SUMMARY

Insects form a major part of the animal biomass in the ecosystem and in recent times they have been used as indicator species. Ants represent a unique focal group, to be monitored, due to their ability to navigate across all trophic levels, along with their sensitivity to any changes in the environment. Endemism in ant species suggest that their occurrence and their absence could be due to certain specific reasons. In the Indian scenario, Lasius species of ants are present only at the base of Himalayas, Harpegnathos saltator only in the southern India, while H.venator occupies the northern regions of India. Species of Strumigenys are present in forests prominent of thick leaf litter, while Tapinoma melanocephalum is present in human interfered systems. This definitely shows in a small way, that ant fauna does vary geographically, across latitudes. To understand the diversity and the stability of an ecosystem, hence, it becomes important to study the species composition changes that occur due to variations in microclimate and habitat.  This would help in biodiversity conservation endeavor as it aids in inventorying and mapping of biodiversity and also in demarcating the most seriously threatened ecosystems. With global remote sensing land cover data sets being nowadays increasingly available at high temporal resolutions, it becomes imperative to combine with it field surveys to provide powerful tools for biological resource assessments.

The study carried out at the Sharavathi river basin, Shimoga, Western Ghats, aims to determine the species composition and assemblages of ant fauna, across the varying landscape elements. GIS and Remote sensing have been used to derive information about the land cover and land use patterns, which are the niches for ants. This study has revealed that ant species composition varies drastically across vegetation types. Dominance of certain species increases while others decrease, with variation in habitat. Species that have highly specific requirements remain absent from disturbed habitats. This work has resulted in identifying certain biological indicators such as Polyrhachis mayri and Oecophylla smaragdina as species thriving in undisturbed evergreen- semievergreen forests and moist deciduous forests respectively, while Anoplolepis longipes has been identified as an invasive species. This study reveals the tremendous human pressure exerted towards the northern and eastern region of the river basin while contiguous forests were present only towards the western region (devoid of invasive species) of the study area.