An Individual-Based Model (IBM) was developed by employing natural and toxic survival rates of individuals to elucidate the community responses of benthic macroinvertebrates to anthropogenic disturbance in the streams. Experimental models (doseresponse and relative sensitivity) and mathematical models (power law and negative exponential distribution) were applied to determinate the individual survival rates due to acute toxicity in stressful conditions. A power law was additionally used to present the natural survival rate. Life events, covering movement, exposure to contaminants, death and reproduction, were simulated in the IBM at the individual level in small (1 m) and short (1 week) scales to produce species abundance distributions (SADs) at the community level in large (5 km) and long (1~2 years) scales. Consequently, the SADs, such as geometric series, log-series, and log-normal distribution, were accordingly observed at severely (Biological Monitoring Working Party (BMWP⁄10), intermediately (BMWP⁄40) and weakly (BMWP›50) polluted sites. The results from a power law and negative exponential distribution were suitably fitted to the field data across the different levels of pollution, according to the Kolmogorov-Smirnov test. The IBMs incorporating natural and toxic survival rates in individuals were useful for presenting community responses to disturbances and could be utilized as an integrative tool to elucidate community establishment processes in benthic macroinvertebrates in the streams.

Stream and river habitats are characterized by a uni-directional water flow. Organisms colonizing such habitats are faced with the constraint of continuous downstream flow. Some ecologists find it puzzling that upstream is colonized by insect communities although the insects are continuously faced with downstream flow. The obvious solution to the puzzle is that there exist compensatory strategies, three of which have gained some notoriety in recent years: 1) diffusive random movement and density-dependent regulation of population size; 2) daily directed movement during larvae stage; 3) the compensation of larval drift by adult upstream flight. We have adapted an eco-evolutionary individual-based model (IBM) to accommodate typical life events of aquatic insects, such as birth, death, diffusion, and drifting. The probabilities of these events, which occur on the individual level, depend on both biological (e.g., local competition, upstream flight by adult insects) and environmental (e.g., unidirectional flow) constraints. The evolution of selected traits, namely, adapted water velocity, drifting time and distance, and upward flight distance, was investigated through simulation. We find that, while the three strategies are generally able to sustain upstream populations, the exact compensation of drift loss allowed by upstream flight makes the third strategy less “asteful” a population of upstream flight strategists to outcompete diffusive movement strategists. We also report branching of adapted traits in drifting during the course of evolution. Individuals with high current velocity preferences either spend short (several seconds) or long (an hour) duration in water flow, while the individuals with low current-velocity preference only spend middle range (half an hour) of duration in water flow.

In order to achieve the optimized pest control, correct estimation of pest densities is a prerequisite to monitor pest damage and to provide efficient pest management plans. Parameters regarding diffusion (e.g., diffusion constant) and population size (e.g., growth rate) were estimated by using diffusion equation. The time series dispersal data of Whiteflies collected in greenhouse were used for modeling. Cross-correlation analysis was conducted to reveal the range and direction of pest population invasion. Sampling theory was further investigated regarding estimation of densities, and population dynamics of Whiteflies were discussed in two dimensions.