DNA Taxonomy and the identification of immature insect stages: the true larva ofTauriphila argo(Hagen 1869) (Odonata: Anisoptera: Libellulidae)

Abstract

For many insect taxa, larval morphology plays a decisive role in various fields like taxonomy, phylogeny or ecology. However, species identification is usually based on imaginal characters and the identification of larvae depends upon an established link to unequivocally identified imagines. This taxonomic correspondence of larvae and imagines is far from being established in many odonate species. We have employed a molecular approach to link larval and adult specimens in Tauriphila argo (Hagen, 1869). The sequenced mt SSU gene fragments of the reared female, supposedly a T. argo female, and a clearly identified male specimen of the species were identical. However, the larva of the reared female clearly differed from the described T. argo larva, previously matched to the species. From this observation, we conclude that the previously described larva of T. argo does not belong to this species because of too many phenotypic differences that far exceed the generally observed intraspecific variation. It can be foreseen that the molecular approach will prove to be effective in identifying unknown larvae in many insect species. Additionally, the discrimination of sibling species or the linkage of allotypes and holotypes will become feasible with this approach. Résumé. Taxonomie ADN et identification des stades larvaires : la véritable larve de Tauriphila argo (Hagen 1869) (Odonata : Anisoptera : Libellulidae).La connaissance des larves de certains groupes d'insectes s'avère importante dans des domaines aussi variés que la taxonomie, la phylogénie ou l'écologie. Or la correspondance entre la larve et l'adulte est loin d'être établie pour la majorité des espèces. Jusqu'à présent la seule méthode pour réaliser ce lien est d'élever la larve jusqu'à l'obtention de l'imago. Cette méthode est longue, fastidieuse et n'aboutit pas toujours. Nous avons utilisé l'outil moléculaire pour établir ce lien en comparant les séquences ADN de deux spécimens. Cet outil peut également s'avérer très efficace pour discriminer des espèces jumelles ou faire correspondre un type mâle avec une femelle supposée appartenir à la même espèce. C'est grâce à cet outil que nous avons pu déterminer de façon sûre la larve de Tauriphila argo (Hagen, 1869). La larve précédemment décrite attribuée à T. argo ne devrait pas appartenir à cette espèce étant donné le nombre important de différences qui dépasse de loin celui d'une simple variation intraspécifique.

Association of nymphs and adults of Ephemeroptera (Insecta) using the amplified fragment length polymorphism (AFLP) technique

“…1), and every terminal branch at the species level was supported 100% by bootstrap analysis, regardless of the location where they were collected. This result was in agreement with the association between larva and adult stages in other insects, when gene sequences were used (Miller et al, 2005(Miller et al, , 2007Fleck et al, 2006;Jeon and Ahn, 2007). In this research, the AFLP technique revealed advantages in relation to other molecular techniques; for instance, previous knowledge about the gene sequence of the organisms studied was not necessary and allowed exploration and comparison of the whole genome, despite its moderate cost (Ferna´ndez-Cuenca, 2004;Meudt and Clarke, 2007).…”

“…In these orders, the species identification is usually based on adults; the nymph does not present sufficient morphological characteristics for identification at the species level, and the identification depends on an established link to unequivocally identified imagines (Fleck et al, 2006;Stark et al, 2009). Given the successful association of these specimens through the AFLP technique, similar success may be expected in associating the adults and nymphs of other insect groups.…”

“…There are currently different molecular biology techniques that have used DNA as a taxonomic character in the association of immature and adult stages of insects (Miller et al, 2005(Miller et al, , 2007Fleck et al, 2006;Jeon and Ahn, 2007). For example, Miller et al (2005) developed strategies for the association of unknown larvae and known adults of Dytiscidae (Coleoptera) using DNA sequence data, with an 806-bp portion of the gene cytochrome oxidase I.…”

“…In 2007, Jeon and Ahn used the partial cytochrome oxidase II gene (375 bp) to associate unknown larvae and identified adults of the Staphilinidae (Coleoptera). Fleck et al (2006) used mitochondrial SSU rRNA gene fragments to associate unidentified larvae and described adults of Libellulidae (Odonata: Anisoptera). These works have confirmed that molecular techniques constitute useful tools for the determination of unknown stages of life in species of insects.…”

Larval development and growth ratios of Odonata of the Azores

“…It is often difficult to identify the larval stages of many species (Fink 1984;Skuhrovec 2006), particularly during the early phases of life when successive instars can overlap in size and the larvae of related species are usually indistinguishable (e.g. Fleck et al 2006).…”