Microhabitat variation of ant nests mediates the local distribution and abundance of an ant associate

Abstract

Symbionts form intricate associations with their hosts. They can only establish when potential hosts are present, but their distribution is in addition often influenced by microhabitat preferences, which may not overlap to those of their hosts. This leads to a local patchy distribution of the symbiont, where it is present with some hosts while being absent from others. We studied the drivers of local distribution and density of Cyphoderus albinus, an obligate ant-associated springtail, across a mosaic of ant nests. The ant hosts display intra- and interspecific variation in nest structures, including soil, dead wood, arboreal and thatch mound nests. The springtail was always present in the thatch nests of red wood ants (Formica rufa group) and the arboreal nests of Lasius fuliginosus. A high prevalence was recorded in the smaller thatch mounds of Formica sanguinea. There was a higher likelihood to find the springtail in dead wood nests of Formica fusca, Lasius and Myrmica species compared to the soil nests of these host taxa. The springtail densities in thatch nests of Formica (F. rufa group and F. sanguinea) were much higher than those in other nest types and reached the highest densities (1148 individuals per L nest material) recorded for a social insect symbiont. Our findings emphasize that host nests with wood structures and thatch material provide a more favourable habitat for this symbiotic springtail compared to soil nests. Overall, this study underscores the importance of microhabitat variation in the local distribution and density of a symbiotic species.