Tuesday, January 22, 2013

DNA Barcoding reveals a hybrid

Doesn't that sound strange to you?

For years we have emphasized that hybridisation can complicate the use of DNA-based approaches for species identification such as DNA Barcoding. The fact that we are using a fragment of the mitochondrial genome that is almost exclusively inherited maternally can lead to results were two species seemingly share a DNA Barcode despite all morphological differences. However, the complicating effects of hybridisation are not restricted to DNA-based identification methods; they can also strongly affect morphological identification. As a matter of fact hybrids can be different enough from both parent species to gain description as a distinct species.

Modified from Rougerie et al. 2012
A neat litte study just published in Invertebrate Systematics shows that DNA Barcodes can actually help to unravel such problems. An initial discordance between morphological identifications and the cohesiveness of DNA barcode clusters provoked deeper investigation of the situation with both a nuclear marker and morphology. Paratypes of the hawkmoth species Gnathothlibus collardi possessed a barcode sequence identical to that of Philodila astyanor. Furthemore Gnathothlibus collardi resembles Gnathothlibus eras at first glance. The best possible explanation for this after contamination or other technical errors were ruled out was that Gnathothlibus collardi specimens represent F1 hybrids between Philodila astyanor females and male Gnathothlibus eras. Examination of the D2 region of the 28S rDNA gene and a more thorough morphological reexamination of specimens of the three species then confirmed the findings. A taxonomist had described an invalid species from a hybrid.

Who would have thought that well tended DNA Barcode libraries may one day contribute to the early detection of hybridisation?

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