Question about criteria for mouse subspecies identification

I’m not sure where to ask this so if this is the wrong place, please point me in the right direction!

This is a question about iNaturalist criteria for identifying subspecies that are extremely similar visually - in particular Mus musculus domesticus, aka the Western European house mouse. (For non-mouse people, this is the subspecies that pet mice are derived from.)

A wild-type, agouti colored Mus musculus would generally need DNA analysis to confirm the subspecies. Should every Mus musculus observed comfortably within the subspecies’ range be identified as such? It seems like the alternative is never including the subspecies in the ID.

Map source:

More background info:

It is an interesting question.

Personally, I don’t do this or think it’s a good use of time since it isn’t adding any new information to only ID based on location (the location is already in the observation data) and might lead to cases where a different subspecies is ignored/missed/misidentified. That is, IDing by location only is a sort of positive feedback loop that just reinforces/concretizes existing knowledge about ranges (and that data may not always be correct or those ranges may be changing/fluid…)

The issue has come up on several other forum posts that may help out:


Thanks for the links to previous discussions!

So I guess the takeaway is, I shouldn’t bother trying to refine the IDs down to subspecies, but it might be a good idea to disagree with existing subspecies IDs if they’re far away from their known range, by suggesting it be identified at the species level instead. Sounds like a plan.


Was that the criterion by which the subspecies were described in the first place? In cases like this, I always think it best to go by the subspecies description. And if that is not useful visually, I would question the existence of subspecies in the first place.

As I remember different Acomys species were divided by DNA only (there was geographic separation too, but otherwise similar for us humans animals), so subspecies of domestic mice also could be divided this way, especially if there is a map for them (how useful it is though?).

The answer to your question is in Section 2.3.3 of the JAX link (source for the subspecies map):

" If, as the one-species protagonists claim, musculus and domesticus mice simply arrived in Europe and spread toward the center by different routes — domesticus from the southwest and musculus from the east — then upon meeting in the middle, the expectation would be that they would readily mix together. This should lead to a hybrid zone which broadens with time until eventually it disappears. In its place initially, one would expect a continuous gradient of the characteristics present in the original two groups.

In contrast to this expectation, the European hybrid zone does not appear to be widening. Rather, it appears to be stably maintained at a width of less than 20 kilometers (Sage et al., 1986). Since hybridization between the two groups of mice does occur in this zone, what prevents the spreading of most genes beyond it? The answer seems to be that hybrid animals in this zone are less fit than those with pure genotypes on either side."


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