Ant diversity in organic versus conventional rice paddies of Uttarakhand, India

Ants have emerged as a useful bioindicator taxon, yet ant communities have not been widely explored in agro-ecosystems where ants may serve important roles as bioturbators and predators of pests.  To investigate the impacts of farming on ant communities, we censused ants in rice paddies in which synthetic pesticides and herbicides were utilized versus “organic” rice paddies cultivated without the use of synthetic chemicals in Dehradun, Uttarakhand, India, at the end of the monsoon season, September, 2013.  For comparison, we collected data from disturbed habitats on the campus of the Wildlife Institute of India, Dehradun.   The 1,199 ant specimens collected from 59 pitfall traps yielded 22 ant species, with more than a two-fold difference in species richness between the Wildlife Institute Campus (17 species) and the farms (8 species).  Estimated species richness (Chao 1) differed between the farms with the organic having an estimated 11 +/- 3.9 s.d. species versus 6 +/- 0.87 s.d. species for the conventional.  Ant abundance was significantly greater (P<0.001) on the WII campus (59.95 ants per trap) compared to the farms (2.75 ants per trap in the rice paddies) and significantly greater (P<0.01) on the organic farm (4.93 ants per trap) compared to the conventional one (0.64 ants per trap).  The Shannon Index differed as well (WII Campus: 2.44 versus farms:1.44).  The striking differences in the ant communities demonstrate both the negative impacts of agricultural intensification on the ants of Uttarakhand, as well as the usefulness of ants as indicators of positive impacts of organic farming methods.