Delimitation difficulties in species splits: a morphometric case study on the Euxoa tritici complex (Lepidoptera, Noctuidae)

Abstract

Genital characteristics tend to vary greatly between Lepidoptera species, providing helpful features for species delimitation. The differences between species are usually remarkable and suspicions about species identity never arise. However, fairly often, and possibly increasingly, taxa are elevated to species rank on the basis of very slight morphological differences, often without quantitative support. Euxoa tritici (Linnaeus) is a typical example of a variable species split into several morphologically similar species. The present study tested whether the diagnostic genital characters of the current classification, based on nonquantitative methodology, provide safe identification of species. Both traditional distance morphometrics as well as modern geometric morphometrics, which also enables quantitative shape exploration, were used. Moreover, whether the study specimens can be unambiguously categorized into several species with visual comparisons was tested independently using four specialist entomologists. Genital types of several named species as well as considerable variation in genitalia were found, but no support was found for the presence of several morphologically distinguishable species with quantitative morphometric analyses. Neither were study specimens categorized unambiguously by specialists. The results suggest that pure visual comparisons may lead to unsound taxonomic conclusions and that a quantitative approach in critical cases should be used more frequently.

Evaluation of criteria for species delimitation of bagworm moths (Lepidoptera: Psychidae)

“…As in other studies on Lepidoptera (Mutanen, 2005;Mutanen et al, 2007;Dapporto, 2008Dapporto, , 2010, we demonstrate that differences in male genitalia are an effective way of discriminating between species of the genera Dahlica and Siederia. In fact, the extensive use of geometric morphometrics to search for differences among taxa is strongly recommended by Mutanen & Pretorius (2007).…”

Two Species withinDendroctonus frontalis(Coleoptera: Curculionidae): Evidence from Morphological, Karyological, Molecular, and Crossing Studies

“…Robustness of these clusters was demonstrated when D. vitei and D. mexicanus (species with a high morphological similarity with D. frontalis) were incorporated into the analysis and the inclusion of these additional samples did not disrupt the original clusters corresponding to each morphotype. Multivariate analysis has been used extensively to identify and delimit morphological and genetic variation within and between species (Doyen 1973, Doyen and Slobodchikoff 1974, Mutanen 2005, Adeleke et al 2008, Jeffrey et al 2008, Padial and De la Riva 2009, Thorpe 2010.…”

Wing Shape as an Indicator of Larval Rearing Conditions forAedes albopictusandAedes aegypti(Diptera: Culicidae)

“…It has been used to investigate physiological changes between different populations of Triatomines (Jaramillo et al 2002, Schachter-Broide et al 2004) and tsetse flies (Bouyer et al 2007). This method is also frequently used to solve taxonomic problems, where it can provide support for proposed changes in taxonomic status or call into question previously accepted classifications (e.g., Baylac et al 2003, Mutanen 2005). It can also serve as an inexpensive, reliable, one-step way to identify members of otherwise morphologically similar species (Villemant et al 2007).…”