Say you have access to a lab that can produce DNA-sequences and you have a sample of a crab you cannot identify because some of the key characters are on body parts that have been broken and lost. You produce a DNA-sequence from the “barcode-gene” and open the identification engine in BOLDSYSTEMS.org.
Having submitted your query to BOLD, you wait for some seconds for results. In this example BOLD returned the following window.
The results window lists the top matches in terms of sequence similarity, and in this case we have 100 % similarity match with the crab Atelecyclus rotundatus. There is also an option to display the results as a TREE BASED IDENTIFICATION. When clicking on the option tab, the closest hits are clustered in a so-called Neighbour Joining Tree. In the window below you see parts of the tree where our unknown DNA-sequence has been joined to a group of other sequences in BOLD that have been deposited as Atelecyclus rotundatus barcodes by other biodiversity labs.
The species page for Atelecyclus rotundatus gives us more information about this crab and about its records in BOLD.
If in fact your sequence was produced from an unknown crab, this identification seems convincing. But sometimes you should think twice about search results, and this will be the topic of a future blog post.