Biology subjects

Polazzo, F.

Publications and source records attributed to Polazzo, F..

5 recordsLinked to original sources

bioRxiv2026

Trait-dependent species responses weaken the effects of response diversity on community stability

The diversity of species responses to environmental change (response diversity) is a key mechanism of ecological stability. However, anticipating where strong or weak stabilizing responses emerge is challenging because species responses can depend on the local community and the specific stability metric. Whether species traits can consistently inform on how species respond to disturbances - enabling less context-dependent predictions - remains an open question. To address this gap, we use microcosm experiments on marine phytoplankton to test how response diversity supports multiple aspects of community stability under pulse temperature changes, testing both an increase (heatwave) and a decrease in temperature (coldspell). We then map species traits to their responses in a community to identify which traits modulate and predict species sensitivities. Fundamental response diversity, based on the diversity of species responses to temperature measured in isolation, was a weak predictor of community stability, and relationships differed between disturbances (i.e., heatwave and coldspell). Instead, species traits were consistent predictors of species responses in communities. Small, fast-growing species were more tolerant and benefited from the disturbance, while large, slow-growing species were less tolerant and decreased in proportion - these patterns were consistent across disturbances and community compositions. These results suggest that strong trait-performance relationships might reduce the importance of response diversity for stability. But these findings also show that general species traits, such as size and growth rate, can predict which species, and how, contribute to community responses, providing an empirical basis to relate species traits to stability outcomes under climate change.

ecology↗

bioRxiv2026

Community performance curves predict community stability despite interaction effects

Predicting whether aggregate community properties remain stable as environments fluctuate is a central challenge in ecology. We asked how well species' fundamental niches predict this aspect of community stability. We developed community performance (CP) curves by aggregating species-specific performance across environmental conditions and tested whether their variability explains temporal variability in communities. In Lotka-Volterra and mechanistic consumer-resource simulations, CP variability explained, on average, 89% of variation in total abundance variability, and explanatory power remained above 75% across gradients of interaction strength and coexistence conditions. In a purpose-designed microcosm experiment, CP variability explained 67% of variation in total biomass variability. CP curves thus retain substantial predictive information even in strongly interacting systems, providing a tractable basis for forecasting community stability when species interactions are unknown.

ecology↗

bioRxiv2025

The imbalance of nature: The Role of Species Environmental Responses for Ecosystem Stability

Understanding the mechanisms underlying ecosystem stability is crucial in predicting ecological responses to environmental fluctuations. While the diversity-stability relationship has been widely studied, the role of species fundamental responses to the environment remains underexplored. Here, we investigate how the distribution of fundamental responses, captured by a novel metric--imbalance--drives ecosystem stability through asynchrony and population stability. Using a microcosm experiment with protist communities, we manipulated species richness and response distributions (defined as interspecific variation in species performance curves) under fluctuating temperature and different nutrient concentrations. Our results show that lower imbalance, achieved through asynchrony or high population stability, causes higher temporal stability, while richness has no effect on stability. Structural equation modelling revealed that imbalance decreases stability indirectly via increasing synchrony and decreasing population stability, explaining 90% of observed variation. Comparing imbalance derived from single versus multispecies communities demonstrates that fundamental species responses are primary drivers of stability, challenging traditional paradigms emphasizing interspecific interactions. This study provides mechanistic links between species responses, environmental variability, and ecosystem stability, offering new insights into the responses of ecological systems to environmental change.

ecology↗

bioRxiv2023

Response diversity in the context of multifarious environmental change

1.Response diversity represents the inter- and intraspecific trait variation in organismal responses to the environment. Assemblages composed of organisms displaying large variation in their response to the environment (that is, having high response diversity) are expected to have higher temporal stability of aggregate community and ecosystem properties such as ecosystem functioning (i.e., an insurance effect). Yet, response diversity is not commonly measured in empirical studies, and when it is measured, this is done in different ways. Moreover, most proposed measures of response diversity concern situations with only one driver of environmental change. Thus far, no specific approach exists to measure response diversity in the context of multiple simultaneously changing (multifarious) environmental drivers. Here, we propose a new method to empirically quantify response diversity in the context of multifarious environmental change. First, we illustrate this method using simulated data. Next, we reveal the role of the direction of environmental change in shaping response diversity when multiple drivers of environmental change fluctuate over time. We show that, when the direction of the environmental change is unknown (that is, there is no information or a priori expectation about how an environmental condition has changed or will change in future), we can quantify the potential response diversity for a given community under any possible future environmental change scenario. That is, we can estimate the potential response capacity of a system under a range of extreme or realistic environmental changes, capturing its complete insurance capacity, with utility for predicting future responses to even multifarious environmental change. Finally, we investigate the drivers of response diversity in a multifarious environmental change context, showing how response diversity depends on: 1) the diversity of species responses to each environmental variable considered, 2) the relative effect of each environmental variable on species performance, 3) the correlation between the diversity in species responses to different environmental variables, and 4) the mean temporal value of the environmental variable. In doing so, we take an important step towards understanding the insurance capacity of ecological communities exposed to multifarious environmental change.

ecology↗

bioRxiv2020

Changes in community composition determine recovery trajectories from multiple agricultural stressors in freshwater ecosystems

Pesticides have been identified worldwide as a threat for aquatic biodiversity due to their widespread use in agriculture and their capacity to reach freshwater ecosystems. Very little is known about the consequences of pesticide mixtures targeting different organism groups on community dynamics. Especially, how horizontal changes within one trophic level are propagated vertically across the food web has been rarely investigated. To get insight on the effects of pesticide mixtures on community dynamics, we performed a mesocosm experiment manipulating three common agricultural stressors: chlorpyrifos (an insecticide), diuron (an herbicide) and nutrients. The results of this study show that all stressors had significant effects on community composition, species richness and abundance. However, recovery trajectories and ecosystem functioning effects largely depended on the type of stressor as well as on post-disturbance trophic and non-trophic interactions. Effects of pesticides were generally recovered by the end of the experimental period when considering abundance, whereas community composition further departed from control systems. High nutrient loads led to a shift in community composition characterized by high taxa dominance and lower species richness, which in turn contributed to increased total organism abundance and reduced recovery times to pesticide exposure. We found interactions between the tested stressors to be significant only few times at the community level, while interactions were more common at the population level. Our findings indicate that management of freshwater ecosystems should consider pre-disturbance community composition and long-term changes in interactions across different organism groups to set effective protection measures.

ecology↗