Interrelations between the Harvester Ant Veromessor Pergandei (Mayr) and Some Desert Ephemerals

Lloyd Tevis

doi:10.2307/1931610

Pheromone cue triggers switch between vectors in the desert harvest ant, Veromessor pergandei

10.31219/osf.io/2x5qr ◽

2020 ◽

Author(s):

Cody A Freas ◽

Marcia L Spetch ◽

Jenna Congdon

Keyword(s):

Path Integration ◽

Trail Pheromone ◽

Column Vector ◽

Vector System ◽

Distance Estimate ◽

Harvester Ant ◽

Veromessor Pergandei ◽

Spatial Locations ◽

Potential Use

The desert harvester ant (Veromessor pergandei) employs a mixture of social and individual navigational strategies at separate stages of their foraging trip. Individuals leave the nest along a pheromone-based column, travelling 3-40m before spreading out to forage individually in a fan. Foragers use path integration while in this fan, accumulating a direction and distance estimate (vector) to return to the end of the column (column head), yet foragers’ potential use of path integration in the pheromone-based column is less understood. Here we show foragers rely on path integration both in the foraging fan as well as while in the column to return to the nest, using separate vectors depending on their current foraging stage in the fan or column. Returning foragers displaced while in the fan oriented and travelled to the column head location while those displaced after reaching the column travel in the nest direction, signifying the maintenance of a two-vector system with separate fan and column vectors directing a forager to two separate spatial locations. Interestingly, the trail pheromone and not the surrounding terrestrial cues mediate use of these distinct vectors, as fan foragers briefly exposed to the pheromone cues of the column in isolation altered their paths to a combination of the fan and column vectors. The pheromone cue acts as a contextual cue triggering both the retrieval of the column vector memory and its integration with the forager’s current fan vector.

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The non-additive effects of body size on nest architecture in a polymorphic ant

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2017.0235 ◽

2018 ◽

Vol 373 (1753) ◽

pp. 20170235 ◽

Cited By ~ 5

Author(s):

Christina L. Kwapich ◽

Gabriele Valentini ◽

Bert Hölldobler

Keyword(s):

Body Size ◽

Synergistic Effects ◽

Mating Frequency ◽

Nest Architecture ◽

Harvester Ant ◽

Insect Societies ◽

Interdisciplinary Approaches ◽

Size Groups ◽

Veromessor Pergandei ◽

Colony Level

Like traditional organisms, eusocial insect societies express traits that are the target of natural selection. Variation at the colony level emerges from the combined attributes of thousands of workers and may yield characteristics not predicted from individual phenotypes. By manipulating the ratios of worker types, the basis of complex, colony-level traits can be reduced to the additive and non-additive interactions of their component parts. In this study, we investigated the independent and synergistic effects of body size on nest architecture in a seasonally polymorphic harvester ant, Veromessor pergandei . Using network analysis, we compared wax casts of nests, and found that mixed-size groups built longer nests, excavated more sand and produced greater architectural complexity than single-sized worker groups. The nests built by polymorphic groups were not only larger in absolute terms, but larger than expected based on the combined contributions of both size classes in isolation. In effect, the interactions of different worker types yielded a colony-level trait that was not predicted from the sum of its parts. In nature, V. pergandei colonies with fewer fathers produce smaller workers each summer, and produce more workers annually. Because body size is linked to multiple colony-level traits, our findings demonstrate how selection acting on one characteristic, like mating frequency, could also shape unrelated characteristics, like nest architecture. This article is part of the theme issue ‘Interdisciplinary approaches for uncovering the impacts of architecture on collective behaviour'.

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