4C: Bringing theoretical ecology into practice.

4C: Bringing theoretical ecology into practice

Conveners:     Geerten Hengeveld (Netherlands Institute of Ecology)

                       Sven Teurlincx (Netherlands Institute of Ecology)

1. Susceptibility of complex ecosystems to interaction timing

Jilles Verwoerd, Phillip Staniczenko, and Debabrata Panja, Utrecht University

Interactions amongst species are temporally constrained since two species can interact only if they are present at the same time. However, ecological models that describe community dynamics typically ignore these — i.e., co-presence — constraints. Here we show how to estimate the co-presence constraints from empirical data and present a general approach to incorporating them into existing community dynamics models. With this addition, one can study the impacts of changes in co-presence on community dynamics. Focusing on mutualistic plant-pollinator systems as an application area, we showcase that incorporating co-presence constraints in the models leads to significant changes in the distribution of interaction strength estimates, altering our understanding of key interactions and species in a community. We also demonstrate how our approach can assess the susceptibilities of individual species and communities to changes in co-presence due to changes in phenology induced by, e.g., climate and land-use changes.

2. Temporal origin of nestedness in plant-pollinator networks

Deb Panja, Phillip Staniczenko, Utrecht University

Nestedness is a common property of mutualistic networks. In networks with high levels of nestedness, the link positions of low-degree nodes (those with few links) form nested subsets of the link positions of high-degree nodes (those with many links), leading to matrix representations with characteristic upper triangular or staircase patterns. Recent theoretical work has suggested that nestedness is a structural by-product of the skewed degree distributions often found in plant-pollinator interactions data. However, mechanisms for generating nestedness remain poorly understood. We show that a simple probabilistic model based on phenology – the timing of copresences among interaction partners – can produce nested structures and correctly predict around one-third of interactions in 22 plant–pollinator networks. Notably, the links most readily explained by frequent actor copresences appear to form a backbone of nested interactions, with the remaining interactions attributable to opportunistic interactions or preferences for particular interaction partners that are not routinely available.

3. Generational conflicts shape the abundance, structure and dynamics of Arctic char populations

André M. de Roos, Sven Norman, Karin A. Nilsson & Pär Byström, University of Amsterdam 

A unique feature of fish life history is that individuals grow through large body size ranges between birth and adulthood. As a consequence, individuals often change diet while growing, which changes to what extent they compete with differently sized conspecifics for limiting resources. Furthermore, cannibalism of larger adults on small juveniles occurs frequently. Juveniles hence interact with a different ecological environment than adults, which gives rise to a potential parent-offspring conflict. Selection favours adults to increase reproduction as much as possible, which however leads to more intense competition among their offspring. Vice versa, when juveniles do well and mature in large numbers, competition among adults is intensified. Using a size-structured population model I will show how this intergenerational conflict shapes the body size distribution, dynamics and abundance of Arctic char populations and its implications for ecosystem functioning, such as the extent to which populations yield harvestable biomass.

4. The ecosystem resilience approach of established invasive tree species

Lisa Raats & Bart Nyssen, KU Leuven & Bosgroep Zuid Nederland

Invasive tree species pose a global threat to forest ecosystems' characteristic biodiversity. Disturbances, such as logging and forest restoration activities, create open niches that allow invasive tree species to establish and dominate. Once a large population of invasive tree species is established, eradication often becomes unsuccessful and costly, underscoring the need for practical, cost-effective alternatives.

The Ecosystem Resilience Approach (ERA) focuses on reducing the forest ecosystem invasibility by established invasive tree species (EITS) by enhancing tree and shrub species diversity and redundancy without prior reduction of EITS biomass.

Our results demonstrate that introducing native species enhances the resilience of forest ecosystems against invasions, as evidenced by the decrease in EITS. This effectiveness of the ERA was confirmed by global collaboration with researchers who conducted similar studies, enhancing our findings' credibility. Therefore, we conclude that ERA offers a promising and practical solution to reduce the invasibility of forest ecosystems by EITS.

5. Digital twins in ecology – a theoretical ecology view

Geerten Hengeveld, Sven Teurlincx, Netherlands Institute of Ecology

Digital twins provide a new paradigm for digitally representing physical systems – especially for ecological systems. Most ideas of digital twins include model and data integration to provide a towards-continuous - spatial and temporal – historic and future - best estimate of ‘the’ state of the ecosystem. This concept includes theoretical ecology components interwoven with components from datascience, computerscience and machine learning, linked to a specific information request.

For ecology thinking in terms of digital twins could provide three major benefits (1) it can provide an approach to support interaction between different fields of ecology – and test hypotheses about these interactions, (2) it can provide a new view on data availability and (3) it can provide access to tools from datascience, computerscience and machine learning that are currently less accessible for the average ecologist.

Based on the previous presentations, we will explore how the developing digital twins of ecosystems with the support of theoretical ecologists can further ecological research.