Giant ants and their shape: revealing relationships in the genus Titanomyrma with geometric morphometrics

• Published in: PeerJ (San Francisco, CA) Vol. 6; p. e4242
• Main Authors: Katzke, Julian, Barden, Phillip, Dehon, Manuel, Michez, Denis, Wappler, Torsten
• Format: Journal Article
• Language: English
• Published: United States PeerJ. Ltd 16.01.2018; PeerJ, Inc; PeerJ Inc
• Subjects: Analysis; Ants; Biodiversity; Eckfeld; Ecology; Entomology; Evolution; Formicidae; Formiciinae; Formicinae; Formicium; Formicium brodiei; Fossils; Hymenoptera; Identification and classification; Males; Messel; Mitochondrial DNA; Morphology; Morphometrics (Biology); Morphometry; Palaeoentomology; Palaeontology; Paleontology; Phylogenetics; Physiological aspects; Species; Taxonomy; Wings; Fossil ants; Palaeoentomology; Formicidae; Eckfeld; Formiciinae; Messel; Formicium; Wing venation; Palaeontology
• ISSN: 2167-8359; 2167-8359
• DOI: 10.7717/peerj.4242

Shape is a natural phenomenon inherent to many different lifeforms. A modern technique to analyse shape is geometric morphometrics (GM), which offers a whole range of methods concerning the pure shape of an object. The results from these methods have provided new insights into biological problems and have become especially useful in the fields of entomology and palaeontology. Despite the conspicuous successes in other hymenopteran groups, GM analysis of wings and fossil wings of Formicidae has been neglected. Here we tested if landmarks defining the wing shape of fossil ants that belong to the genus are reliable and if this technique is able to expose relationships among different groups of the largest Hymenoptera that ever lived. This study comprises 402 wings from 362 ants that were analysed and assigned with the GM methods linear discriminant function analysis, principal component analysis, canonical variate analysis, and regression. The giant ant genus and the parataxon have different representatives that are all very similar but these modern methods were able to distinguish giant ant types even to the level of the sex. Thirty-five giant ant specimens from the Eckfeld Maar were significantly differentiable from a collection of Messel specimens that consisted of 187 females and 42 males, and from 74 females and 21 males. Out of the 324 Messel ants, 127 are newly assigned to a species and 223 giant ants are newly assigned to sex with GM analysis. All specimens from Messel fit to the two species. Moreover, shape affinities of these groups and the species , , and , which are known only from wings, were investigated. stands out with a possible female relative in one of the Eckfeld specimens whereas the other groups show similar shape patterns that are possibly plesiomorphic. Formicidae are one of the most dominant taxa in the animal kingdom and new methods can aid in investigating their diversity in the present and in deep time. GM of the ant wing delivers significant results and this core of methods is able to enhance the toolset we have now to analyse the complex biology of the ants. It can prove as especially useful in the future when incorporated into better understanding aspects of evolutionary patterns and ant palaeontology.