Understanding the patterns of how biodiversity is distributed has been a central question in ecology. Need to understand this has gained priority in recent times due to an accelerated human induced land-use change leading to global declines in biodiversity. To understand these patterns of biodiversity distribution, beta-diversity is becoming a widely used concept since it has the ability to be more interpretive than alpha diversity, is better suited to test general ecological models and provides good insights for conservation and management practices.
In this study, we ask how taxonomic species, functional groups and land-use contribute to beta diversity, partitions of beta diversity and whether invasive species have a disproportionate influence on beta diversity. We answer these questions using ants in Goa, India since they are one of the most diverse, abundant and ecologically significant organisms on earth, and contribute significantly to various ecological functions. Species Contribution and Local Contribution to Beta diversity were calculated using the beta.div function within the “adespatial” R package, while beta diversity was partitioned into replacement and nestedness using beta.div.comp function. Generalised dissimilarity modelling was used to understand dissimilarity of ant communities at regional scale using gdm package . “FD” package was used to group species into functional groups using a trait dataset to evaluate a dendrogram and create functional groups based on trait similarities.
Results/Conclusions
We record 68 species of ants of which five are invasive and classified the recorded species within six functional groups from 277 sites distributed within five land-use types. At the taxonomic species level, Oecophylla smaragdina a common arboreal species of the tropics and the globally important invasive Anoplolepis gracilepis contributed the most to beta-diversity. At the functional group level, the group comprising of large-bodied decomposers, contribute the most to beta-diversity. Lateritic plateaus and forests contributed most to beta-diversity whereas this contribution drastically decreases in human influenced land-uses. At taxonomic species level, beta diversity of ant communities is explained more by species replacement between sites however at functional group level there is more nestedness within sites. We found that sites with no invasive species contributed more to beta diversity than sites which had invasive species and this effect progressively strengthens with an increase in the number of invasive species at a site.
Our results suggest a strong relationship between human influence on land-uses resulting in the reduction of beta diversity and a disproportionate influence of invasive species in this landscape.