Anonychomyrma inclinata

Anonychomyrma inclinata is an arboreal nesting species, almost always found in trees carrying mistletoes. They are often associated with Hypochrysops piceatus and other butterflies.

Identification
Based on workers, A. inclinata can be differentiated from most Australian species by its low, sloping propodeum, which has moderately prominent spiracles and an obtuse angle between the dorsal and declivitous faces, combined with the moderate hairiness of the body. Anonychomyrma itinerans (including all subspecies), Anonychomyrma fornicata, Anonychomyrma malandana and Anonychomyrma nitidiceps have strongly rounded, domed or protuberant propodea with the dorsal surface relatively short. The more similar Anonychomyrma gilberti is readily recognised by its longer legs, scapes exceeding the posterior margin of the head by at least their maximum diameter, abundant hairiness and dense downy yellow pubescence, giving a shaggy appearance. Anonychomyrma biconvexa Santschi, 1928 has shorter scapes that do not reach the posterior margin of the head; the occipital border is more deeply concave; and the propodeum is evenly rounded, not planar, and less hairy.

From those species for which only queens are described and images are available, A. inclinata can be differentiated on the basis of head morphology. Anonychomyrma longiceps is readily differentiated by its extremely elongate head. The sides of the head of Anonychomyrma froggatti are straight and very nearly parallel, the eyes smaller, scapes shorter, the centre of the clypeus projects further and the posterior ocelli are more closely set than A. inclinata. In Anonychomyrma arcadia, the eyes are smaller and the scapes clearly exceed the upper margin of the posterior ocelli. In addition, the rear margin of the head of A. inclinata curves sinuously before reaching the centre of the concavity, a feature not present in any of the other three species.

For two other Australian species, no extant specimens or images exist, and the descriptions are brief. The workers of Anonychomyrma purpurescens are described as having purplish iridescence and nesting in the ground (Lowne 1865), neither of which are characteristic of A. inclinata. Anonychomyrma procidua is based on a queen collected in Tasmania (Erichson 1842) and is described as a black ant with a nearly square head.

Although morphology and distribution made A. inclinata unlikely to be among the undescribed Wet Tropics species identified in Leahy et al. (2020), this was confirmed by generating standard cytochrome c oxidase subunit 1 (COI) barcode data for two individuals of A. inclinata for comparison with those of the undescribed Wet Tropics species. Both sequences were identical, and no match was found with the Leahy et al. (2020) species, A. inclinata having a COI sequence 11.9% divergent from the most similar Wet Tropics species. The COI data for the specimens (ANIC 32-146120) are available on GenBank (accession number MZ313336).

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Nesting and foraging behaviour
Anonychomyrma inclinata is arboreal, making its colonies almost exclusively in mature live trees with access to internal hollows through fissures and cracks, lightning scars or broken limbs. Rarely nests are found in fallen trees. No colonies have been observed in the ground or under logs. The ant will occupy any of the tree species noted above if they are old enough to have suitable nest sites (Sands 2018a, 2019), and at the sites examined in northern New South Wales and southern Queensland, almost all trees populated with A. inclinata carried mistletoes. Anonychomyrma inclinata has been observed harvesting nectar from flowering mistletoes, particularly Lysiana exocarpi subsp. tenuis and Amyema linophylla subsp. orientalis, as well as nectar from flowering eucalypts, shrubs including Jacksonia scoparia and Kunzea opposita, and the epiphytic orchid Cymbidium canaliculatum. Honeydew from psyllids and scale insects also appears to be an important part of the ant’s diet (Sands 2018a) along with insect prey gleaned from trees and the ground surface.

As well as providing suitable nest cavities and ready access to nectar and honeydew, large live trees probably offer the colonies greater protection from fire and extremes of heat and cold compared with dead or fallen timber due to their greater thermal buffering capacity (Shelton et al. 2020). The ants are active throughout the year, but foraging is strongly reduced once the temperature reaches 30–35 °C and only resumes once the temperature declines (D. Sands unpubl. data). The ants forage in the nest tree and adjacent trees, and on the surrounding ground. Strong trails have been observed up to 20–25 m between trees and up into the canopy, and the ants preferentially use fallen logs and branches to move across the ground between trees.

Colony structure
A queen and male specimens were collected from a nest in a recently fallen silver-leaved ironbark, Eucalyptus melanophloia subsp. melanophloia, approximately 15 m tall, with diameter at breast height of 25 cm. The tree was sectioned into 30 cm lengths and examined for queens, alates, workers and brood by vigorously shaking and hammering each section to dislodge ants from the nest into containers. For each section, a subsample of workers and males was counted, and then the number of remaining ants was estimated proportionately. Brood from each section were subsampled and later counted in the laboratory. The colony occupied abandoned termite tunnels accessed via a damaged area of the trunk approximately 10 m above ground. An estimated 13 000 workers were present in this nest, along with a single queen, no female alates, approximately 40 male alates and 160 000 brood at various stages, a total population in excess of 170 000. It was not possible to estimate the number of workers foraging outside the nest, but long, active trails were present. The total length of trunk and branches occupied by the colony was approximately 10 m and had a volume estimated at 12.5 L. The queen and bulk of the adults and brood were in the lower section of the nest, immediately above the nest entrance. Termite tunnels extended below the nest entrance but were partially water filled, which precluded their use for nesting but afforded the colony ready access to moisture. Several silverfish were also present in the nest, probably an undescribed species of Acrotelsella Silvestri, 1935. This genus of silverfish has been found previously in abandoned termite galleries in Australia but not in an active ant nest before (G. Smith pers. comm.).

Interaction with Hypochrysops piceatus and other butterflies
Freshly eclosed H. piceatus larvae have been observed being carried by the ant to protection in hollows and shelters and at dusk are carried or guided by the ants to the soft terminal leaves of the bulloak to feed (D. Sands, unpubl. data). Overwintering H. piceatus larvae shelter in hollows or under bark and pupae are found in similar locations, always attended by A. inclinata. At the Leyburn site, A. inclinata has also been observed attending immatures of other lycaenid butterflies, including those of Hypochrysops cyane Waterhouse & Lyell, 1914 and Ogyris amaryllis meridionalis Bethune-Baker, 1905 (Sands 2019).

Nomenclature

 * . Anonychomyrma inclinata Lewis & Sands, 2021: 465 (w.q.m.) AUSTRALIA (Queensland).

Type Material



 * Paratypes
 * Queensland: ☿1 ‘28°19′S 150°30′E. Bendidee Nat. Pk. Site 5. 21–22 Mar 2003. 51144. J. Haines. 235 m. Brigalow wilga. Mushroom trap’ (QM). ☿1 ‘24.840°S 147.781°E. 8–14 Oct 2014. Carnarvon Stn Conglomerate Spring. Eucalyptus crebra woodland. 865 m. Pitfall. S. Wright, N. Starick. 37076’ (QM T231707 (QM)). ☿3 ‘Ellangowan Nat. Ref. Leyburn. 27.957693°S 151.659129°E. 1 Sep 2019. Casuarina woodland. Trail on Eucalyptus tereticornis. J. Lewis & D. Sands Coll #764’ (ANIC 32-146127 (ANIC, MCZ)). ☿1 ‘NE Goondiwindi. 28.308386°S 150.461702°E. 4–6 Nov 2020. Roadside. On Bulloak. Sands, D. WC1’ (ANIC 32-158094 (ANIC)).
 * New South Wales: ☿1 ‘Dthinna Dthinnawan NP. 28.74203°S 150.86459°E. 1 Nov 2018. On bulloak with scar. Sands, D & Andren, M’ (ANIC 32-146122 (AM)). ☿1 ‘Nth Yetman. 28.74920°S 150.78232°E. 30 Apr 2019. On bulloak and Angophora. Sands, D. RT7’ (ANIC 32-146120 (NHM)). ☿1 ‘Nth Yetman. 28.74935°S 150.7820°E. 30 Apr 2019. On E. crebra 5 m from bulloak. Sands, D. RT5’ (ANIC 32-146124 (ANIC)). ☿1 ‘Dthinna Dthinnawan Nat. Res. 28.770837°S 150.74524°E. 2 Sep 2019. Casuarina forest. Nest in Allocasuarina luehmannii. J. Lewis Coll #772’ (ANIC 32-146133 (ANIC)). ♀1 ♂3 ☿3 ‘North Star Rd, SW Yetman. 28.946984°S 150.729708°E. 5 Feb 2021. J. Lewis Coll #824. Ant nest in termite tunnels in Eucalyptus 10 m above ground. Mixed woodland Eucalypt, Allocasuarina, Cypress’ (♀1 ANIC 32-158095 (ANIC); ♂3 ANIC 32-159096, 32-159097, 32-159098 (ANIC); ☿3 ANIC 32-158103, 32-158104, 32-158105 (ANIC)).