Impact of Extrinsic Chemicals on the Behavioural Ecology of an Indian Ant Diacamma indicum

Acharjee, Anwesha (2026) Impact of Extrinsic Chemicals on the Behavioural Ecology of an Indian Ant Diacamma indicum. PhD thesis, Indian Institute of Science Education and Research Kolkata.

Text (PhD thesis of Anwesha Acharjee (18RS054)) 18RS054.pdf - Submitted Version Restricted to Repository staff only Download (10MB)

Abstract

Insects comprising over half of all living organisms are experiencing a global decline, leading to major imbalances to the ecosystem. Anthropogenic stressors like chemical pesticides, are one of the major factors causing behavioural and physiological changes and driving this decline. Ants constitute two-thirds of the biomass of all insects, but very few studies have investigated the impact of pesticide on non-target ants. Using Diacamma indicum, a tropical ponerine ant as a model system, we investigated the impact of a pesticide- cypermethrin (a neurotoxin), and a herbicide- glyphosate. Simulating field-relevant contamination, we tested the impact of these extrinsic chemicals on major axes of their lives like colony living, reproduction, memory, learning, colony residence time, and ability to relocate. Lab and field-based experiments were performed using more than 200 ant colonies and analysed using statistical models to understand the impact at the level of the individual and the colony. Additionally, a survey was conducted to understand the pesticide use patterns by local farmers. Even at one-fourth of the recommended dose in lab condition, cypermethrin induced negative behavioural effects in the ants. Colony living and reproductive status was not significantly impacted by cypermethrin and glyphosate. Tandem leaders and foragers who were exposed to cypermethrin were significantly impaired in their ability to navigate back to their nest. Nest relocation together with nest choice was significantly negatively impacted. No effect of glyphosate exposure was found on tactile associative learning but glyphosate contamination near natural ant nests resulted in higher probability of nest relocations compared to cypermethrin and control colonies. In conclusion, this study reveals the negative effects of sub-lethal dose of pesticide and herbicide on the behavioural ecology of a non-target ant species indicating the possibility of major ecosystem disruption.

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