How do you approach observations where some IDers say the evidence is lacking on key traits but others say there is no other species it could be?

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Although I understand what quantifies as gold standard in provable IDs (say genitalia in spiders except in very rare cases) and other sides of what fits best given current evidence. I routinely see this same discussion popping up in my IDs.

To give one recent example on a morphometrics argument for Palp footed spider - https://www.inaturalist.org/observations/329432914 , I understand there are mutiple arguments for any ID and each inat IDer may fall in their own stance spectrum, I just want to hear what other IDers opinions here are for similar cases in even their own domains and relevant discussions they have when met with “sufficiency” vs “disagreement”

The discussion summary for that observation is basically

  • side A: Fully conservative on insufficient evidence - on claims as future conspecific cryptics overlap in same morphospace and lack of enough sample set from purely holotypes to argue on morphometrics, burden of proof is fully on species IDer upon lacking these, explicit disagree to genus ID.
  • side B: Best evidence - All described existing holotypes of genus occupy distinct multivariate morphospace in current knowledge, burden of proof is shared if explicitly disagreeing species IDs under this case of current literature, absolute certainty is impossible in lot more IDs always in science.
  • Side C: other ID etiquette? - share details in comments
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I’d like to respectfully suggest that if you edit some of your text you are likely to get more people engaging on your question. I know the technical words you are using and in many cases simpler words would be not only clearer but also more correct. Morphometrics, for example, is a particular set of research methods, not just a fancier way of saying morphology.

I think what you are trying to ask is, “How do you approach observations where some IDers say the evidence is lacking on key traits but others say there is no other species it could be?”

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This is something I have thought about a lot, and I think it depends in part what taxa one works with. I guess if I had to describe my approach, I’d call it “flexibly conservative”, but closer to side B. When I started out, I thought ID should be based on a set of definitive binary features that eliminated all other possibilities, but quickly realized that was unrealistic. I ID morels, and most of the species are semi-cryptic: there is often high morphological variability with overlap between the species (overlapping bell curves for each trait).

At the same time, many semi-cryptic species look extremely distinctive a large fraction of the time, and for those individuals that are, I am highly confident in the species ID (these are the only ones I ID to species). The same thing can happen for morphologically cryptic species with partially overlapping habitat or seasonality. But then there will be observations that occur in the overlapping portion of the range, season, or morphological continuum, and I leave those observations at a higher taxon.

This is unavoidably subjective, as there is no sharp cutoff for qualitative traits occurring on a continuous spectrum, and in reality, I’m often considering several different variable traits/factors together. When done properly, I think this can be quite rigorous (if you are cautious and know your limits). For these more subjective IDs with high variability, I think one needs a “ground truth” dataset to both train themselves and test themselves on. For the species I ID, I look through every observation with DNA sequencing, and I try to naiively ID it myself (ignoring the sequence and the community ID). Without doing this, you have no idea how good or bad your ID ability actually is.

I have no problem explicitly disagreeing with an ID when I believe there is insufficient evidence, and I do this with high frequency given the abundance of unsupported over-precise IDs for fungi. At the same time, I don’t blindly adhere to keys, publications, or even my own personal criteria (which combines things from multiple sources and personal experience). If someone can provide evidence that species can be distinguished using an alternative set of characteristics I had not considered, I will evaluate the strength of their evidence/arguments. If it feels like it’s simply a pretext for guessing with no rational basis, I may persist in disagreeing. If it’s plausible but I’m unsure, I’ll refrain from challenging it or withdraw my disagreement. If I find it to be reasonable and reliable, I may incorporate it into my own ID practices.

I think dialog and willingness to reconsider is the most important part. Someone is unlikely to be a good identifier if they rigidly insist that ID must be done using only their criteria/sources (i.e. “you can’t possibly ID that with ‘trait X’ because it’s not in the key” or “you can’t possibly ID that without ‘trait Y’ because it is in the key”). The same is true of someone who only follows their own personal system (not supported by any keys/sources), can’t explain how they make their IDs, can’t reasonably defend them, and won’t change their approach when presented with evidence of its unreliability. Yet disagreement is central to how iNaturalist works, and if the community can’t agree on the ID, that is accurately reflected in the absence of a species-level community ID, leaving only the strongest and most uncontested IDs at research grade (in theory…).

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Thanks I have edited the title

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I have been annotating dingo tracks this week and the question comes up how one can differentiate between dingo and feral dogs for an ID when all you have is a footprint. There is increasing research that many wild dogs are actually dingo or very close to purebred particularly in the Far North or the more rural areas of the Outback. Location potentially is a thing - one observation is in the middle of Outback WA with nearby towns largely being a FIFO workforce i.e. no pets. Lots of dingo observations in the area. I feel reasonably confident that a canid footprint there is a dingo. I would not say the same in many other places.

The technology to differentiate between different types of footprint does exist but no one has used it for dingo research yet.

I’m sure that the local Indigenous mob have enough tracking expertise to tell the difference too but unfortunately I don’t know if any are on iNat.

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Honestly, it really depends on the group we’re trying to identify. I regularly monitor Collembola (springtails), and in that world you have to be extremely cautious even when something looks only slightly different. There are dozens upon dozens of undescribed species—some of them very common—and what we think of as a single “common species” often turns out to be several cryptic ones. North American Collembola are especially understudied, and we’ve only just begun to understand the real diversity.

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You could list the other species it could be and ask them to justify why it can’t be, based on the evidence provided or evidence generally accepted (e.g. in the generally accepted category: species X is not known from this country).

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