Proteomic comparison of two invasive polychaete species and their naturally occurring F1-hybrids.

The mud worm genus Marenzelleria is highly invasive and is therefore studied intensively. In recently invaded habitats, sympatric populations of the sibling species Marenzelleria viridis and Marenzelleria neglecta are found. In these secondary contact zones, hybridization occurs frequently, revealing incomplete reproductive isolation between these recently diverged species. Two-dimensional polyacrylamide gel electrophoresis (2-DE) and mass spectrometric methods were applied for a comparative analysis of these species and their F(1)-hybrids. Nineteen proteins were identified by cross-species identification strategies. A low degree of interindividual variability within either species allowed characterizing qualitative species-specific differences in 2-DE spot patterns as well as in peptide maps. Species-specific peptides were found in tryptic digests of various proteins, such as glyceraldehyde-3-phosphate dehydrogenase, troponin C, gelsolin-like protein, and peroxiredoxin-1. F(1)-hybrids of M. viridis and M. neglecta showed additivity of protein spot patterns, and the presence of both parental traits was confirmed by mass spectrometric data. This study is one of few dealing with global protein expression in polychaetes and is the first proteomic description of natural F(1)-hybrids in polychaetes. It furthermore indicates the feasibility of proteomic methods for analyses of speciation in Marenzelleria siblings as well as of hybridization events in secondary contact zones in general.