Tropical habitats face a number of threats as a result of human activities. Two common and important anthropogenic threats to tropical biodiversity are invasive species and roads. Roads can have negative ecological consequences by degrading and fragmenting habitat, causing edge-effects, and increasing the risk of road-related mortality, hunting, fire and spread of invasive species. Lantana camara (henceforth lantana), a widespread invasive plant, can form dense monoculture thickets covering large areas, and yet knowledge is rare about its impacts on higher trophic levels, especially insects. I studied impacts of these two important proximate drivers of habitat disturbance, namely lantana and roads, on habitat use by butterflies in a tropical moist deciduous forest in Western Ghats of India. Both are expected to modify micro-habitat structure, resources, micro-climate and other aspects of the ecology of butterflies and thereby influence how they use space (i.e., micro-habitats within the larger habitat). Because systematic ecological information on tropical butterflies is comparatively limited, I adopted a multi-species approach. I examined habitat use responses of butterflies to a gradient in lantana cover within the forest, and to an unpaved road passing through the forest. The abundance of a butterfly species in different micro-habitats was taken as a measure of its habitat use. Data was collected over two seasons and at two spatial scales. Road and lantana were found to influence habitat use by butterflies. While there was substantial difference in the kinds of butterflies encountered on the road vs. the forest interior, high lantana areas in the interior appeared to contain only a subset of species encountered in low lantana areas. At a smaller spatial scale, a different set of species was encountered on lantana plots as compared to non-lantana plots. I then correlated the responses of butterfly species to road and lantana with their functional traits, as a way to detect general patterns. For this, I built a traits’ database by measuring morphological traits in 254 butterfly species from India and classifying them according to their habitat preferences (based on expert opinion). I examined relationships between morphological traits, habitat preference and evolutionary relatedness in butterflies. I then examined patterns of correlation between these traits and responses to the two habitat disturbances and found that certain traits can help predict response.
To summarize, my study suggests that butterfly habitat use is influenced by forest disturbance due to roads and lantana, though the response varies across species. Species with
certain traits may be especially vulnerable to these disturbances. The behavioural habitat use responses observed in my study can have population or community-level consequences that need to be further examined.