arXiv subjects

Mozzamil Mohammed

Publications and source records attributed to Mozzamil Mohammed.

3 recordsLinked to original sources

arXiv2026

Long-term Coexistence of Epidemics and Risk Awareness: Impacts of Adaptive Human Response and Fatigue

Human behavior shapes epidemic dynamics, yet most models represent it by rescaling the transmission rate, which conflates behavior with biology and fails to capture the memory associated with sustained protective behavior. We develop and analyze a susceptible-infected-recovered-aware model in which awareness is generated by prevalence and eroded by fatigue. Rather than modifying transmission probabilities, awareness moves susceptible and infectious individuals between accessible and inaccessible compartments. The basic reproduction number is independent of all behavioral parameters, showing that awareness cannot directly alter invasion. A unique endemic equilibrium exists exactly when the basic reproduction number is greater than one, thereby excluding backward bifurcation. Infection and awareness are uniformly persistent, ensuring robust coexistence. We derive an exact decomposition of the reduction in endemic burden into contributions from susceptible withdrawal and infectious sequestration, determine the effect of each behavioral parameter, and show that the endemic state depends on awareness response and fatigue only through their ratio. In addition, prevalence vanishes linearly as fatigue approaches zero. In the limit of instantaneous behavioral relaxation, the model reduces to the classical transmission-modulating formulation, whose endemic equilibrium is always stable. At finite relaxation rates, however, accessibility can destabilize the endemic equilibrium through a Hopf bifurcation, generating self-sustained epidemic cycles without any imposed delay.

physics.soc-ph↗

arXiv2024

Coexistence via trophic cascade in plant-herbivore-carnivore systems under intense predation pressure

Carnivores interact with herbivores to indirectly impact plant populations, creating trophic cascades within plant-herbivore-carnivore systems. We developed and analyzed a food chain model to gain a mechanistic understanding of the critical roles carnivores play in ecosystems where plants face intense herbivory. Our model incorporates key factors such as seed production rates, seed germination probabilities, local plant interactions, herbivory rates, and carnivore predation rates. In the absence of carnivores, herbivores significantly reduce plant densities, often driving plants to extinction under high herbivory rates. However, the presence of carnivores suppresses herbivore populations, allowing plants to recover from herbivore pressure. We found that plant densities increase with carnivore predation rates, highlighting top-down effects and underscoring the importance of conserving carnivores in ecosystems where plants are at high risk of extinction from herbivory. Our results also show that carnivore density increases with seed-production rates, while herbivore density remains constant, indicating that plants benefit carnivores more than herbivores. This increase in carnivore density driven by high seed-production rates reflects bottom-up effects in the system. Overall, our study demonstrates that plants, herbivores, and carnivores can coexist even under intense predation stress. It suggests that carnivores play a crucial role in regulating plant and herbivore populations, with significant potential for maintaining biodiversity within ecosystems.

q-bio.PE↗

arXiv2023

Fruit harvesting: A potential threat to the persistence, spatial distribution, and establishment of plants

Plant-frugivore interactions play a central role for plant persistence and spatial distribution by promoting the long-range dispersal of seeds by frugivores. However, plant-frugivore interactions are increasingly being threatened by anthropogenic activities. An important anthropogenic threat that could expose plant-frugivore systems to extinction risk is fruit harvesting. Here, we develop an individual-based and a pair-approximation model of plant-frugivore-human interactions to elucidate the effects of human harvesting of fruits on plant establishment, persistence, and spatial distribution. Our results show that frugivores strongly affect global density of plants and gradually shift their spatial distribution from aggregated to random, depending on the attack rate and dispersal efficiency of frugivores. We find that, in the absence of frugivores, plants experiencing intense fruit harvesting cannot persist even if their fecundity is high. In the presence of frugivores, fruit harvesting profoundly affects the global dispersal of seeds and thus changes the spatial distributions of plants from random to aggregated, potentially causing plant extinction. Our results demonstrate that sufficiently efficient frugivores mitigate the negative impact of fruit harvesting on plant populations and enable plant establishment precluded by harvesting. Taken together, these results draw attention to previously underappreciated impacts of fruit harvesting in plant-frugivore-human interactions.

q-bio.PE↗