Effects of Over-Harvesting and Drought on a Predator-Prey System with Optimal Control

In this paper, a two species predator-prey model is developed where prey is affected by over-harvesting and drought and predator is affected by drought. The intention is to investigate the impact of over-harvesting and drought on predator-prey system, and suggest control strategies to alleviate the problem of loss of prey and predator species due to over-harvesting and drought. The control strategies suggested are creation of reserve areas with restriction of harvesting for controlling over-harvesting and construction of dams for mitigating drought effects. The results obtained from theoretical and numerical simulation of the predator-prey model with harvesting and drought without control strategies showed that, both harvesting and drought affect the predator-prey population negatively. However, the results obtained from numerical simulations of the model with control measures showed that, the use of control strategies one at a time encourages the increase of the prey and predator species to the optimal population size. Furthermore, the best result is obtained when control strategies, creation of reserve areas with restriction of harvesting and construction of dams are applied simultaneously.

Floral resources, pollinators and fruiting in a threatened tropical deciduous tree

Nothapodytes nimmoniana(Family Icacinaceae)is a deciduous tree species distributed in Asia facing severe population decline.Wood chips from the tree are a source of camptothecin,a globally soughtafter alkaloid with cancer-treating properties,and are harvested unsustainably in natural forests.We studied the pollination ecology of the species and asked if there are constraints in pollination and fruiting success in its natural populations.We also discuss the potential effects of wood extraction on pollinators and reproductive success in the population.Methods The study was carried out during the flowering season in two populations with varying exploitation levels,both located in the Protected Area Network in the Western Ghats of Karnataka State.We assessed floral resource availability and measured pollinator diversity and activity in the canopy from the perspective of the biology of the species.We quantified pollinator abundance and percent fruit set as a function of population density.Important Findings Flowers belong to the fly pollination syndrome and are open to visits by generalists such as Apis dorsata and Trigona iridipennis.Fruiting success did not vary between exploited and unexploited sites,but there was a significant difference in pollinator assemblage.In a lean male flowering year,fruit set was low,suggesting pollen limitation in the population.No fruiting was recorded in the second year at the site where trees were felled soon after the flowering period.We argue that when male floral resources are altered in exploited populations,pollinators of generalist nature may show a shift in foraging pattern.Also,generalist plants may be as susceptible to pollination loss as are specialist plants.The need for outcrossing in the species would probably exacerbate this vulnerability.