Biology subjects

Mazzarisi, O.

Publications and source records attributed to Mazzarisi, O..

4 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

A balance between environmental filtering and competitive exclusion modulates the macroecology of alternative stable states in microbial communities

Predicting the assembly and stability of microbial ecosystems is fundamentally challenged by the stochas-ticity inherent in historical contingencies. Although these dynamics often appear reproducible at coarse taxonomic or functional scales, the mechanisms governing fine-grained species-level variation and the emergence of alternative stable states remain an unresolved problem in ecology. Bridging the gap between individual species variability and the emergence of predictable community-level attractors is essential for a mechanistic understanding of ecosystem resilience. Here, by analyzing replicate microbial communities assembled in vitro, we demonstrate that community structure is built upon individual species exhibiting robustly bimodal abundance distributions. Each taxon exists in either a high- or low-abundance state. We show that the collective configuration of these binary species states--a phenomenon also observed in natural systems--drives the correlation structure between community members and defines a set of discrete, alternative community-level attractors. By examining the prevalence of species across these attractors, we uncover a striking taxonomic signal: phylogenetically close relatives are significantly more likely to display reciprocal prevalence patterns--where the dominance of one relative necessitates the suppression of the other--than expected by chance. This discovery directly rejects models based on simple functional redundancy. Instead, it proves that state-dependent competitive exclusion is a primary driver of community divergence, where the identity of the "winner" is contingent on the collective state of the entire community. Our work reframes microbial community structure through the lens of discrete population states, providing a predictive framework for understanding ecosystem stability and the engineering of community functions.

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↗