Nesting Biology and Relocation Dynamics in an Indian Ant Diacamma indicum

Kolay, Swetashree (2016) Nesting Biology and Relocation Dynamics in an Indian Ant Diacamma indicum. PhD thesis, Indian Institute of Science Education & Research Kolkata.

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Abstract

Eusociality is the most advanced form of social behaviour and is characterized by reproductive division of labour, cooperative brood care and overlap of two or more generations within the colony. The study species, Diacamma indicum, belongs to the subfamily Ponerinae in the family Formicidae and is widely found in the Indian subcontinent. The colonies occupy shallow subterranean nests each consisting of a single chamber connected to the exterior by a single tunnel. This thesis broadly explores the nesting behaviour and relocation dynamics of D. indicum. Including others, We also studied decision making and relocation dynamics when colonies encounter two alternate nesting sites in which a trade-off between nest quality and distance is present. Nesting biology of D. indicum across one year was studied in the field by observing more than 100 natural nests. Manipulative experiments were performed with 120 colonies in the field and 40 colonies in the laboratory to understand their response to different levels of flooding. The major findings of the thesis are as follows- The structure and location of D. indicum nests vary across the year with monsoon having the most profound effect; Tandem running is the only mode of relocation used by D. indicum colonies; Prior knowledge of the surroundings does not give the colonies any advantage while searching for and relocating to a new nest. Increased stress in the form of extended exposure of the colonies results in faster decision making and faster relocation; Colonies relocate to a nest which is of better quality than their current shelter whenever the opportunity arises and the relocation dynamics are unaffected by the degree of deterioration of the old nest; Consensus decision making during nest site selection is most likely not used with each scout deciding to initiate tandem running at an individual level after independent assessment of nest quality; and Only a subset of individuals who are capable of performing tandem runs become leaders during any given relocation and work distribution among these leaders is always right-skewed. The work done in this thesis has opened up several new avenues to explore. Further work has to be done on the nest architecture and monsoon biology of these ants. The factors which cause colonies to relocate, decision making during nest selection and the manner in which different stresses affect relocation dynamics have to be examined. Addressing these complex issues will help us understand not only the organization and execution of colony movement in D. indicum but also give us a broader insight into organization of work in insect societies.

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