-induced forest edges in tropical seed-dispersal networks

Saavedra, Francisco; Hensen, Isabell; Beck, Stephan; Böhning‐Gaese, Katrin; Lippok, Denis; Töpfer, Till; Schleuning, Matthias

doi:10.1007/s00442-014-3056-x

Cited by 61 publications

(69 citation statements)

References 60 publications

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“…As a consequence of the usual focal sampling of individual fruiting plants, this kind of seed dispersal event has been generally unrecorded or unconsidered in studies of seed dispersal by avian frugivores (but see Saavedra et al. ). Finally, the widespread behavior of parrots wasting large amounts of ripe fruits and their seeds while feeding on fruiting plants has lacked a functional explanation (e.g., Symes and Perrin ), but undoubtedly may facilitate both primary and secondary dispersal.…”

Section: Discussionmentioning

confidence: 99%

Parrots as key multilinkers in ecosystem structure and functioning

Blanco

Hiraldo

Rojas

et al. 2015

Ecology and Evolution

128

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Mutually enhancing organisms can become reciprocal determinants of their distribution, abundance, and demography and thus influence ecosystem structure and dynamics. In addition to the prevailing view of parrots (Psittaciformes) as plant antagonists, we assessed whether they can act as plant mutualists in the dry tropical forest of the Bolivian inter‐Andean valleys, an ecosystem particularly poor in vertebrate frugivores other than parrots (nine species). We hypothesised that if interactions between parrots and their food plants evolved as primarily or facultatively mutualistic, selection should have acted to maximize the strength of their interactions by increasing the amount and variety of resources and services involved in particular pairwise and community–wide interaction contexts. Food plants showed different growth habits across a wide phylogenetic spectrum, implying that parrots behave as super‐generalists exploiting resources differing in phenology, type, biomass, and rewards from a high diversity of plants (113 species from 38 families). Through their feeding activities, parrots provided multiple services acting as genetic linkers, seed facilitators for secondary dispersers, and plant protectors, and therefore can be considered key mutualists with a pervasive impact on plant assemblages. The number of complementary and redundant mutualistic functions provided by parrots to each plant species was positively related to the number of different kinds of food extracted from them. These mutually enhancing interactions were reflected in species‐level properties (e.g., biomass or dominance) of both partners, as a likely consequence of the temporal convergence of eco‐(co)evolutionary dynamics shaping the ongoing structure and organization of the ecosystem. A full assessment of the, thus far largely overlooked, parrot–plant mutualisms and other ecological linkages could change the current perception of the role of parrots in the structure, organization, and functioning of ecosystems.

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Section: Discussionmentioning

confidence: 99%

Parrots as key multilinkers in ecosystem structure and functioning

Blanco

Hiraldo

Rojas

et al. 2015

Ecology and Evolution

128

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“…This could be due to differences in sampling effort and completeness among the studied networks. For instance, we would expect that the degree of trait matching is weakened in modified ecological communities that are dominated by small-bodied species (Saavedra et al 2014). Moreover, we compared communities that differed widely in their species pools.…”

Section: Trait Matching Across the Andesmentioning

confidence: 99%

Morphological trait matching shapes plant–frugivore networks across the Andes

et al. 2018

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Interactions between resource and consumer species are organized in ecological networks. Species interactions in these networks are influenced by the functional traits of the interacting partners, but the generality of trait-based interaction rules and the relationship between functional traits and a species' specialization on specific interaction partners are not yet understood. Here we combine data on eight interaction networks between fleshy-fruited plants and frugivorous birds sampled across the tropical and subtropical Andean range. We test which combinations of morphological plant and animal traits determine trait matching between resource and consumer species in these networks. In addition, we test which of the morphological traits influence functional specialization of plant and bird species. In a meta-analysis across network-specific fourth-corner analyses, we found that plant-animal trait pairs related to size matching (fruit size-beak size) and avian foraging behavior (plant height-wing shape and crop mass-body mass) were positively related in these networks. The degree of functional specialization on specific interaction partners was positively related to crop mass in plants and to the pointedness of the wing in birds. Our findings show that morphological trait matching between fleshy-fruited plants and frugivorous birds is a general phenomenon in plant-frugivore networks across the Andes and that specific plant and bird traits can be used to approximate the degree of functional specialization. These insights into the generality of interaction rules are the base for predictions of species interactions in ecological networks, for instance in novel communities in the future, and can be applied to identify plant and animal species that fulfill specialized functional roles in ecological communities.

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“…However, previous studies in the tropical Andes have shown that biological processes, such as seed dispersal, can be enhanced at forest edges (Saavedra et al. ), which could potentially contribute to the regeneration of deforested habitats by pioneer tree species (Tabarelli et al. ; Heelemann et al.…”

Section: Introductionmentioning

confidence: 99%

Deforested habitats lack seeds of late‐successional and large‐seeded plant species in tropical montane forests

Saavedra

Hensen

Schleuning

2015

Applied Vegetation Science

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Questions (1) How do seed density and species richness of late‐successional, pioneer and non‐forest species change from forest interior to deforested habitats? (2) Are seed density and species richness of seed species dispersed into deforested areas enhanced by perch structures? (3) Do morphological seed traits of forest and non‐forest plant species change from the forest interior to deforested areas? Location Deforested tropical mountains of Chulumani, La Paz, Bolivia. Methods At eight study sites, we installed a system of 38 seed traps along a transect of 240 m from the forest interior (160 m from the forest margin) toward deforested areas (80 m from the forest margin). Half of the seed traps installed in the deforested areas were positioned under perch structures. We identified captured seeds to morpho‐species or species level and recorded morphological seed traits (i.e. seed mass, seed length, seed width) and species origin (i.e. late‐successional, pioneer, non‐forest species). Results Seed density and species richness of late‐successional and pioneer species declined from the forest interior toward deforested areas. Seed limitation was particularly strong for large‐seeded species. Perches in deforested areas strongly increased the density and to some extent as well as the species richness of seeds dispersed into these areas, but did not alter the composition of seed traits and species origin in comparison to seed traps without perches. Conclusions We found a strong seed dispersal limitation in deforested areas, which was mitigated by the presence of perch structures, at least in terms of seed density and species richness. However, the dispersal limitation of late‐successional plant species with large seeds was not compensated by the presence of perching structures. Nevertheless, the establishment of artificial perch structures is likely to be a promising strategy for capturing seeds in deforested areas that may establish under bracken fronds in the long term.

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Functional importance of avian seed dispersers changes in response to human-induced forest edges in tropical seed-dispersal networks

Cited by 61 publications

References 60 publications

Parrots as key multilinkers in ecosystem structure and functioning

Parrots as key multilinkers in ecosystem structure and functioning

Morphological trait matching shapes plant–frugivore networks across the Andes

Deforested habitats lack seeds of late‐successional and large‐seeded plant species in tropical montane forests

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