Biology subjects

Fant, L.

Publications and source records attributed to Fant, L..

5 recordsLinked to original sources

bioRxiv2026

Ecological predictability emerges at the population level in phytoplankton communities

Predicting the composition and dynamics of ecological communities is challenging because complexity increases rapidly with species richness. A common strategy is to adopt a reductionist framework in which community dynamics are inferred from simpler components, such as population-level parameters or organismal traits. However, it remains unclear at which level of biological organization ecological predictability emerges. Here we experimentally test this reductionist cascade in marine phytoplankton communities. We first ask whether multispecies dynamics can be quantitatively predicted from demographic parameters measured in monocultures and species pairs. We then test whether these predictive parameters can themselves be inferred from organismal traits, focusing on cell size. We find that community composition is highly reproducible and can be accurately predicted from population-level parameters measured in simpler experimental settings. In contrast, these parameters do not show systematic relationships with cell size and cannot be predicted from this commonly used trait. These results demonstrate that ecological predictability emerges at the population level, where demographic parameters capture the combined effects of underlying biological processes, but resist further reduction to simple trait-based descriptions, suggesting that ecological interactions reshape organismal performance across levels of organisation.

ecology↗

bioRxiv2025

Universal sublinear population growth density dependence unrelated to resource limitation

Growth slows as population density increases, sensitively influencing species coexistence, conservation, and resource management. This slowdown is widely attributed to declining per-capita access to energy and nutrients, and standard models of resource-limited growth predict superlinear declines of growth rate with density. However, we observed sublinear declines for 94% of 4,022 bacterial and eukaryotic growth curves. High-resolution experiments with Escherichia coli revealed a two-phase density dependence: a dominant sublinear regime that transitions to superlinear decline only very near population saturation. The sublinear pattern was invariant across initial resource concentrations, ruling out resource depletion as the cause of early slowing. Our results challenge the standard resource-limitation paradigm and identify non-resource inhibitory processes as a widespread and previously unappreciated regulator of population growth.

ecology↗

bioRxiv2025

Label invariance: a guiding principle for ecological models

Ecological models, though diverse in form, are strengthened when they obey guiding principles. We formalize and advocate for a foundational principle we call "label invariance", which says that a models dynamics must remain the same when identical individuals are arbitrarily grouped into distinct sub-populations. This principle is a necessary consequence of trait continuity--the observation that ecological interactions change continuously as organisms become more similar. Violation of label invariance often implies a hidden, intrinsic niche differentiation between species, which may obscure the mechanisms of biodiversity maintenance. We provide a general framework for constructing both deterministic and stochastic models that follow label invariance. We further demonstrate its utility as a complementary, non-statistical tool for empirical model selection. In sum, label invariance provides an important test for evaluating existing ecological models and a guide for developing new ones, promoting clarity in model assumptions from the outset.

ecology↗

bioRxiv2024

Biomass competition unifies individual and community scaling patterns

Both metabolism and growth scale sublinearly with body mass for most species. Ecosystems show the same sublinear scaling between production and total biomass but ecological theory cannot reconcile the existence of these nearly identical scalings at different levels of biological organization. We solve this paradox using marine phytoplankton to connect individual and ecosystem scalings across three orders of magnitude in body size and biomass. Competitive interactions determined by biomass, rather than differences in species size, slow metabolism in a consistent fashion across species that dominates over species-specific peculiarities, resulting in a unique behavior across community compositions. The allometry of ecosystem production thus emerges from this metabolic density-dependence, independently of the equilibrium state or resource regime of the system. Our findings demonstrate the mechanistic basis of ecosystem allometries, unifying aspects of physiology and ecology to explain why growth patterns are so strikingly similar across scales.

ecology↗

bioRxiv2021

Eco-evolutionary dynamics lead to functionally robust and redundant communities

Microbial communities are functionally stable and taxonomically variable: species abundances fluctuate over time and space, while the functional composition is robust and reproducible. These observations imply functional redundancy: the same function is performed by many species, so that one may assemble communities with different species but the same functional composition. The clarity of this observation does not parallel with a theoretical understanding of its origin. Here we study the eco-evolutionary dynamics of communities interacting through competition and cross-feeding. We show that the eco-evolutionary trajectories rapidly converge to a "functional attractor", characterized by a functional composition uniquely determined by environmental conditions. The taxonomic composition instead follows non-reproducible dynamics, constrained by the conservation of the functional composition. Our framework provides a deep theoretical foundation to the empirical observations of functional robustness and redundancy.

ecology↗