Seasonal polyphenism of selected satyrid butterflies in some forest ecosystems of Bangladesh

Abstract

Butterfly is the best biotic indicator for assessing climatic changes and sustenance of forest healthiness. It is related with all the layers of vegetation (canopy, man-height and soil surface forest) in a forest ecosystem. Butterfly ' s presence in an ecosystem is the biotic vital safeguard for all trophic levels. It means that quantitative presence of the butterflies indicates the status of them in maintaining sound population equilibrium for the plants and the animals in an ecosystem. The butterflies are very sensitive to climatic changes, habitat changes and also to impacts on biodiversity in an ecosystem. For assessing healthiness of a forest ecosystem, the butterflies are use as a biotic indicator. Considering the importance of butterflies an attempt was under taken to study on "Seasonal polyphenism of selected satyrid butterflies in some forest ecosystems of Bangladesh" from November 2013 to October 2016. The research work was carried out in the forest of Bhawal National Park, Gazipur, Madhupur, Tangail and Satchori National Park, Habiganj. A few experiments were also conducted in Zoological Garden, Curzon Hall, University of Dhaka. Identification of satyrid butterflies is a prime importance to understand ' biotic and abiotic interactions' as tools for wildlife conservation and conservation of nature . Satyrid butterflies were collected from different forest areas and examined them in the Environmental Biology and Biodiversity Laboratory (EBBL), Department of Zoology, University of Dhaka to identify. During the research period, 38 species of satyrid butterflies under six genera were identified and specimens were preserved to future reference. Diversity, seasonal abundance and monthly fluctuation and their status were observed and recorded in the field condition. Relations between the butterflies and the abiotic­ biotic factors were emphasized on the butterfly abundance in the target forest ecosystem throughout the entire study period. Biology of three selected satyrid butterflies was examined under optimum temperature and relative humidity in the EBBL. The phenology of their host plants and butterfly-host plant interaction, and different seasonal forms (dry and wet season forms) were also observed during the study period. The seasonal polyphenism at adult stage of three selected satyrid butterflies were examined considering the presence of abiotic factors. The different behavioural aspects viz. adult emergence, feeding (foraging, fruit juice intake and tree sap intake), puddling, basking, mating and egg-laying behaviour of satyrid butterflies and their related plants were observed and recorded both in field and laboratory conditions. These biotic indicators could ensure the detennining tools to measure climatic change effects on ecosystem, biodiversity, wildlife and on nature as a whole . It is believe that the monitoring system based on biotic indicator-techniques will also ensure to forecasting system and will ultimately help in shaping development of adaptation strategies to be taken against the climate change impacts.