Distribution of the ant (Hymenoptera: Formicidae) fauna in the canopy of the mangrove tree Sonneratia alba J. Smith in northern Australia

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Abstract
The distribution and density of the ant fauna in the canopy of the mangrove tree Sonneratia alba J. Smith were investigated in Darwin Harbour, Australia. Ten ant species were found on Sonneratia but on the experimental trees only Camponotus sp. A, Crematogaster sp. A, Tetraponera punctulata Smith and Tapinoma spp. occurred at high densities. Camponotus sp. A was by far the most common species and is only known from Sonneratia. Samples of Sonneratia branches were taken at 1‐m intervals from 4 to 10 m above the lowest astronomical tide (LAT) level. A total of 278 nest chambers was dissected from the branches and the contents identified and counted. All observed nests were inferred to have been excavated by Camponotus sp. A queens, which were often observed excavating small cavities in the green shoots. The nest chambers were all small (5.2 ± 0.6 cm), normally covering only one internode, and the mean number of workers of Camponotus sp. A per nest was only 15.9. Chambers have only one small entrance, which can be blocked by a major worker or the queen with their head during high tide. The percentage of twigs hollowed out and inhabited by ants ranged from 2% at 4–5 m to more than 25% higher than 9 m above LAT. Queens were never observed in internodes that were more than 1 year old, although workers and brood were present. It is therefore assumed that the queens die shortly after colony founding and that the workers take over reproduction through some sort of thelytokous parthenogenesis.