Niche Theory for Mutualism: A Graphical Approach to Plant-Pollinator Network Dynamics

Abstract

Contemporary Niche Theory is a useful framework for understanding how organisms interact with each other and with their shared environment. Its graphical representation, popularized by Tilman's Resource Ratio Hypothesis, facilitates the analysis of the equilibrium structure of complex dynamical models including species coexistence. This theory has been applied primarily to resource competition since its early beginnings. Here, we integrate mutualism into niche theory by expanding Tilman's graphical representation to the analysis of consumer-resource dynamics of plant-pollinator networks. We graphically explain the qualitative phenomena previously found by numerical simulations, including the effects on community dynamics of nestedness, adaptive foraging, and pollinator invasions. Our graphical approach promotes the unification of niche and network theories, and deepens the synthesis of different types of interactions within a consumer-resource framework.

Ecological theory of mutualism: Robust patterns of stability and thresholds in two‐species population models

“…Additionally, species are likely to have critical (cumulative) thresholds to allow population growth. For example, Valdovinos and Marsland ( 2021 ) identify the quality of visits needed from pollinators for plants to persist. Below such threshold, the plant species and the animals depending on those plants go extinct.…”

Simple mechanisms of plant reproductive benefits yield different dynamics in pollination and seed dispersal mutualisms

“…Most recently, Revilla (2015) predicts threshold effects in obligate plants, in which plants at low density cannot recover fast enough to save their animal partners from decline, even if the animal population was originally at very high density. Finally, Valdovinos and Marsland (2021) identify the quality of visits needed from pollinators for plants to persist. Below such threshold, the plant species and the animals depending on those plants go extinct.…”

“…More recent research advanced upon these phenomenological representations of mutualism by developing models that account for consumer-resource mechanisms (Wright 1989, Holland & DeAngelis 2010, Valdovinos et al 2013, Revilla 2015. Accounting for consumer-resource mechanisms enabled the discovery of important dynamics, such Allee effects, alternative states, transitions between mutualism and parasitism, competition among species sharing mutualistic partners, and niche partitioning (May 1976, Soberón & Martinez del Rio 1981, Wells 1983, Wright 1989, Pierce & Young 1986, Holland & DeAngelis 2010, Valdovinos et al 2013, Revilla 2015, Valdovinos & Marsland 2021 as well as the integration of these mutualisms into food web dynamics (Hale et al 2020). This research, however, mostly focused on animal dynamics (i.e., the consumer) and the dynamics of plant resources available to the animals (but see Wells 1983).…”

Flowering overlap and floral trait similarity help explain the structure of pollination networks

“…ited by less than 10% of the pollinator species (see Figure S5). This pattern could be due to increased competition for pollinators, which would lead to low pollinator sharing and more specialized plant-pollinator interactions (see Valdovinos & Marsland, 2021;Wei et al, 2021). The sand dune has been described as a community characterized by limited pollinator activity and high plant competition for pollinators (Albor et al, 2020;Parra-Tabla et al, 2019).…”

“…Specifically, the level of plant generalization with respect to floral visitors (i.e. the number of pollinator species associated with a single plant; plant generalization hereafter) and the degree of pollinator sharing with other plant species may influence patterns of network nestedeness and modularity, two main descriptors of plant-pollinator network structure (Petanidou et al, 2008;Valdovinos & Marsland, 2021).…”