Thesis Colloquium at CES on 13 June 2019 at 11:00 am titled "Multimodal duetting and pair formation in a paleotropical false leaf katydid (Onomarchus uninotatus)" by Aswathy N. Nair from IISc
Resource distribution and parental investment can influence pair formation strategies by affecting spatiotemporal distribution of potential mates. Animals can distribute in response to resource availability and parental investment can alter the ratio of receptive sexes in the population at any given point in time.
Onomarchus uninotatus, a Pseudophylline katydid species, exhibits a unique multimodal duetting system among katydids. Males broadcast long range acoustic signals and the females respond via vibratory signals which are then used by males to localise the females. Laboratory experiments have established vibratory signals to be an immediate response to male calls even at the threshold of female hearing.Being a canopy species, relying on short range vibratory signals for localisation across trees and at larger distances within a tree seems paradoxical. In my thesis,I investigated the localisation strategies in O. uninotatus across these two spatial scales, i.e. within tree and between trees and aimed to understand if roles played by the sexes are reflected in their relative parental investment.
For the across-tree scale, acoustic environment of calling males and females in their natural habitat was studied alongwith the distribution of their host plants (Artocarpus spp.).Both females and calling males were found to be able to hear calls of males from neighbouring trees. Flight experiments to investigate female response to male calls suggest that females may perform flight phonotaxis to locate calling males across trees. A simulation framework was then used to study the optimal mate encounter strategies that males and females can employ at the across-tree spatial scale. At the within-tree spatial scale, interactions between a calling male and a responsive female at two different distances on a branch were investigated.Results suggest that irrespective of their distance from the caller, females always tremulate first and can contribute to localisation via phonotaxis at larger distances. Finally, I examined the parental investment of the sexes by quantifying their resignaling intervals.Preliminary results indicate that both the sexes have comparable parental investments.
We conclude that in O. uninotatus, at distances where female tremulation signals can be perceived, males bear the onus of search. At larger distances where, female tremulation signals cannot be perceived, females can also contribute to localisation. Therefore, both males and females contribute to signalling and matesearch, which is reflected in their relative parental investments.