Understanding spatial and temporal dynamics in single-species systems: Implications for ecosystem stability and biodiversity conservation
Abstract: Biodiversity is a crucial prerequisite for the functioning of natural communities and ecosystems. However, the immense biodiversity in aquatic systems still raises many unresolved questions for ecologists. How can so many species coexist with only a few limited resources? This question was initially addressed by models and later by experiments showing that non-linear dynamics (interactions which do not follow linear trends) can generate complex behaviours, including oscillations and deterministic chaos, which allow multiple species to coexist where traditional linear models predict competitive exclusion. Deterministic chaos describes aperiodic fluctuations highly sensitive to initial conditions and is, without mathematical methods, barely distinguishable from random fluctuations. However, its underlying order providing ecosystem stability and ranges in which organisms abundances fluctuate, unlike pure stochasticity. Whilst models and experiments have demonstrated the potential of non-linear and chaotic dynamics to explain biodiversity patterns, the underlying mechanisms and reasons for chaos have remained elusive. This gap in understanding is not due to the absence of such dynamics in nature, but rather the complexity of natural systems and the challenge in isolating intrinsic factors from external influences make it difficult to recognise this phenomenon. Long-term, high-resolution data collection under tightly controlled conditions is necessary to distinguish deterministic chaos from random fluctuations and to uncover the intrinsic mechanisms driving dynamics. Such experiments are challenging to conduct and interpret, but are crucial for understanding the fundamental processes that contribute to biodiversity.
Our results show that even single-species populations exhibit characteristics of non-linear and chaotic dynamics. Using an automatic cell registration system, we conducted a continuous and undisturbed analysis of dynamic behaviour of a chemostat with high temporal resolution. Additionally, we performed experiments using a microfluidic chip, which in addition to chaotic dynamics also revealed self-organised patterns in a spatial dimension. These findings demonstrate that complex processes occurring within individual cells can significantly influence dynamics at both the population and spatial levels, challenging the traditional view that non-linear dynamics primarily arise from interactions between different species and as a response to interactions with the environment. Our findings reveal that single-species dynamics often operate at the “edge of chaos”, a state characterised by a mixture of chaotic, ordered and stochastic disordered behaviour, which may be particularly important for ecosystem resilience. Studying non-linear dynamics is crucial as it provides insights into the mechanisms that maintain biodiversity in natural ecosystems, even in wastewater treatment such pattern have been observed. Also, chaotic dynamics and pattern formation can stabilise ecosystems by reducing extinction rates and allowing a higher diversity, implications which can be explained by the behaviour of single-species dynamics as visible in our experiment. Hopefully, this study can bridge the gap between theoretical models and experimental observations, underscoring the importance of considering non-linear dynamics in both basic research and applied fields of ecology.
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