Life history and the structure and stability of plant communities

Life history, the pacing of growth, death, dispersal, and reproduction across the life cycle of species, has long been used to classify and differentiate species and to refine predictions on their demographic patterns. This dissertation expands the applications of life history theory to the traditional domain of theoretical ecology, the structure and composition of biological communities. Unlike other mechanisms to explain and predict the stability of communities such as niche partitioning, fitness differences, environmental responses, and direct competitive interaction, a species’ life history can be measured relatively accurately using only a small number of parameters that are often collected in field censuses. Using the familiar language of Matrix Population Models, I will demonstrate that the internal demographic dynamics of populations can influence their impact on larger, diverse communities of multiple species. In the first chapter, I introduce the key parameter for classification of a species’ dynamics in models of life history variation, Ny, the effective population size measured in years. I develop a model of species interaction without direct competition to isolate the effects of life history. I demonstrate how this parameter predicts coexistence timescales for pairwise competition models and governs species richness in models of metacommunities with outside immigration, revealing that life history variation imposes theoretical constraints on species assembly and competition in communities. I also show statistical support for the hypothesis that life history complementarity, a clustering or parity of Ny values in coexisting species, is prevalent across a wide range of sampled populations. In the second, I integrate the mechanisms of niche partitioning and fitness differences into models of variation in life history. I demonstrate how these classical mechanisms can increase persistence times beyond those predicted by life history complementarity alone. I show modeling results for this theoretical framework, and an analytical estimation for competitive ability in limited ranges of fitness variation. This work aims to begin a process of considering life history differences between species in a wider range of ecological models to increase their accuracy and predictive power. The final chapter applies these predictions on life history and community dynamics to a well-studied and heavily censused tree community at Barro Colorado Island, Panama. I construct life history models for each of the 90 most abundant tree species on the island using a mix of adult and sapling censuses, and theory on reproductive allometry in trees. I then utilize these life history models to predict short-term fluctuations in population abundance using minimal parameters. I compare this to previous modeling approaches and demonstrate that, applying the theory of life history variation in ecological communities, models using only census observations can predict short-term dynamics as well as those with fitted, estimated parameters.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Plant Biology

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Jops, Kenneth

Contributors dc:contributor

• O'Dwyer, James P.
• Dalling, Jim
• Rapti, Zoi
• Salguero-Gómez, Rob

• Community Ecology
• Theoretical Ecology
• Plant Biology
• Life History Theory
• Biodiversity
• Ecological Modeling

Statement dc:rights

• Copyright 2025, Kenneth Jops

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/129825

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F129825