When IDing a genus I first try to determine all species ID options for the location including unobserved species, by checking external sources. In cases where it seems there’s one species in a location, I occasionally later come across obscure records of a second. These often lack photos, description, or aren’t mapped to databases, and papers describing them are often dated, making them difficult to evaluate or ask authors about.
In some cases the obscure species doesn’t prove to be relevant, e.g. if it looks different, was a later revised, or was misidentified. But it’s often impossible to know, since it may (even if unlikely) just be uncommon, rare, unconfirmed or dubious yet not disproven, or just rarely studied or sampled/observed. Once learning of an obscure second species record, a maximally cautious approach would be to then only ID genus. I like many mostly do that, but occasionally still tentatively ID the abundant species. The decision depends on how likely or valid you infer the obscure species to be, how far you searched for the answer, and whether the answer is known anywhere (sometimes expert sources share the same uncertainty). In these scenarios do you only ID genus, ID the abundant species, or ID genus and/or species on a case by case discretionary approach? (I do the last.)
One consideration is some users (probably everyone at certain times) don’t always consult external sources but base IDs mostly on current iNat obs. or Place checklists (although which may include unobserved species). Doing so isn’t always ideal, although it’s also true that the most abundant-in-nature and observed species are most likely IDs (and are best-described in external sources). A final scenario is if there’s a single proven record of a species occurring far outside it’s known range and where it isn’t established. If that species is similar to an abundant established species, it can raise the same question of whether to now only ID to genus. Adding to the complexity, we may also consider that rare but undetected out of range species occurrences can or may likely have occurred anywhere. What’s your ID response to out of those out of range scenarios?
The European tube wasp (Ancistroceros gazella) has frequently been IDed in Australia, but external sources also list a second species which has far less accessible photos or ID info by comparison.
iNat and most external source Florida, US records only include one mouse eared bat (Myotis austroriparius), but GBIF includes a single older and potentially unlikely or unconfirmed record of a second eastern US species.
Hawaii, US was once thought to only have three metallic sweat bees (Dialictus), but it’s since become unclear whether there could now be additional.
The potter wasp Oreumenoides edwardsii which has been observed on iNat was once-reported by an external source to have been sighted far outside it’s known Asian range.