bioRxiv Science⌕ Search

Biology subjects

Rohwer, F. L.

Publications and source records attributed to Rohwer, F. L..

2 recordsLinked to original sources

Emerging dynamic regimes and tipping points from finite empirical principles

The dynamics of biogeochemical, ecological, and astronomical systems are transient. Yet, predicting the occurrence of dynamical shifts remains a challenge due to inferential uncertainties from datasets and the limitations of asymptotic-dependent theories. To address this problem, we developed a theoretical framework that builds on the finite nature of observations. This framework assesses the relative importance of processes, defined as the mechanisms that contribute to the rate of change of the systems dynamic variables, and it predicts the critical values that would trigger a shift into a new regime. The number of observable dynamic regimes within the framework increases exponentially with the number of processes. Observers, however, only experience dynamic regimes associated with relevant processes-- those exceeding a tipping point--within their reference framework. A case study of the framework was tested for a classic predator-prey system with four processes parameterized for bacteria (prey) and lytic bacteriophages (predator). The analysis recovered the sixteen dynamic regimes predicted by the framework, including two non-trivial quasi-equilibrium dynamics. An adaptive Boolean model, which used only relevant observable processes, validated the accuracy of the framework, recovering the dynamics of the full model. The observational framework introduced here provides a strategy for identifying the processes and conditions that lead to tipping points, representing a conceptual paradigm shift in transient dynamics, placing the focus on the specific, finite context of the observer, rather than the intrinsic, asymptotic states of the system. SIGNIFICANCESudden shifts in ecological, climate, and biological systems--so-called tipping points or critical transitions--are notoriously difficult to predict. This study introduces a mathematical framework that redefines these transitions as outcomes shaped by the observers empirical limits. By accounting for finite observation time and resolution, the framework uncovers a rich spectrum of dynamic regimes that classical theories overlook. Its conceptual rigor and practical value are demonstrated in a predator-prey system. This new approach reframes how to forecast regime shifts in complex systems and offers a tool with broad relevance, from microbial ecosystems to planetary climate.

ecology↗

Relevance of coral geometry in the outcomes of the coral-algal benthic war

Corals have built reefs on the benthos for millennia, becoming an essential element in marine ecosystems. Climate change and human impact, however, are favoring the invasion of non-calcifying benthic algae and reducing coral coverage. Corals rely on energy derived from photosynthesis and heterotrophic feeding, which depends on their surface area, to defend their outer perimeter. But the relation between geometric properties of corals and the outcome of competitive coral-algal interactions is not well known. To address this, 50 coral colonies interacting with algae were sampled in the Caribbean island of Curacao. 3D and 2D digital models of corals were reconstructed to measure their surface area, perimeter, and polyp sizes. A box counting algorithm was applied to calculate their fractal dimension. The perimeter and surface dimensions were statistically non-fractal, but differences in the mean surface fractal dimension captured relevant features in the structure of corals. The mean fractal dimension and surface area were negatively correlated with the percentage of losing perimeter and positively correlated with the percentage of winning perimeter. The combination of coral perimeter, mean surface fractal dimension, and coral species explained 19% of the variability of losing regions, while the surface area, perimeter, and perimeter-to-surface area ratio explained 27% of the variability of winning regions. Corals with surface fractal dimensions smaller than two and small perimeters displayed the highest percentage of losing perimeter, while corals with large surface areas and low perimeter-to-surface ratios displayed the largest percentage of winning perimeter. This study confirms the importance of fractal surface dimension, surface area, and perimeter of corals in coral-algal interactions. In combination with non-geometrical measurements such as microbial composition, this approach could facilitate environmental conservation and restoration efforts on coral reefs.

ecology↗