Die Morphologie der Trichoptera im Zeitalter der Phylogenomik - ein innovativer evolutionsbiologischer Ansatz zur strukturellen und verhaltensbiologischen Komplexität der Köcherfliegen (Insecta: Holometabola)
Zusammenfassung der Projektergebnisse
In this project, we studied the morphology of larval, pupal and adult trichopterans, with special focus on soft tissues. Goals were the clarification of controversially discussed structural homology, the reconstruction of the backbone phylogeny of Trichoptera and subsequently the reconstruction of the evolution of major morphological and behavioral traits within the order. The five “spicipalipian” families played a crucial role in these investigations. Altogether, 24 species representing 18 families were investigated using a multiple method approach (µCT, histology, LM, SEM, TEM). In addition to our primary plan, it was necessary to study the pupal stage for functional interpretations of adult morphology. Furthermore, we used autofluorescence‐based laser‐scanning microscopy to gain detailed information on the sclerotization pattern of skeletal parts. One major achievement was the identification of primary homologies for muscles and sclerites of the larval and adult head. The newly developed muscle terminologies and a clear assignment of the head sclerites of trichopterans to that of generalized insects were the essential basis for comparative anatomical studies and the correct coding of structural observations in data matrices. In this context, data and hypotheses available in the literature were reviewed and evaluated. It became clear that the subdivision of sclerites and/or the fusion of sclerites and/or their subparts caused major problems when species are compared on family level. The comprehensive taxon sampling of the project and the detailed investigation of muscles allowed for the clarification of controversially discussed homology assessments (e.g., mouthparts). In comparison, the evaluation of thoracic structures was more straightforward. Analyses of structure‐function relations yielded unexpected results: Expected modifications of the larval (pro‐)thorax related to the shift from a prognathous to a orthognathous head were not found. The analysis of silk‐producing structures and larval legs yielded no specific adaptions in relation to the different use of silk. Instead, behavioral adaptions are the main motors of silk‐use evolution. The 3D‐morphometric analysis of larval mandibles clearly showed that the shape of this mouthpart reflects its high functional constrains. The shape is not useful for phylogenetic purposes but can help to reconstruct the feeding behavior of larvae with unknown diet. The analysis of adult specimens of known age obtained by rearing two species (Hydropsyche, Limnephilus) enabled us to clarify the heterogeneity observed for mandibular muscles (well‐developed or lacking) and wing base muscles (absent/present). The analysis of the volume of the mandibular muscle based on µCT data sets showed for the first time that the muscles are reduced during aging of the adult. It is now clear that the observed anatomical differences are based on specimens of different age and that the “lack” of mandibular muscles is not of phylogenetic value. Similar results were acquired for the wing base muscles. The intended analysis of our morphological data (matrix) in the framework of the 1KITE Trichoptera subproject was impeded by some issues with the molecular data. However, the parsimony analysis of the morphological data resulted in a well‐resolved backbone phylogeny of Trichoptera with the pattern Annulipalpia + (Rhyacophiloidea + (Glossosomatidae + (Hydroptiloidea + Integripalpia))). All nodes are well‐supported by a series of new apomophies. Based on this topology we were able to reconstruct the morphological and behavioral groundplan condition of Trichoptera. Our data favor that the larva of the last common ancestor was free‐living (no larval case), primarily predacious and inhabited cool, running waters. Within Annulipalpia, the larvae shifted to passive filter‐feeding and constructed fixed retreats. The larval cases of (Integripalpia + Hydroptiloidea) + Glossosomatidae are a potential apomorphy of the clade but developed independently from annulipalpian retreats. With the data at hand is seems plausible to assume that the larval cases are derived from pupal shelters which are produced by all caddisfly larvae. During evolution, this structure is also produced by earlier larval instars in the case‐building forms. This was an important step in trichopteran evolution and a major key to the radiation of integripalpian groups.
Projektbezogene Publikationen (Auswahl)
- (2013) Insect morphology in the phylogenomic age – its impact on the reconstruction of phylogeny and evolution. 106. Jahrestagung der Deutschen Zoologischen Gesellschaft in Munich, September 13 ‐ 16, 2013
Friedrich, F.
- (2013) The head anatomy of adult caddisflies (Insecta: Trichoptera) revealed by SR‐μCT. Hasylab Annual Report 2012
Kubiak, M., Wilde, F., Beckmann, F. & Friedrich, F.
- (2014) The anatomy of caddisfly larvae (Insecta: Trichoptera) investigated by SR‐μCT at PETRA III. Hasylab Annual Report 2013
Friedrich, F., Kubiak, M., Wilde, F. & Beckmann, F.
- (2015) The adult head of the annulipalpian caddisfly Philopotamus ludificatus McLachlan, 1878 (Insecta: Trichoptera: Philopotamidae), mouthpart homology and phylogenetic implications. Arthropod Systematics & Phylogeny 73(3): 351‐384
Kubiak, M., Beckmann, F. & Friedrich, F.
- (2015) The larval head anatomy of Rhyacophila (Rhyacophilidae) with discussion on mouthpart homology and the groundplan of Trichoptera. Journal of Morphology 276(12): 1505‐1524
Friedrich, F., Schulz, J., Kubiak, M., Beckmann, F. & Wilde, F.
(Siehe online unter https://doi.org/10.1002/jmor.20475) - (2015) The larval head anatomy of Rhyacophila fasciata Hagen 1859 and its implications on mouthpart homology and the phylogeny of Trichoptera. 15th International Trichoptera Symposium in New Brunswick/USA, June 4 ‐ 7, 2015
Friedrich, F., Schulz, J. & Kubiak, M.
- (2016) Comparative head anatomy of larval caddisflies with implications on mouthpart homology and the evolution of Trichoptera. 25th International Congress of Entomology in Orlando/USA, September 25 ‐ 30, 2016
Friedrich, F.
- (2016) The morphology and evolution of adult head structures in Trichoptera (Insecta). Universität Hamburg
Kubiak, M.
- (2017) Comparative larval and adult head anatomy of caddisflies with implications on the phylogeny of Trichoptera. 8th Dresden Meeting on Insect Phylogeny, September 22 ‐ 24, 2017
Friedrich, F. & Kubiak, M.
