I'm trying to get my head round some locally important species, and as usual Lichens are causing me some headaches. So I am trying to decide how to assign a local importance to Caloplaca herbidella.

I would usually find the Recommended_Taxon_List_Item Key in Index_Taxon_Name (ITN) and use it to get the Preferred_Taxon_Version_Key (pTVK). This works fine with 95% of the names I look up, but occasionally I have to check the Taxon Rank to avoid allocating an 'Agg.' rather than the species (or vice versa).

With Caloplaca herbidella, there are two RTLIK choices in ITN:
NHMSYS0020980684 and NHMSYS0000357670
thus giving me to pTVKs:
NHMSYS0020987556 and NBNSYS0000039595

In both cases these appear to point at true species names not forms, aggs, sub species or varieties.

Using the go To Key Add-in, I can only get to  a species from NHMSYS0020980684 - the other one doesn't seem to go anywhere (although it is in the dictionary!). The add-in recognises that NHMSYS0000357670 is a Lichen, but does not take me to a species (or form, synonym etc). So clearly R6 wants me to use NHMSYS0020980684 (and thus pTVK = NHMSYS0020987556), but why then are there two choices of RTLIK in ITN? Or is this just something that no-one has got around to updating yet?

For my purposes I'll use both pTVKs just to be on the safe side, but this anomaly intrigues me.

Regards,
Dave