Biology subjects

Ostling, A.

Publications and source records attributed to Ostling, A..

2 recordsLinked to original sources

bioRxiv2025

Influence of natural enemy specificity and functional response on victim coexistence

Natural enemies are thought to promote coexistence of competing victim species. Although existing theory suggests victim coexistence increases with enemy specialization, the dynamics and potential extinction of enemies is generally discounted. Where enemy dynamics have been considered, empirically atypical linear functional responses have been studied. These limitations could over-simplify inferences about enemy-mediated coexistence. We studied the dynamics of two competing victim species and two enemy species with a deterministic model. We derived equilibrium points, and used linear stability analysis, numerical simulations and Floquet theory to determine the influence of enemy specificity and non-linear functional responses on coexistence in this victim-enemy community. We found greater specificity could drive enemy equilibrium points to infeasible values. We found only accelerating enemy functional responses result in stable equilibrium point coexistence of otherwise equivalent competitor victims, in which case greater specificity results in greater stability. Linear and saturating responses produce complex dynamics (neutral or limit cycles, chaos) or extinction, with limit cycle stability highest at intermediate specificity. Our results indicate strict specificity may not maximize coexistence, and enemy functional response critically influences whether enemies promote victim coexistence. They highlight the need to incorporate enemy dynamics into the growing body of theory regarding enemy-mediated diversity maintenance.

ecology↗

bioRxiv2023

Disturbance-generated competitive coexistence

Explaining how competing species coexist remains a challenge in ecology. A major hypothesis is that disturbance opens up the opportunity for types with different "life history" strategies to coexist, allowing types better at getting to and using recently disturbed patches to coexist with better competitor types. A simple model introduced several decades ago demonstrated this, but its focus on patch dynamics (i.e. the dynamics of the number of patches a species occupies) gives limited insight into how coexistence-enabling variation arises from within-patch demographic strategies. Here we present, and demonstrate how to analyze, a partial differential equation model that captures the emergence of larger-scale competitive dynamics from within-patch population dynamics of species competing for patches subject to disturbance. We analyze key cases of the model framework, with competition acting in turn on each aspect of within-patch demography included in the model: reproduction, offspring-survival, and adult-survival. Insights arising from these analyses include: 1) variation between species on a simple reproduction-adult-survival trade-off can enable disturbance-generated coexistence, 2) variation along trade-offs with species robustness-to-competition can also generate coexistence 3) disturbance-generated coexistence may or may not involve classical "successional dynamics" within patches, and 4) coexistence is easier to generate at intermediate disturbance rates. Our work here provides new tools for more complete development of the theory of disturbance-generated coexistence.

ecology↗