Tropical Forest Fragmentation Affects Floral Visitors but Not the Structure of Individual-Based Palm-Pollinator Networks

Dáttilo, Wesley; Aguirre, Armando; Quesada, Maurício; Dirzo, Rodolfo

doi:10.1371/journal.pone.0121275

Cited by 25 publications

(20 citation statements)

References 72 publications

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“…Applying meta-analytical techniques, Magrach et al (2014) demonstrated that the effects of fragmentation on mutualisms were primarily driven by habitat degradation, edge effects, and fragment isolation, with little effect of fragment size. Dattilo et al (2015) found that fragment size did not affect the topological structure of the individual-based palm-pollinator network. However, Aguirre and Dirzo (2008) reported pollinator abundance was negatively affected by fragment size.…”

Section: Discussionmentioning

confidence: 85%

Ecological succession drives the structural change of seed-rodent interaction networks in fragmented forests

Yang

Yan

Zhao

et al. 2018

Forest Ecology and Management

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While deforestation and fragmentation can cause massive species loss in forest ecosystems, forest regeneration can also drive successional changes in species composition. Although studies have sometimes documented the effects of these compositional changes on interspecific interactions, few studies have investigated changes in the structure of plant-animal networks. We investigated how interaction networks of assemblages of rodents and tree seeds changed with forest fragmentation and succession in a subtropical region. We compared seed-rodent interactions between 14 secondary forest patches that ranged in area from 2 to 58 ha, and from 10 to at least 100 years old, representing a successional gradient. We expected that deforestation and fragmentation would reduce seed production and diversify rodent communities, resulting in higher interaction strengths and connectivity, but weak nestedness (i.e., specialists interact with subsets of the species interaction of generalists). We measured the frequency of rodents eating and removing seeds (interaction strength) in each patch during 3 successive years, using seed tagging and infrared camera trapping, and calculated the properties of the seed-rodent networks. We found that the relative abundances of seeds and rodents changed with stand age not patch size, as did seed-rodent interactions: older patches produced more seeds, contained fewer individuals and species of rodents, and had seed-rodent networks with lower connectance and interaction strength, but higher nestedness. Connectance and interaction strength decreased with metabolic per capita seed availability (as measured by seed energy value); nestedness increased with seed richness, but decreased with rodent abundance. At species level, we found stand age and patch size showed significant effects on seed or rodent abundance of a few species. We also found seed coat thickness and starch contents had significant effects on network metrics. Our results suggest that during succession after deforestation, seed-rodent interactions in these subtropical forests change from a state dominated by high seed removal and highly connected seed-rodent networks to a state with more seeds and highly nested networks. From a management perspective of our study region, succession age, not fragment size, and network structure should be paid more attention so as to facilitate the restoration processes of degraded forests. Rodent management should be applied to protect native forest species and exclude incursive ones from farmlands and human residences at early succession stage.

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Section: Discussionmentioning

confidence: 85%

Ecological succession drives the structural change of seed-rodent interaction networks in fragmented forests

Yang

Yan

Zhao

et al. 2018

Forest Ecology and Management

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“…redundancy) in pollinator efficiency, sample under different abiotic conditions and use a range of sampling methods (e.g. collect entire inflorescences to sample beetles; Dáttilo, Aguirre, Quesada, & Dirzo, 2015).…”

Section: Objective 2: To Understand How Flower-visitor Communities mentioning

confidence: 99%

Anthropogenic disturbance of tropical forests threatens pollination services to açaí palm in the Amazon river delta

Campbell

Carvalheiro

Maués

et al. 2018

Journal of Applied Ecology

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The açaí palm Euterpe oleracea Mart. in the Amazon river delta has seen rapid expansion to meet increased demand for its fruit. This has been achieved by transforming lowland forest habitats (floodplains) into simplified agroforests and intensive plantation in upland areas. As açaí palm makes an important contribution to the economy and food security of local communities, identifying management approaches that support biodiversity and ecosystem processes that underpin fruit production on açaí farms is essential. We compared flower‐visitor communities and açaí fruit production in floodplain forests and upland plantations, across gradients of local management intensity (i.e. açaí density per ha) and surrounding forest cover. The relative contribution of biotic pollination and degree of pollen limitation were assessed using insect exclusion and hand‐pollination experiments. We found that açaí flower visitors are highly diverse (c. 200 distinct taxa) and had variable responses to disturbance. Bee visitation was higher in floodplains and positively related to surrounding forest cover, but other flower visitors, including specialised curculionid beetles, were unresponsive to changes in surrounding forest cover. However, intensive management practices (i.e. high açaí palm densities) in floodplains and uplands had contrasting effects on flower‐visitor communities, with flower‐visitor richness being lower on intensively managed floodplain farms and ant densities being higher on intensive upland farms. Pollination experiments revealed açaí palm to be highly dependent on biotic pollination. Fruit set in open‐pollinated inflorescences was positively related to flower‐visitor richness and specialised curculionid beetle visitation, whereas the presence of ants on inflorescences had a negative effect. Synthesis and applications. Our study shows that pollinators are essential for açaí fruit production, but that intensive farming practices have eroded the relationship between surrounding forest cover and ecosystem function in floodplains (i.e. conversion of native forest into simplified agroforests) and increased the frequency of antagonistic interactions in uplands (e.g. high ant densities). These findings underline the value of extensive management practices, such as the maintenance of other tree species within farms and adjacent unmanaged forest patches, to ensure the long‐term sustainability of açaí fruit production in the Amazon river delta.

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“…Furthermore, pollinators in deforested landscapes may occur in smaller number and be less effective than in forested landscapes (Dáttilo et al. ), representing a possible negative influence on the species gene flow distances and possibly driving related processes on the local scale (Breed et al. ).…”

Section: Discussionmentioning

confidence: 99%

Landscape‐scale deforestation decreases gene flow distance of a keystone tropical palm, Euterpe edulis Mart (Arecaceae)

Santos

Cazetta

Dodonov

et al. 2016

Ecology and Evolution

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Habitat loss represents one of the main threats to tropical forests, which have reached extremely high rates of species extinction. Forest loss negatively impacts biodiversity, affecting ecological (e.g., seed dispersal) and genetic (e.g., genetic diversity and structure) processes. Therefore, understanding how deforestation influences genetic resources is strategic for conservation. Our aim was to empirically evaluate the effects of landscape‐scale forest reduction on the spatial genetic structure and gene flow of Euterpe edulis Mart (Arecaceae), a palm tree considered a keystone resource for many vertebrate species. This study was carried out in nine forest remnants in the Atlantic Forest, northeastern Brazil, located in landscapes within a gradient of forest cover (19–83%). We collected leaves of 246 adults and 271 seedlings and performed genotyping using microsatellite markers. Our results showed that the palm populations had low spatial genetic structure, indicating that forest reduction did not influence this genetic parameter for neither seedlings nor adults. However, forest loss decreased the gene flow distance, which may negatively affect the genetic diversity of future generations by increasing the risk of local extinction of this keystone palm. For efficient strategies of genetic variability conservation and maintenance of gene flow in E. edulis, we recommend the maintenance of landscapes with intermediary to high levels of forest cover, that is, forest cover above 40%.

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Tropical Forest Fragmentation Affects Floral Visitors but Not the Structure of Individual-Based Palm-Pollinator Networks

Cited by 25 publications

References 72 publications

Ecological succession drives the structural change of seed-rodent interaction networks in fragmented forests

Ecological succession drives the structural change of seed-rodent interaction networks in fragmented forests

Anthropogenic disturbance of tropical forests threatens pollination services to açaí palm in the Amazon river delta

Landscape‐scale deforestation decreases gene flow distance of a keystone tropical palm, Euterpe edulis Mart (Arecaceae)

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