A discrete neuropeptide difference between two hybridizing grasshopper subspecies

Progress, pitfalls and parallel universes: a history of insect phylogenetics

The phylogeny of insects has been both extensively studied and vigorously debated for over a century. A relatively accurate deep phylogeny had been produced by 1904. It was not substantially improved in topology until recently when phylogenomics settled many long-standing controversies. Intervening advances came instead through methodological improvement. Early molecular phylogenetic studies (1985-2005), dominated by a few genes, provided datasets that were too small to resolve controversial phylogenetic problems. Adding to the lack of consensus, this period was characterized by a polarization of philosophies, with individuals belonging to either parsimony or maximum-likelihood camps; each largely ignoring the insights of the other. The result was an unfortunate detour in which the few perceived phylogenetic revolutions published by both sides of the philosophical divide were probably erroneous. The size of datasets has been growing exponentially since the mid-1980s accompanied by a wave of confidence that all relationships will soon be known. However, large datasets create new challenges, and a large number of genes does not guarantee reliable results. If history is a guide, then the quality of conclusions will be determined by an improved understanding of both molecular and morphological evolution, and not simply the number of genes analysed.

Extended FMRFamides in dipteran insects: conservative expression in the neuroendocrine system is accompanied by rapid sequence evolution

Extended FMRFamides are found throughout the central nervous system (CNS) of insects and exhibit diverse physiological effects on different target organs, such as muscles, intestine, and the nervous system. The genes encoding for extended FMRFamides are known from a number of flies, including Drosophila species, and the pest insects Lucilia cuprina, Calliphora vomitoria, and Musca domestica. No data, however, exist about the expression of the numerous paralogs of the latter three species, and studies on Drosophila melanogaster resulted in controversial findings. We could unambiguously verify, that all predictable products of the extended FMRFamide precursor are expressed in neurohemal tissues of the thoracic neuromers of these flies and can easily be identified and also sequenced by using single specimens. In addition to the confirmation of extended FMRFamides in species with known precursor sequences, the current knowledge about homologous peptides of Sarcophaga (=Neobellieria) bullata could be extended by de novo sequencing using tandem mass spectrometry. The most intriguing finding in this study was the detection of an internal gene duplication, followed by an amino acid substitution, in an insecticide-resistant strain of L. cuprina. To our knowledge, this is the first detection of such an intraspecific event and confirms the low conservation of the extended FMRFamide gene sequences. In insects, no other neuropeptide family is known that shows such sequence variability between related species.

A proteomic approach for studying insect phylogeny: CAPA peptides of ancient insect taxa (Dictyoptera, Blattoptera) as a test case

Background

Neuropeptide ligands have to fit exactly into their respective receptors and thus the evolution of the coding regions of their genes is constrained and may be strongly conserved. As such, they may be suitable for the reconstruction of phylogenetic relationships within higher taxa. CAPA peptides of major lineages of cockroaches (Blaberidae, Blattellidae, Blattidae, Polyphagidae, Cryptocercidae) and of the termite Mastotermes darwiniensis were chosen to test the above hypothesis. The phylogenetic relationships within various groups of the taxon Dictyoptera (praying mantids, termites and cockroaches) are still highly disputed.

Results

Tandem mass spectrometry of neuropeptides from perisympathetic organs was used to obtain sequence data of CAPA peptides from single specimens; the data were analysed by Maximum Parsimony and Bayesian Interference. The resulting cladograms, taking 61 species into account, show a topology which is in general agreement with recent molecular and morphological phylogenetic analyses, including the recent phylogenetic arrangement placing termites within the cockroaches. When sequence data sets from other neuropeptides, viz. adipokinetic hormones and sulfakinins, were included, the general topology of the cladogram did not change but bootstrap values increased considerably.

Conclusion

This study represents the first comprehensive survey of neuropeptides of insects for solely phylogenetic purposes and concludes that sequences of short neuropeptides are suitable to complement molecular biological and morphological data for the reconstruction of phylogenetic relationships.