DOI: 10.13102/sociobiology.v64i3.1030Sociobiology 64(3): 366-368 (September, 2017) Open access journal: http://periodicos.uefs.br/ojs/index.php/sociobiology ISSN: 0361-6525 The Plesiobiontic Association of Formica lemani Bondroit with Lasius flavus (Fabricius) (Hymenoptera, Formicidae) in Norway Introduction Interspecific nesting associations in ants are common, and can take several different forms including brood parasitism, cleptoparasitism and mutualism. However, in many compound nests the association appears to be fully commensal, as different species may occur together in the same nest without interacting biologically. Such associations are typically called plesiobiontic or plesiobiotic relationships (See Kanizsai et al., 2013 for a review). Plesiobiontic ant species pairs tend to be dissimilar in e.g. size, morphology and behaviour (Kanizsai et al., 2013), and Czechowski (2004) suggested that plesiobioses primarily form in landscapes where suitable nesting habitats are scarce. In their review of plesiobiosis in Holarctic ants, Kanizsai et al. (2013) noted that the ants most frequently involved Abstract Three compound nests of Formica lemani Bondroit, 1917 and Lasius flavus (Fabricius, 1782) are reported from Lygra, Western Norway. This is the first plesiobiontic relationship reported for F. lemani and the 9th for L. flavus. Behavioural and landscape ecological traits associated with plesiobiosis are discussed. Sociobiology An international journal on social insects GM Kvifte1, TA Legøy2, J Soulé2 Article History Edited by Evandro N. Silva, UEFS, Brazil Rodrigo Feitosa, UFPR, Brazil Received 23 March 2016 Initial acceptance 09 May 2016 Final acceptance 01 May 2017 Publication date 17 October 2017 Keywords Plesiobiosis, interactions, mixtobiosis, commensalism, mixed colonies. Corresponding author Gunnar Mikalsen Kvifte Dept. of Natural History, University of Bergen University Museum of Bergen P.O. Box 7800 N-5040 Bergen, Norway E-Mail: gunnar.kvifte@uib.no in plesiobiontic relationships tend to be comparatively less aggressive ants, and that plesiobiont partners tend to show little overlap in foraging strategies. The most frequently plesiobiont species in the Holarctic region is Formica fusca L., 1758; which forms part of more than 60% of observed plesiobiontic relationships (Kanizsai et al., 2013). Despite the two species Formica lemani Bondroit, 1917 and F. gagatoides Ruzsky, 1904 being overall very similar to F. fusca in behaviour and biology (Collingwood, 1979), no plesiobiontic associations of either species were listed by Kanizsai et al. (2013). In this note we document the first record of plesiobiosis in the ant species Formica lemani, from a nest shared with Lasius flavus (Fabricius, 1782) in a heathland ecosystem in Norway. The observations contribute the 50th observed plesiobiont species and the 49th observed species association pair in Holarctic ants. 1 - Department of Natural History, University Museum of Bergen, University of Bergen, Norway 2 - Institute of Biology, University of Bergen, Norway SHORT NOTE Sociobiology 64(3): 366-368 (September, 2017) 367 Material and methods Ant nests were searched for under rocks and roots and in bryophytes on august 18th and 26th, 2015, at Lyngheisenteret, Lygra, Western Norway. The area is part of an open heathland landscape which is grazed by sheep through the year and managed by controlled burnings approximately once a decade. A total of nine people were involved in the search, which spanned around 100 m2 of area surrounding 60.700736° N, 5.100393° E. Three different compound nests and one single-species nest were found, all under rocks, and voucher specimens of pupae and workers from each compound nest were collected for subsequent identification. Specimens were identified using Douwes et al. (2012). Adult and pupal voucher specimens from two nests are stored in alcohol in the entomological collections at the University Museum of Bergen (ZMUB, collection numbers A-47723–A-47728, see table 1 for details). Fig 1. Detail of ant nest after removal of stone. A, Lasius flavus pupae, B, Lasius flavus worker, C, Formica lemani worker, D, Formica lemani pupae. Museum ID Nest # Species Number of specimens Collection date A-47723 1 Lasius flavus 2 workers, 5 pupae 18.VIII.2015 A-47724 1 Formica lemani 7 workers 18.VIII.2015 A-47725 2 Lasius flavus 3 workers, 3 pupae 18.VIII.2015 A-47726 2 Formica lemani 1 worker, 1 pupa 18.VIII.2015 A-47727 2 Lasius flavus 6 alates, 5 workers, 1 pupa 26.VIII.2015 A-47728 2 Formica lemani 1 worker, 1 pupa 26.VIII.2015 Table 1. Voucher material preserved in this study. Results and Discussion All three compound nests were found under rocks and contained workers and pupae of both Lasius flavus and Formica lemani. In one of the nests, six alate L. flavus were collected as well. In each nest, pupae of the different species were found in different clusters, separated by a few centimeters (Fig 1). When the nests were uncovered, worker ants evacuated the pupae via apparently different systems of soil corridors. Apart from this small separation, no difference in microhabitat use could be observed. Adult workers could be observed among pupal clusters of different species, however this may be due to our disturbance of the colonies (Fig 1). Our observations are the first of F. lemani in a plesiobiontic relationship with another ant species. However, some of Morley’s (1945) observations of plesiobiontic F. fusca may represent misidentified F. lemani since the observations were made prior to Yarrow’s (1954) revision. Nevertheless our observations represent the first confirmed case of F. lemani in a plesiobiontic relationship with another ant species, providing further evidence for Collingwood’s (1979) claim that the habits of F. lemani are similar to F. fusca – the most frequently recorded plesiobiont in the Palearctic region (Kaniszai et al., 2013). Workers of Formica lemani and Lasius flavus differ markedly in size and foraging behaviour. Whereas F. lemani is a free-living and active predacious, aphidicolous and nectarivorous species, L. flavus is mostly subterranean and feeds on smaller arthropods and honeydew from root feeding aphids (Collingwood, 1979; Douwes et al., 2012). The resources exploited by each species thus show little overlap, permitting coexistence without competition. This follows the general pattern outlined for plesiobiontic relationships by Kanizsai et al. (2013). Colony sizes of the two species are listed in the literature as a few Hundred to a few thousand for F. lemani and up to 100 000 workers for L. flavus (Douwes et al., 2012). On the landscape level at the study site at Lygra, our observation matches well with Czechowski’s (2004) suggestion that plesiobiontic nests develop when the limiting factor controlling ant abundances is nesting site availability rather than food resources. Our study area is dominated by Calluna vulgaris heathlands with scattered moorlands, and all ant colonies we found were limited to a small rocky outcrop. It is thus likely that plesiobiontic relationships are common in the area, and further plesiobiont associations may well be observed here in the future. GM Kvifte, TA Legøy, J Soulé – Plesiobiosis between Formica lemani and Lasius flavus368 Acknowledgements The fieldwork happened during a student field course arranged by the University of Bergen, lead by John- Arvid Grytnes. We are indebted to him for encouragement and advice, and to our BIO102 students for helping us searching for ant nests in the field. Finally, we are grateful to Frode Ødegaard, Norwegian Institute for Nature Research, Trondheim, for controlling our identifications of Formica lemani. Comments from two anonymous reviewers helped improve the manuscript. References Collingwood, C.A. 1979: The Formicidae (Hymenoptera) of Fennoscandia and Denmark. Fauna Entomologica Scandinavica, 8: 1-174. Czechowski, W. 2004: Scarcity of sites suitable for nesting promotes plesiobiosis in ants (Hymenoptera: Formicidae). Entomologica Fennica, 15: 211-218. Retrieved from http://www. entomologicafennica.org/Volume15/EF_15_4/3Czechowski. pdf Douwes, P., Abenius, K., Cederberg, B., Wahlstedt, U., Hall, K., Starkenberg, M., Reisborg, C. & Östman, T. 2012: Nationalnyckeln till Sveriges flora och fauna. Steklar: Myror- getingar. Hymenoptera: Formicidae-Vespidae. Uppsala: ArtDatabanken, SLU, 382 pp. Kanizsai, O., Lörinczi, G. & Gallé, L. 2013: Nesting Associations without Interdependence: A preliminary review of plesiobiosis in ants. Psyche, 2013: 238602. doi: 10.1155/2013/238602 Morley, D.W. 1945: Observations on some plesiobiotic colonies of ants (Hymenoptera), with notes on some other mixtobiotic colonies. Proceedings of the Royal Entomological Society of London, 20: 1-4. doi:10.1111/j.1365-3032.1945.tb01041.x Yarrow, I.H.H. 1954: The British ants allied to Formica fusca L. (Hym., Formicidae). Transactions of the Society for British Entomology, 11: 229-244.