title: Near-infrared imaging spectroscopy as a tool to discriminate two cryptic Tetramorium ant species.
abstract: Correct species identification is a precondition for many ecological studies. Morphologically highly similar, i.e., cryptic, species are an important component of biodiversity but particularly difficult to discriminate and therefore understudied ecologically. To find new methods for their rapid identification, thus, is important. The cuticle's chemical signature of insects often is unique for species. Near-infrared spectroscopy (NIRS) can capture such signatures. Imaging NIRS facilitates precise positioning of the measurement area on biological objects and high-resolution spatial capturing. Here, we tested the applicability of imaging NIRS to the discrimination of cryptic species by using the ants Tetramorium caespitum and T. impurum. The classification success of Partial Least Squares Regression was 98.8%. Principal Component Analysis grouped spectra of some T. impurum individuals with T. caespitum. Combined with molecular-genetic and morphological evidence, this result enabled us to pose testable hypotheses about the biology of these species. We conclude that discrimination of T. caespitum and T. impurum with imaging NIRS is possible, promising that imaging NIRS could become a time- and cost-efficient tool for the reliable discrimination of cryptic species. This and the direct facilitation of potential biological insight beyond species identification underscore the value of imaging NIRS to ecology.
authors.affiliation: Institute of Ecology, Molecular Ecology, University of Innsbruck, Technikerstraße 25, 6020, Innsbruck, Austria. jasmin.klarica@gmail.com
authors.forename: Jasmin
authors.initials: J
authors.lastname: Klarica
authors.forename: Lukas
authors.initials: L
authors.lastname: Bittner
authors.forename: Johannes
authors.initials: J
authors.lastname: Pallua
authors.forename: Christine
authors.initials: C
authors.lastname: Pezzei
authors.forename: Verena
authors.initials: V
authors.lastname: Huck-Pezzei
authors.forename: Floyd
authors.initials: F
authors.lastname: Dowell
authors.forename: Johannes
authors.initials: J
authors.lastname: Schied
authors.forename: Günther K
authors.initials: GK
authors.lastname: Bonn
authors.forename: Christian
authors.initials: C
authors.lastname: Huck
authors.forename: Birgit C
authors.initials: BC
authors.lastname: Schlick-Steiner
authors.forename: Florian M
authors.initials: FM
authors.lastname: Steiner
mesh_terms: D000818:Animals; D001000:Ants / Q000737:chemistry* / Q000145:classification*; D004772:Entomology / Q000379:methods*; D005060:Europe; D006838:Hydrocarbons / Q000032:analysis / Q000737:chemistry*; D016018:Least-Squares Analysis; D025341:Principal Component Analysis; D019265:Spectroscopy, Near-Infrared
chemical_list: D006838:Hydrocarbons