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1.
Pest Manag Sci ; 79(8): 2912-2919, 2023 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-36977969

RESUMO

BACKGROUND: Understanding the factors that promote the success of invasive species is important for managing biological invasions. Interactions between invasives and other species (e.g. competitors, pathogens, or predators), could favor or limit their success. In recent decades, yellowjacket wasps, including Vespula germanica and Vespula vulgaris, have successfully established in Patagonia. Additionally, the invasive willow Salix fragilis has invaded areas next to watercourses, which in turn are typically colonized by the giant willow aphid (GWA, Tuberolagnus salignus), an additional species characterized as a successful invader in many regions worldwide. Aphid exudate (honeydew) has been reported to be used as a carbohydrate source by social wasps. The aim of our study was to gain a better understanding of the infestation pattern of the GWA in north-western Patagonia, its effect on exudate availability and its relationship with yellowjacket foraging patterns. The study was conducted under the working hypothesis that the increase in the size of GWA colonies and resulting honeydew production, will fuel an increase in local Vespula spp. RESULTS: We found that the aphid honeydew is produced in relatively high amounts in the region (estimated at 1517 ± 139 kg/ha/season), with strong indications that it is used by yellowjackets because of the significantly higher abundance levels of yellowjackets foraging on honeydew compared to nearby areas. CONCLUSION: Given its effect on yellowjacket foraging behavior, the interaction of these three invasive species, willows, GWA and yellowjackets, needs to receive special attention to develop future environmentally-sound mitigation tools of these nuisance pest. © 2023 Society of Chemical Industry.


Assuntos
Afídeos , Heterópteros , Mariposas , Salix , Vespas , Animais , Espécies Introduzidas
2.
Ecol Appl ; 31(2): e02235, 2021 03.
Artigo em Inglês | MEDLINE | ID: mdl-33048392

RESUMO

Although lowland tropical rain forests were once widely believed to be the archetype of stability, seasonal variation exists. In these environments, seasonality is defined by rainfall, leading to a predictable pattern of biotic and abiotic changes. Only the full annual cycle reveals niche breadth, yet most studies of tropical organisms ignore seasonality, thereby underestimating realized conditions. If human-modified habitats display more seasonal stress than intact habitats, then ignoring seasonality will have particularly important repercussions for conservation. We examined the seasonal dynamics of Amazonian mixed-species flocks, an important species interaction network, across three habitats with increasing human disturbance. We quantified seasonal space use, species richness and attendance, and four ecological network metrics for flocks in primary forest, small forest fragments, and regenerating secondary forest in central Amazonia. Our results indicate that, even in intact, lowland rain forest, mixed-species flocks exhibit seasonal differences. During the dry season, flocks included more species, generally ranged over larger areas, and displayed network structures that were less complex and less cohesive. We speculate that-because most flocking species nest during the dry season, a time of reduced arthropod abundance-flocks are simultaneously constrained by these two competing pressures. Moreover, these seasonal differences were most pronounced in forest fragments and secondary forest, habitats that are less buffered from the changing seasons. Our results suggest that seasonality influences the conservation value of human-modified habitats, raising important questions about how rain forest organisms will cope with an increasingly unstable climate.


Assuntos
Florestas , Floresta Úmida , Brasil , Ecossistema , Humanos , Estações do Ano , Árvores , Clima Tropical
3.
PeerJ ; 7: e7566, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31534845

RESUMO

The structure of ecological interactions is commonly understood through analyses of interaction networks. However, these analyses may be sensitive to sampling biases with respect to both the interactors (the nodes of the network) and interactions (the links between nodes), because the detectability of species and their interactions is highly heterogeneous. These ecological and statistical issues directly affect ecologists' abilities to accurately construct ecological networks. However, statistical biases introduced by sampling are difficult to quantify in the absence of full knowledge of the underlying ecological network's structure. To explore properties of large-scale ecological networks, we developed the software EcoNetGen, which constructs and samples networks with predetermined topologies. These networks may represent a wide variety of communities that vary in size and types of ecological interactions. We sampled these networks with different mathematical sampling designs that correspond to methods used in field observations. The observed networks generated by each sampling process were then analyzed with respect to the number of components, size of components and other network metrics. We show that the sampling effort needed to estimate underlying network properties depends strongly both on the sampling design and on the underlying network topology. In particular, networks with random or scale-free modules require more complete sampling to reveal their structure, compared to networks whose modules are nested or bipartite. Overall, modules with nested structure were the easiest to detect, regardless of the sampling design used. Sampling a network starting with any species that had a high degree (e.g., abundant generalist species) was consistently found to be the most accurate strategy to estimate network structure. Because high-degree species tend to be generalists, abundant in natural communities relative to specialists, and connected to each other, sampling by degree may therefore be common but unintentional in empirical sampling of networks. Conversely, sampling according to module (representing different interaction types or taxa) results in a rather complete view of certain modules, but fails to provide a complete picture of the underlying network. To reduce biases introduced by sampling methods, we recommend that these findings be incorporated into field design considerations for projects aiming to characterize large species interaction networks.

4.
Proc Biol Sci ; 285(1885)2018 08 22.
Artigo em Inglês | MEDLINE | ID: mdl-30135157

RESUMO

Understanding the variation in species interactions along environmental stress gradients is crucial for making robust ecological predictions about community responses to changing environmental conditions. The facilitation-competition framework has provided a strong basis for predictions (e.g. the stress-gradient hypothesis, SGH), yet the mechanisms behind patterns in animal interactions on stress gradients are poorly explored in particular for mobile animals. Here, we proposed a conceptual framework modelling changes in facilitation costs and benefits along stress gradients and experimentally tested this framework by measuring fitness outcomes of benefactor-beneficiary interactions across resource quality levels. Three arthropod consumer models from a broad array of environmental conditions were used including aquatic detritivores, potato moths and rainforest carrion beetles. We detected a shift to more positive interactions at increasing levels of stress thereby supporting the application of the SGH to mobile animals. While most benefactors paid no significant cost of facilitation, an increase in potato moth beneficiary's growth at high resource stress triggered costs for benefactors. This study is the first to experimentally show that both costs and benefits function simultaneously on stress gradients for animals. The proposed conceptual framework could guide future studies examining species interaction outcomes for both animals and plants in an increasingly stressed world.


Assuntos
Crustáceos/fisiologia , Insetos/fisiologia , Estresse Fisiológico , Animais , Besouros/fisiologia , Modelos Biológicos , Mariposas/fisiologia , Floresta Úmida , Rios , Solanum tuberosum , América do Sul
5.
Am J Bot ; 103(10): 1753-1762, 2016 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-27562207

RESUMO

PREMISE OF THE STUDY: Fig trees and their pollinators, fig wasps, present a powerful model system for studying mutualism stability: both partners depend on each other for reproduction, cooperation levels can be manipulated, and the resulting field-based fitness quantified. Previous work has shown that fig trees can severely reduce the fitness of wasps that do not pollinate by aborting unpollinated figs or reducing the number and size of wasp offspring. Here we evaluated four hypotheses regarding the mechanism of sanctions in four Panamanian fig species. METHODS: We examined wasp and fig samples from field experiments with manipulated levels of pollination. KEY RESULTS: In unpollinated figs, the fig wall and the wasp offspring had a lower dry mass. Unpollinated figs had as many initiated wasp galls as pollinated figs but fewer galls that successfully produced live wasp offspring. Across three experimentally increasing levels of pollination, we found nonlinear increases in fig wall mass, the proportion of wasp galls that develop, and wasp mass. CONCLUSIONS: Our data did not support the hypotheses that lack of pollination prevents gall formation or that fertilized endosperm is required for wasp development. While our data are potentially consistent with the hypothesis that trees produce a wasp-specific toxin in response to lack of pollination, we found the hypothesis that sanctions are a consequence of trees allocating more resources to better-pollinated figs more parsimonious with the aggregate data. Our findings are completely analogous to the selective resource allocation to more beneficial tissues documented in other mutualistic systems.


Assuntos
Ficus/fisiologia , Polinização , Simbiose , Vespas/fisiologia , Animais , Larva/crescimento & desenvolvimento , Larva/fisiologia , Panamá , Reprodução , Vespas/crescimento & desenvolvimento
6.
Proc Biol Sci ; 282(1815)2015 Sep 22.
Artigo em Inglês | MEDLINE | ID: mdl-26378216

RESUMO

Colour polymorphisms are a striking example of phenotypic diversity, yet the sources of selection that allow different morphs to persist within populations remain poorly understood. In particular, despite the importance of aggression in mediating social dominance, few studies have considered how heterospecific aggression might contribute to the maintenance or divergence of different colour morphs. To redress this gap, we carried out a field-based study in a Nicaraguan crater lake to investigate patterns of heterospecific aggression directed by the cichlid fish, Hypsophrys nicaraguensis, towards colour polymorphic cichlids in the genus Amphilophus. We found that H. nicaraguensis was the most frequent territorial neighbour of the colour polymorphic A. sagittae. Furthermore, when manipulating territorial intrusions using models, H. nicaraguensis were more aggressive towards the gold than dark colour morph of the sympatric Amphilophus species, including A. sagittae. Such a pattern of heterospecific aggression should be costly to the gold colour morph, potentially accounting for its lower than expected frequency and, more generally, highlighting the importance of considering heterospecific aggression in the context of morph frequencies and coexistence in the wild.


Assuntos
Agressão , Ciclídeos/genética , Ciclídeos/fisiologia , Cor , Polimorfismo Genético , Animais , Comportamento Competitivo , Nicarágua , Pigmentação/genética , Territorialidade
7.
Conserv Biol ; 27(4): 763-73, 2013 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-23551525

RESUMO

Mutualistic networks are critical to biological diversity maintenance; however, their structures and functionality may be threatened by a swiftly changing world. In the Amazon, the increasing number of dams poses a large threat to biological diversity because they greatly alter and fragment the surrounding landscape. Tight coevolutionary interactions typical of tropical forests, such as the ant-myrmecophyte mutualism, where the myrmecophyte plants provide domatia nesting space to their symbiotic ants, may be jeopardized by the landscape changes caused by dams. We analyzed 31 ant-myrmecophyte mutualistic networks in undisturbed and disturbed sites surrounding Balbina, the largest Central Amazonian dam. We tested how ant-myrmecophyte networks differ among dam-induced islands, lake edges, and undisturbed forests in terms of species richness, composition, structure, and robustness (number of species remaining in the network after partner extinctions). We also tested how landscape configuration in terms of area, isolation, shape, and neighborhood alters the structure of the ant-myrmecophyte networks on islands. Ant-myrmecophytic networks were highly compartmentalized in undisturbed forests, and the compartments had few strongly connected mutualistic partners. In contrast, networks at lake edges and on islands were not compartmentalized and were negatively affected by island area and isolation in terms of species richness, density, and composition. Habitat loss and fragmentation led to coextinction cascades that contributed to the elimination of entire ant-plant compartments. Furthermore, many myrmecophytic plants in disturbed sites lost their mutualistic ant partners or were colonized by opportunistic, nonspecialized ants. Robustness of ant-myrmecophyte networks on islands was lower than robustness near lake edges and in undisturbed forest and was particularly susceptible to the extinction of plants. Beyond the immediate habitat loss caused by the building of large dams in Amazonia, persistent edge effects and habitat fragmentation associated with dams had large negative effects on animal-plant mutualistic networks.


Assuntos
Formigas/fisiologia , Demografia , Ecossistema , Plantas , Rios , Simbiose/fisiologia , Animais , Brasil , Conservação dos Recursos Naturais/tendências , Modelos Lineares , Especificidade da Espécie , Árvores
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