An insight into the quality of sacred groves – an island habitat – using leaf-litter ants as an indicator in a context of urbanization

Abstract

Sacred groves (SGs) of India are islets of forests providing ecosystem and spiritual services to man. Studies suggest that SGs are deteriorating on their quality due to urbanization, invasive species, land-use change, and religious modernization. We explored diversity, community, and abundance of overall and different functional groups of litter ants, including Anoplolepis gracilipes – an invasive ant – on paired SG-neighbouring home garden (HG) sites in rural and urban landscape to (a) assess the quality of SGs and (b) examine whether the variation in ant community of the two habitats was predicted by urbanization and abundance of A. gracilipes. We considered species and local contribution to β-diversity to identify species and sites crucial for conservation of sites. Abundance and richness of overall ants, proportional trap incidence of species, and abundance of A. gracilipes were similar on SG and HG, but species diversity and abundance of certain ant functional groups were higher on SG. Ant community of SG was different from HG, but was not affected by urbanization. A. gracilipes and rural SGs contributed the most to β diversity. A. gracilipes gave little pressure on native ant community. The study concludes that SGs, despite invaded by A. gracilipes, have potential for conserving biodiversity.

Urban tropical forest islets as hotspots of ants in general and invasive ants in particular

“…The sacred groves of the moderately-and less-urbanized sites were similar on the vegetation health. Our findings that the Yellow-Crazy Ant was hardly collected in the sacred groves of the less-urbanized sites agree to the patterns observed for the invasive ants along the disturbance gradients by previous studies elsewhere 17,30,31,51 .…”

“…Regardless of the locations, the sacred groves contain relics of evergreen forests of the size < 10 ha. While the floristic aspects of the biodiversity of the sacred groves of these States are well-known 36,37 , with our investigations, the faunistic aspects of the biodiversity of the sacred groves are just coming to the light 30,31,34,[38][39][40] . While the sacred groves of Kodagu are located on a land mosaic of human settlements, business districts, homeyards, coffee plantations, and protected forests, the sacred groves of Kasaragod and Trivandrum are located on a land matrix of human settlements, business districts, and Coconut-based orchards or homeyards.…”

“…Its trap incidence in the sacred groves of the moderately-urbanized site was increasing dramatically over the years 30 . It is suggested that the invasive ants, including the Yellow-Crazy Ant increase their population quickly in more disturbed environments than the less disturbed areas in the naturalized and invaded regions 17,30,31,51 . The sacred groves of the moderately-and less-urbanized sites were similar on the vegetation health.…”

“…gardens and parks that use no hazardous chemicals to manage insect pests or rodents are particularly rich and abundant on native ant species [21][22][23]26 . Sacred groves-the relics of biodiversity-rich natural forests [27][28][29] have a higher ant diversity 25,30,31 . Although a good number of studies are in agreement that urbanization can change the characteristics of ant communities [16][17][18][19][20][21][22] and favour invasive ant species in urban green spaces 15,30,32,33 , Nooten et al 26 found that the sacred groves of urban Hong Kong encompass a higher richness of native and specialist ants, which are resilient to invasive species.…”

“…and (3) whether the native ant communities of the sacred groves were resilient to the invasion by the Yellow-Crazy Ants? In the entire study, we gave a special status for the Yellow-Crazy Ant because it is one of the 100 globally notorious invasive species 35 and a rapidly range expanding plausible native species of south India 30,31,34 .…”