Saturday, June 02, 2012

Linking NCBI taxonomy to GBIF

In response to Rutger Vos's question I've started to add GBIF taxon ids to the iPhylo Linkout website. If you've not come across iPhylo Linkout, it's a Semantic Mediawiki-based site were I maintain links between the NCBI taxonomy and other resources, such as Wikipedia and the BBC Nature Wildlife finder. For more background see

Page, R. D. M. (2011). Linking NCBI to Wikipedia: a wiki-based approach. PLoS Currents, 3, RRN1228. doi:10.1371/currents.RRN1228

I'm now starting to add GBIF ids to this site. This is potentially fraught with difficulties. There's no guarantee that the GBIF taxonomy ids are stable, unlike NCBI tax_ids which are fairly persistent (NCBI publish deletion/merge lists when they make changes). Then there are the obvious problems with the GBIF taxonomy itself. But, if you want a way to generate a distribution map for a taxon in the NCBI taxonomy, the quickest way is going to be via GBIF.

The mapping is being made automatically, with some crude checks to try and avoid too many erroneous links (e.g., due to homonyms). It will probably take a few days to complete (the mapping is quick, uploading to the wiki is a bit slower). Using a wiki to manage the mapping makes it easy to correct any spurious matches.

As an example, the page is for the frog Hyla japonica (NCBI tax_id 109175) and shows links to Wikipedia (, and to GBIF ( There's even a link to TreeBASE. I display a GBIF map so you can see what data GBIF currently has for that taxon.


So, we have a wiki page, how do we answer Rutger's original question: how to get GBIF occurrence records via web service?

To do this we can use the RDF output by the Semantic Mediawiki software that underpins the Wiki. You can gte this by clicking on the RDF icon near the bottom of the page, or go to The RDF this produces is really, really ugly (and people wonder why the Semantic Web has been slow to take off...). In this RDF you will see the statement:

<rdfs:seeAlso rdf:resource=""/>

So, arm yourself with XPath, a regular expression, or if you are a serious RDF geek break out the SPARQL, and you can extract the GBIF taxon id for a NCBI taxon. Given that id you can query the GBIF web services. One service that I like is the occurrence density service, which you can use to recreate the 1°×1° density maps shown by GBIF. For example, will get you the squares shown in the screen shot above.

Of course, I have glossed over several issues, such as the errors and redundancy in the GBIF classification, the mismatch between NCBI and GBIF classifications (NCBI has many more ranks than GBIF), and whether the taxon concepts used by the two databases are equivalent (this is likely to be more of an issue for higher taxa). But it's a start.