Abstract
Emergence from an aquatic environment to the land is one of the major evolutionary transitions within the arthropods. It is often considered that the first hexapods, and in particular the first springtails, were semi-aquatic and this assumption drives evolutionary models towards particular conclusions. To address the question of the ecological origin of the springtails, phylogenetic analyses by optimization alignment were performed on D1 and D2 regions of the 28S rDNA for 55 collembolan exemplars and eight outgroups. Relationships among the orders Symphypleona, Entomobryomorpha and Poduromorpha are inferred. More specifically, a robust hypothesis is provided for the subfamilial relationships within the order Poduromorpha. Contrary to previous statements, the semi-aquatic species Podura aquatica is not basal or 'primitive', but well nested in the Poduromorpha. The analyses performed for the 24 different weighting schemes yielded the same conclusion: semi-aquatic ecology is not ancestral for the springtails. It is a derived condition that evolved independently several times. The adaptation for semi-aquatic life is better interpreted as a step towards independence from land, rather than indication of an aquatic origin.
Full Text
The Full Text of this article is available as a PDF (347.6 KB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Averof M., Cohen S. M. Evolutionary origin of insect wings from ancestral gills. Nature. 1997 Feb 13;385(6617):627–630. doi: 10.1038/385627a0. [DOI] [PubMed] [Google Scholar]
- Sanger F., Nicklen S., Coulson A. R. DNA sequencing with chain-terminating inhibitors. Proc Natl Acad Sci U S A. 1977 Dec;74(12):5463–5467. doi: 10.1073/pnas.74.12.5463. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Villani M. G., Allee L. L., Díaz A., Robbins P. S. Adaptive strategies of edaphic arthropods. Annu Rev Entomol. 1999;44:233–256. doi: 10.1146/annurev.ento.44.1.233. [DOI] [PubMed] [Google Scholar]
- Winnepenninckx B., Backeljau T., De Wachter R. Extraction of high molecular weight DNA from molluscs. Trends Genet. 1993 Dec;9(12):407–407. doi: 10.1016/0168-9525(93)90102-n. [DOI] [PubMed] [Google Scholar]