Vertically stratified frugivore community composition and interaction frequency in a liana fruiting across forest strata

Thiel, Sarina; Willems, Franziska M.; Farwig, Nina; Rehling, Finn; Schabo, Dana G.; Schleuning, Matthias; Tello, Ney Shahuano; Töpfer, Till; Tschapka, Marco; Heymann, Eckhard W.; Heer, Katrin

doi:10.1111/btp.13216

Cited by 3 publications

(1 citation statement)

References 77 publications

(125 reference statements)

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“…Differential contribution by frugivores to plant consumption was widespread in all populations, supporting previous studies and providing more evidence on how just a few species, even within diversified assemblages, perform most of the mutualistic interactions (Fig. S5, Rother et al 2016, Guerra et al 2017, Isla et al 2023, Rehling et al 2023, Thiel et al 2023). These interaction patterns will result in asymmetric dependencies between plant individuals and frugivore species, where the main frugivore species show low specificity for specific plants, while most plant individuals rely just on the main frugivore’s service (Quintero et al 2023).…”

Section: Discussionsupporting

confidence: 88%

Downscaling mutualistic networks from species to individuals reveals consistent interaction niches and roles within plant populations

Quintero,

Arroyo-Correa,

Isla

et al. 2024

Preprint

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The study of mutualistic interactions among species has received considerable attention over the past 30 years. However, less is known about the structure of individual interaction configurations within species. Recently, individual-based networks have begun to garner more attention, as they represent the fundamental scale at which ecological interactions are assembled.We compiled 44 empirical individual-based networks on plant-animal seed dispersal mutualism, encompassing 995 plant individuals across 28 species from various regions. We compare the structure of individual-based networks to that of species-based networks and by extending the niche concept to interaction assemblages, we explore levels of individual plant specialization. We examine how individual variation influences network structure and how plant individuals “explore” the interaction niche of the population.Both individual-based and species-based networks exhibited high variability in network properties, leading to a lack of marked structural and topological differences between them. Our results reveal low to medium specialization, with European populations exhibiting higher generality compared to American and Asian populations. Within populations, frugivores’ interaction allocation among plant individuals was highly heterogeneous, with one to three frugivore species dominating interactions in most populations.Regardless of plant species or geographical region, plant individuals displayed similar interaction profiles across populations, with only a few individuals playing a central role and exhibiting high diversity in the interaction assemblage.Our results emphasize the importance of downscaling from species-based to individual-based networks to understand the structuring of any given ecological community and provide an empirical basis for the extension of niche theory to complex interaction networks.Significance StatementEcological interactions in nature occur between individual partners rather than species, and their outcomes determine fitness variation. By examining among-individual variation in interaction niches, we can bridge evolutionary and ecological perspectives to understand interaction biodiversity. This study investigates individual plant variation in frugivore assemblages worldwide, exploring how individual plants “build” their interaction profiles with animal frugivores. Surprisingly, the structure of networks composed of individuals was indistinguishable from networks composed of species. Independently of species or region, interaction frequencies among frugivore partners was highly skewed, with a small subset of species providing most interactions. Additionally, within populations, only a few plants played a key role in attracting a high diversity of frugivores, making them central to the overall network structure.

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Section: Discussionsupporting

confidence: 88%

Downscaling mutualistic networks from species to individuals reveals consistent interaction niches and roles within plant populations

Quintero,

Arroyo-Correa,

Isla

et al. 2024

Preprint

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Vertically stratified interactions of nectarivores and nectar‐inhabiting bacteria in a liana flowering across forest strata*

Thiel,

Gottstein,

Heymann

et al. 2024

American J of Botany

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PremiseVertical stratification is a key feature of tropical forests and plant–frugivore interactions. However, it is unclear whether equally strong patterns of vertical stratification exist for plant–nectarivore interactions and, if so, which factors drive these patterns. Further, nectar‐inhabiting bacteria, acting as “hidden players” in plant–nectarivore interactions, might be vertically stratified, either in response to differences among strata in microenvironmental conditions or to the nectarivore community serving as vectors.MethodsWe observed visitations by a diverse nectarivore community to the liana Marcgravia longifolia in a Peruvian rainforest and characterized diversity and community composition of nectar‐inhabiting bacteria. Unlike most other plants, M. longifolia produces inflorescences across forest strata, enabling us to study effects of vertical stratification on plant–nectarivore interactions without confounding effects of plant species and stratum.ResultsA significantly higher number of visits were by nectarivorous bats and hummingbirds in the midstory than in the understory and canopy, and the visits were strongly correlated to flower availability and nectar quantity and quality. Trochiline hummingbirds foraged across all strata, whereas hermits remained in the lower strata. The Shannon diversity index for nectar‐inhabiting bacterial communities was highest in the midstory.ConclusionsOur findings suggest that vertical niche differentiation in plant–nectarivore interactions seems to be partly driven by resource abundance, but other factors such as species‐specific preferences of hummingbirds, likely caused by competition, play an important role. We conclude that vertical stratification is an important driver of a species’ interaction niche highlighting its role for promoting biodiversity and ecosystem functioning.

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Trait matching without traits: using correspondence analysis to analyze the latent structure of interaction networks

Nicvert,

Fritz,

Dray

2024

Preprint

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Species interactions occurring in ecological communities are often represented as networks. The structure of these networks is thought to be linked to species' interaction niches (or Eltonian niches), which are intimately related to the notion of trait matching, which posits that a species interacts preferentially with partners whose traits are complementary to their own. Multivariate methods are commonly used to quantify species environmental niches (or Grinnellian niches). More recently, they have also been used to study the interaction niche, but these methods consider only the niche optimum and require trait data. In this paper, we use the correspondence analysis (CA) framework to study interaction networks and investigate trait matching without requiring traits data, using the notion of latent traits. We use reciprocal scaling, a method related to CA, to estimate niche optima and breadths, defined respectively as the mean and standard deviation of latent traits of interacting partners in CA space. We present the method, test its performance using a simulation model we designed, and analyze a real mutalistic bird-fruits interaction network. The simulation study shows that the method is able to recover niche breadths and optima for data generated with parameters values typical of ecological networks. The bird-fruit network analysis shows strong relationships between species niche optima and niche breadths: a posteriori correlation with species traits suggest that this latent structure is related to measured traits. In this network, birds and plants of intermediate size tend to have the widest niches and birds with pointed wings (preferentially foraging in the canopy) have smaller niches than birds with rounded wings (preferentially foraging in the understory). CA and reciprocal scaling are described as fruitful methods to characterize species interaction profiles, provide an ecologically meaningful graphical representation of interaction niches and allow to explore the effect of latent traits on network structure.

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Vertically stratified frugivore community composition and interaction frequency in a liana fruiting across forest strata

Cited by 3 publications

References 77 publications

Downscaling mutualistic networks from species to individuals reveals consistent interaction niches and roles within plant populations

Downscaling mutualistic networks from species to individuals reveals consistent interaction niches and roles within plant populations

Vertically stratified interactions of nectarivores and nectar‐inhabiting bacteria in a liana flowering across forest strata*

Trait matching without traits: using correspondence analysis to analyze the latent structure of interaction networks

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