Expert: Dana Krempels, Ph.D. - 10/3/2009

Question
Hi,
Can you tell me how molecular information is used to determine which of the stickleback types were oldest?

Thanks,


Answer
Dear Shobana,

Molecular information can be of various types, from protein sequence data to DNA or RNA sequence data.  But whatever type you're using, and whatever type of organisms you're studying, such data can be used to determine which lineage of your study taxon is oldest by comparing similar data from an OUTGROUP:  the taxon most closely related to the study taxon, but not actually included within it.

For example, if you were studying DNA sequences or protein sequences of the Great Apes (orangutans, gorillas, chimpanzees, and humans), then your outgroup would the the next most primitive, related group, the gibbons (Lesser Apes).  If if you were studying all the apes, then a reasonable outgroup might be an Old World Monkey (e.g., baboon).

So what you need to determine first is the outgroup most appropriate for comparison to sticklebacks:  the sister taxon to all sticklebacks (Gasterosteidae). I'm no stickleback expert, but I did a quick search and this group appears to be a bit of a taxonomic puzzle.  You can see a few links of interest here:

http://books.google.com/books?id=4s1FnZ9f_aAC&pg=PA338&lpg=PA338&dq=Gasterosteid...

http://www.ncbi.nlm.nih.gov/pubmed/14715228

and just a big ol' wad of scholarly information on the molecular taxonomy of this family from a Google search:

http://www.google.com/#hl=en&q=Gasterosteidae+molecular+&aq=f&aqi=&aq=&aqi=&aq=f...

Hope that's helpful!

Dana