Colony-specific Hydrocarbons Identify Nest Mates in Two Species of Formica Ant

Abstract

The possession of a colony identity is a fundamental property that underlies much animal behavior. In insect societies, it is widely accepted that nest-mate recognition cues are encoded within the cuticular hydrocarbons. Despite numerous studies over the past 30years, the identification of these nest-mate specific signatures is only just starting to occur. In this paper, we show two different methods by which nest-mate-specific signatures can be encoded within the hydrocarbon profile of two species of Formica ants. In F. exsecta, nest-mate-specific signatures rely on the distribution of chain lengths of a single type of hydrocarbon, various (Z)-9-alkenes, which are present in colony-specific proportions. In F. fusca, variation in nine different positional isomers of C(25)-dimethylalkanes is sufficient to produce unique colony profiles. By using this information alone, we correctly assigned 97 F. exsecta workers into their respective 20 colonies and 111 F. fusca workers into their respective 30 colonies. These two systems or variations of them may be expected to occur in many insect societies that have a strong colony identity.

A conserved fertility signal despite population variation in the cuticular chemical phenotype of the trap-jaw antOdontomachus brunneus

“…Recent experimental work on cuticular hydrocarbons and nestmate recognition has shown that changes in specific subsets of the overall chemical profile are primarily responsible for distinguishing non-nestmates from nestmates (Greene and Gordon, 2007;Martin et al, 2008a;Martin et al, 2008c;Brandt et al, 2009;Guerrieri et al, 2009;van Wilgenburg et al, 2010). Aggression seems to be triggered by recognizing cuticular profiles as being unfamiliar, and the degree of difference from the colony's template correlates with aggression (Suarez et al, 2002;Ozaki et al, 2005;Guerrieri et al, 2009;Martin et al, 2012;Sturgis and Gordon, 2012).…”

Pattern recognition algorithm reveals how birds evolve individual egg pattern signatures

“…Signatures are common in diverse taxa. They can be chemical, like the hydrocarbon signatures used by Formica ants to recognize nest-mates 3 , or auditory, like the vocalizations used by Australian sea lion (Neophoca cinerea) mothers and pups to reunite in dense colonies 4 , or visual, like the facial patterns used by Polistes fuscatus paper wasps to recognize individuals in the colony 5 . In birds, egg patterns can be visual signatures of offspring identity, enabling parents to recognize their eggs in a crowded colony 6 or to distinguish their own eggs from those of a brood parasitic cheat 7 .…”

A statistical approach to identify candidate cues for nestmate recognition

“…A clear difference in aggression between NMs and nNMs has been observed, even when CHC profiles are quite similar (Martin et al, 2012). The CHC profile is relatively simple and consists of 10-12 (Z)-9-alkenes and linear alkanes (pairwise corresponding in chain-length), of which the composition of alkenes appears to encode the nestmate recognition signal (Martin et al, 2008a), and some additional compounds present in low concentration. The CHC dataset (courtesy of Stephen J. Martin) consisted of 33 colonies from the same population, each containing information on 10 CHCs [(Z)-9-C 23:1 to n-C 31 ] and five individual workers (Martin et al, 2012; Table S1).…”

“…A third strategy is to assess the correlation between compounds (e.g., Martin et al, 2008a), so that we can group covarying compounds directly into homogeneous clusters. Strongly co-varying variables should bring approximately the same information, so reducing the number of variables could simplify further data analysis.…”