Michel-Olivier Laurent, PhD

Currently I am a JSPS postdoctoral fellow in the faculty of agriculture, University of the Ryukyus, in the laboratory of Professor Kazuki Tsuji. Here, I will study the relocation dynamics Diacamma ants. More precisely a species found in Okinawa: Diacamma sp. from Japan.

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Diacamma belongs to the subfamily ponerinae and is distributed in Asia and Oceania, from eastern India to Japan, and from southern China to northeast Australia. They form colonies of medium to small size (around 100 workers), and readily relocate nest site after disturbances. Diacamma are queenless and only mated workers (gamergates) reproduce. Diacamma ants have a small appendage in the thorax called gemmae. This appendages are mutilated by the gamergates from any worker that ecloses after the them. These appendages play a role in the reproductive capabilities of workers, because once mutilated, ants are incapable of mating.

The genus Diacamma uses tandem running when foraging for food and when relocating to a new nest. A forager, once it has found a food source or nest site, will lead single worker towards that location. In Diacamma, around 24% of the colony’s workers go outside the nest for foraging and other activities while the gamergates only leave the nest to relocate to the new nest. During a relocation event, the foragers act as leaders, and, as found in other species, among those leader there is generally a single individual that is more active in the relocation (initiates more tandem runs), and when this individual is removed the relocation dynamics is significantly altered. However, any leader lost, including the principal tandem leader, are eventually replaced. Indeed, these substitutes are able to complete the relocation successfully at a similar rate.

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In this project, I will study this relocation behavior of Diacamma after a disturbance of their nest. In particular I will focus on the role of foragers, distance of new nests, and local food availability in the relocation dynamics. In addition, I will observe if Diacamma ants relocate to previously occupied nests, even if foragers have most recently only been able to visit other nest sites. These observations will help me elucidate if colony-level memory out-weights the forager’s recent memory. Another important factor that surely affects the new nest choices is the presence of competitors.  Indeed, it has been shown that Diacamma ants are very hostile towards non-nestmates, regardless of the distance between nests. This hostility can be seen on the location of different Diacamma colonies in the field, where they are distributed homogenously, with each colony avoiding each other. In this project, I will see how the relocation of a Diacamma colony is affected when a previously used nest has been recently occupied by another Diacamma colony.

 

Lastly, I will carry out field experiments where I will study the position and size of Diacamma colonies and how they are distributed compared to the position of other ant colonies (heterospecific or conspecific). In particular I am interested in elucidating which interaction, intraspecific or interspecific, more strongly affects demography of Diacamma foragers. It is believed that ants are more aggressive to conspecific individuals from different colonies than heterospecific individuals.  However, the consequence of this different levels of aggression depending on the ant species involved on the ant demography is empirically unknown. The determination of the strength of inter- and intra-specific competition is fundamental in community ecology. It is my hypothesis that ants are more aggressive to conspecific individuals than heterospecific individuals, and, consequently, foragers of Diacamma will be subjected to higher mortality levels when their nest is surrounded by other Diacamma nests than when surrounded by other ant species.