Thursday, August 13, 2009


ResearchBlogging.orgCame across this article in the New Scientist. It's a lovely piece of modern day molecular biology doing some forensic work to rediscover a species that was thought to have died out a couple of hundred years ago. The bird in question is the Tasman Booby (Sula tasmani).

It has been speculated that this bird has been extinct since around 1790, though evidence has suggested that these birds might still be around. From my reading of the papers, it appears that the call for extinction of the Tasman Booby was based on the examination of fossil material. However the authors believe that the previous study was instead looking at fossil remains of S. dactylatra, the Masked Booby, that were in the upper size range of that species.

The authors first performed morphometric data. Their results were presented as follows:
Contrary to van Tets et al. (1988), our comparison of new skeletal material revealed a size overlap between modern and fossil specimens for all standard humerus measurements.
Such an overlap was not seen by van Tets et al. (see Table 1 reproduced below).So how does that happen? The authors of this manuscript state that van Tets et al. in their studies made a bit of a faux pas. Seems that they "failed to acknowledge" the fact that all the fossil specimens in their study were female, and the modern specimens in their study were male. Like a number of birds, the Booby presents with what is known as reversed sexual size dimorphism. In other words, the females are larger than the males. Whoops.

Anywhoo ... Steeves et al. complement the morphometric data with genetic data by performing mitochondrial DNA sequencing. Phylogenetic analysis of these sequences revealed that mitochondrial DNA extracted from three of the six fossil specimens (nothing was recoved from the remaining fossils) were identical to an existing species of Booby, Sula dactylatra fullagari. Based on this, they proposed that all North Tasman Sea boobies should be known as Sula dactylatra tasmani. With this Steeves et al. have extracted the Tasman Booby from the Book of the Dead!

Steeves, T., Holdaway, R., Hale, M., McLay, E., McAllan, I., Christian, M., Hauber, M., & Bunce, M. (2009). Merging ancient and modern DNA: extinct seabird taxon rediscovered in the North Tasman Sea Biology Letters DOI: 10.1098/rsbl.2009.0478

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