Mosquitofish in contrasting environments, symbolizing divergent evolutionary paths.

Unlocking the Secrets of Survival: How Ecosystems Shape Behavior and Lifespan

Lena Kashyap in Science & Nature September 2025 • 4 min read.

"New research reveals the surprising ways ecological conditions mold animal behavior, physiology, and life history, challenging long-held assumptions about adaptation."

For decades, scientists have explored the pace-of-life syndrome (POLS), a concept suggesting that an individual's behavior and physiology are intricately linked to their life history. The theory proposes that individuals on the 'fast' end of the spectrum grow quickly, take more risks, exhibit higher metabolism, but face a shorter lifespan. Conversely, those on the 'slow' end develop more deliberately, are risk-averse, conserve energy, and live longer. However, empirical evidence supporting this theory has been inconsistent, leading researchers to question whether POLS is a fixed construct or a product of specific environmental pressures.

Recent modeling studies indicate that the expression of POLS can vary significantly along selection gradients, highlighting the importance of ecological variation in shaping these syndromes. This variability underscores the need to consider the external conditions that might influence the relationships between life history, physiology, and behavior. Is an organism's destiny predetermined, or can ecological factors tilt the scales?

A groundbreaking study on two populations of Eastern mosquitofish sought to address this question by examining how differing ecological conditions influence the development of POLS traits. By comparing fish from distinct environments and analyzing their life histories, behaviors, and physiological traits under identical laboratory settings, scientists aimed to uncover whether POLS is a rigid framework or a flexible response to environmental demands.

Ecosystems as Sculptors: How Environment Shapes Life Strategies

Mosquitofish in contrasting environments, symbolizing divergent evolutionary paths.

The study focused on two mosquitofish populations from Italy: one from the stable, sheltered environment of Torre Castiglione's sinkhole, and the other from the fluctuating, resource-scarce pond in Maccarese. These environments presented stark contrasts in temperature stability, predation risk, and resource availability. The researchers hypothesized that these differences would lead to divergent life-history strategies in the fish, detectable even when raised in a controlled laboratory setting.

Under controlled lab conditions, the mosquitofish exhibited strikingly different life histories. The Maccarese population (FG), adapted to a harsh, resource-limited environment, matured quickly and reproduced earlier. In contrast, the Torre Castiglione population (SG), hailing from a stable, predator-free habitat, grew more slowly, reached larger sizes, and invested more in muscle development. These findings suggest that environmental pressures leave an indelible mark on a population’s life strategy.

Differential Investments: The fast-growing FG population prioritized early reproduction, while the slow-growing SG population focused on growth and physical development.
Behavioral Divergence: SG fish were bolder, more active, and had higher metabolic rates than their FG counterparts.
Inconsistent Correlations: The correlation structures among POLS traits differed between the populations, with POLS expression observed mainly in the slow-growing SG population.

Interestingly, the study revealed that SG fish were bolder (exhibited shorter latency to emerge from a refuge), more active (spent less time freezing and traveled longer distances), and had higher standard metabolism. This suggests that in stable environments, risk-taking and high energy expenditure may be viable strategies. However, these correlations were not consistent across both populations, challenging the universality of POLS.

The Future of POLS Research: Embracing Complexity and Context

These findings suggest that POLS traits can evolve independently, and their coevolution depends on specific ecological processes. Environmental pressures, such as predation risk and resource availability, can sculpt life-history strategies and influence the relationships between behavior, physiology, and lifespan. Ultimately, understanding the intricate interplay between ecological conditions and evolutionary processes is crucial for unraveling the complexities of animal adaptation and the pace-of-life syndrome.

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This article is based on research published under:

DOI-LINK: 10.1038/s41598-018-33047-0, Alternate LINK

Title: Ecological Conditions Drive Pace-Of-Life Syndromes By Shaping Relationships Between Life History, Physiology And Behaviour In Two Populations Of Eastern Mosquitofish

Subject: Multidisciplinary

Journal: Scientific Reports

Publisher: Springer Science and Business Media LLC

Authors: Giovanni Polverino, Francesca Santostefano, Carlos Díaz-Gil, Thomas Mehner

Published: 2018-10-02

Everything You Need To Know

What is the Pace-of-Life Syndrome (POLS), and what key aspects does it encompass?

The Pace-of-Life Syndrome (POLS) suggests that an individual's behavior and physiology are intricately linked to their life history. Individuals on the 'fast' end grow quickly, take more risks, and exhibit higher metabolism but have shorter lifespans. Conversely, those on the 'slow' end develop deliberately, are risk-averse, conserve energy, and live longer. However, the expression of POLS can vary significantly based on ecological conditions, which means external conditions influence the relationships between life history, physiology, and behavior. This variation challenges the idea that POLS is a fixed construct, indicating that environmental pressures play a crucial role in shaping these syndromes. Considering ecological factors is essential to understanding the complexities of POLS.

How did the study of mosquitofish populations in different Italian ecosystems contribute to understanding the Pace-of-Life Syndrome?

The study on Eastern mosquitofish compared two populations from Italy: one from Torre Castiglione's stable sinkhole (SG) and another from Maccarese's fluctuating pond (FG). The Torre Castiglione population (SG), from a stable, predator-free habitat, grew slowly, reached larger sizes, and invested more in muscle development. The Maccarese population (FG), adapted to a harsh environment, matured and reproduced early. In lab conditions, the Torre Castiglione fish (SG) were bolder and more active with higher metabolism, while the Maccarese fish (FG) prioritized early reproduction. This demonstrates how environmental pressures shape life-history strategies, challenging the universality of Pace-of-Life Syndrome and showing that its traits can evolve independently based on ecological processes.

What were the main differences observed between the mosquitofish populations from Torre Castiglione (SG) and Maccarese (FG) when raised in a controlled lab environment?

In a controlled lab environment, the mosquitofish from Torre Castiglione (SG) grew more slowly, reached larger sizes, and invested more in muscle development compared to the Maccarese (FG) population. Behaviorally, the Torre Castiglione fish (SG) were bolder, more active, and had higher standard metabolism, meaning they were more willing to take risks and expend more energy. The Maccarese population (FG), on the other hand, matured quickly and reproduced earlier, reflecting their adaptation to a resource-limited environment. These differences highlight that environmental pressures leave a significant mark on a population's life strategy and that traits associated with the Pace-of-Life Syndrome (POLS) can vary based on ecological context.

What implications does the variability of Pace-of-Life Syndrome (POLS) have for understanding animal adaptation and evolution?

The variability of Pace-of-Life Syndrome (POLS) implies that animal adaptation and evolution are heavily influenced by specific ecological processes. Environmental pressures, such as predation risk and resource availability, can shape life-history strategies and the relationships between behavior, physiology, and lifespan. The finding that POLS traits can evolve independently challenges the idea of a universal, fixed syndrome. Understanding the complex interplay between ecological conditions and evolutionary processes is crucial for unraveling the complexities of animal adaptation. Organisms' destinies are not predetermined; ecological factors can significantly influence their traits and strategies. This perspective is vital for comprehending how animals adapt to diverse and changing environments.

How do ecological factors influence the expression and coevolution of Pace-of-Life Syndrome (POLS) traits, and why is this understanding important?

Ecological factors, such as predation risk and resource availability, play a crucial role in shaping the expression and coevolution of Pace-of-Life Syndrome (POLS) traits. Environmental pressures can sculpt life-history strategies and influence the relationships between behavior, physiology, and lifespan. The study of mosquitofish demonstrates that POLS traits can evolve independently, and their coevolution depends on specific ecological processes. Understanding this intricate interplay is essential for unraveling the complexities of animal adaptation. Recognizing that ecological context can significantly influence an organism's traits is vital for comprehending how animals adapt to diverse environments. The findings suggest the expression of POLS can vary significantly, underscoring the need to consider the external conditions that might influence the relationships between life history, physiology, and behavior.