Seed dispersal networks in tropical forest fragments: Area effects, remnant species, and interaction diversity

Author(s)

Emer, Carine ^[1] ; Jordano, Pedro ^[2] ; Pizo, Marco A. ^[3] ; Ribeiro, Milton C. ^[1] ; da Silva, Fernanda R. ^[4] ; Galetti, Mauro ^{[5, 1]}

Affiliation

^[1] Univ Estadual Paulista UNESP, Inst Biociencias, Dept Ecol, CP 199, BR-13506900 Rio Claro, SP - Brazil

^[2] CSIC, Integrat Ecol Grp, EBD, Seville - Spain

^[3] Univ Estadual Paulista UNESP, Dept Zool, Rio Claro, SP - Brazil

^[4] Univ Campinas UNICAMP, Inst Biol, Campinas, SP - Brazil

^[5] Univ Miami, Dept Biol, Coral Gables, FL 33124 - USA

• Document type: Journal article
• Source: Biotropica; v. 52, n. 1 DEC 2019.
• Web of Science Citations: 0

Abstract

Seed dispersal interactions involve key ecological processes in tropical forests that help to maintain ecosystem functioning. Yet this functionality may be threatened by increasing habitat loss, defaunation, and fragmentation. However, generalist species, and their interactions, can benefit from the habitat change caused by human disturbance while more specialized interactions mostly disappear. Therefore, changes in the structure of the local, within fragment, networks can be expected. Here we investigated how the structure of seed dispersal networks changes along a gradient of increasing habitat fragmentation. We analyzed 16 bird seed dispersal assemblages from forest fragments of a biodiversity-rich ecosystem. We found significant species-, interaction-, and network-area relationships, yet the later was determined by the number of species remaining in each community. The number of frugivorous bird and plant species, their interactions, and the number of links per species decreases as area is lost in the fragmented landscape. In contrast, network nestedness has a negative relationship with fragment area, suggesting an increasing generalization of the network structure in the gradient of fragmentation. Network specialization was not significantly affected by area, indicating that some network properties may be invariant to disturbance. Still, the local extinction of partner species, paralleled by a loss of interactions and specialist-specialist bird-plant seed dispersal associations, suggests the functional homogenization of the system as area is lost. Our study provides empirical evidence for network-area relationships driven by the presence/absence of remnant species and the interactions they perform. in Spanish is available with online material. (AU)

• FAPESP's process: 15/15172-7 - Effects of defaunation and introduction of exotic species on plant-seed dispersal interaction networks
• Grantee: Carine Emer
• Support type: Scholarships in Brazil - Post-Doctorate
• FAPESP's process: 14/01986-0 - Ecological consequences of defaunation in the Atlantic Rainforest
• Grantee: Mauro Galetti Rodrigues
• Support type: Research Projects - Thematic Grants