Landscape Constraints on Functional Diversity of Birds and Insects in Tropical Agroecosystems

Abstract

In this paper, we analyze databases [corrected] on birds and insects to assess patterns of functional diversity in human-dominated landscapes in the tropics. A perspective from developed landscapes is essential for understanding remnant natural ecosystems, because most species experience their surroundings at spatial scales beyond the plot level, and spillover between natural and managed ecosystems is common. Agricultural bird species have greater habitat and diet breadth than forest species. Based on a global data base, bird assemblages in tropical agroforest ecosystems were composed of disproportionately more frugivorous and nectarivorous, but fewer insectivorous bird species compared with forest. Similarly, insect predators of plant-feeding arthropods were more diverse in Ecuadorian agroforest and forest compared with rice and pasture, while, in Indonesia, bee diversity was also higher in forested habitats. Hence, diversity of insectivorous birds and insect predators as well as bee pollinators declined with agricultural transformation. In contrast, with increasing agricultural intensification, avian pollinators and seed dispersers initially increase then decrease in proportion. It is well established that the proximity of agricultural habitats to forests has a strong influence on the functional diversity of agroecosystems. Community similarity is higher among agricultural systems than in natural habitats and higher in simple than in complex landscapes for both birds and insects, so natural communities, low-intensity agriculture, and heterogeneous landscapes appear to be critical in the preservation of beta diversity. We require a better understanding of the relative role of landscape composition and the spatial configuration of landscape elements in affecting spillover of functionally important species across managed and natural habitats. This is important for data-based management of tropical human-dominated landscapes sustaining the capacity of communities to reorganize after disturbance and to ensure ecological functioning.

Establishing the evidence base for maintaining biodiversity and ecosystem function in the oil palm landscapes of South East Asia

“…Higher heterogeneity within an area is frequently associated with a higher diversity of species, and this complexity may be associated with factors operating at everything from the local to the landscape scale. For example, both local-and landscape-scale variables have been found to be important in structuring bird communities in forest areas in Borneo [91], and the interaction at the landscape scale between managed and natural habitats may be crucial for maintaining functional diversity within managed landscapes [92]. We will consider independently approaches that might be effective at the landscape and at the more local scale.…”

Species richness matters for the quality of ecosystem services: a test using seed dispersal by frugivorous birds

“…Frugivore assemblages and seed dispersal comprise an optimal system for testing the prevalence of the biodiversityecosystem services link in the real world for several reasons. First, frugivore assemblages are composed of species that usually differ strongly in their relative abundance and functionality [20,21]. Second, different drivers of global change, e.g.…”

Habitat fragmentation reduces nest survival in an Afrotropical bird community in a biodiversity hotspot

“…Habitat fragmentation results in a reduction in area, an increase in remnant isolation, the creation of edge, and an alteration in the habitat structure of the remnants, all of which may contribute either directly or indirectly to changes in avian nest survival (3-6). Given that nearly two thirds of all bird species are endemic to the tropics (7,8) and that moist tropical forests are being lost worldwide at a rate of 0.52% annually (9), understanding the impact of habitat fragmentation on the demography of tropical birds is clearly important for avian conservation.However, because of the difficulty of finding large numbers of well-hidden nests in tropical forests (10, 11), rigorously assessing the impact of habitat fragmentation on avian nest survivorship has been challenging. Previous studies comparing avian nest survivorship between fragmented and intact forest in the tropics have either used artificial nests and eggs (12, 13), which unfortunately often poorly mimic the fate of real nests and eggs (14-16); or if real nests have been found, have lumped species together in the analysis because of small sample sizes (17), which can be misleading because nest survivorship can vary locally among tropical bird species (18-21).…”

“…Habitat fragmentation results in a reduction in area, an increase in remnant isolation, the creation of edge, and an alteration in the habitat structure of the remnants, all of which may contribute either directly or indirectly to changes in avian nest survival (3-6). Given that nearly two thirds of all bird species are endemic to the tropics (7,8) and that moist tropical forests are being lost worldwide at a rate of 0.52% annually (9), understanding the impact of habitat fragmentation on the demography of tropical birds is clearly important for avian conservation.…”