Insect species complexes: to create in iNat or not to create?

INaturalist has 5 requirements to create a species complex: https://www.inaturalist.org/pages/curator+guide#complexes
I think all 5 of these are essential, but I’m curious how literally to interpret “Complex is recognized in the literature”.

I argue below that closely related insect species, in the literature suggested to be monophyletic and separated only by male genitalia, should be represented as identifiable units in the iNat taxonomy when further ID is impossible. Overly narrow interpretations of the requirement that a species “complex” is explicitly erected in the literature may hurt iNaturalist users, and I don’t see their purpose. Below, I discuss the case of North American Rivellia as an example of a widespread question.

The vast majority of the Rivellia from North America belong to the pallida/imitabilis or colei/quadrifasciata groups, which cannot be identified further photographically; females cannot be identified without DNA. Namba (1956) suggests the monophyly of these two species groups, although this was before scientists conceived of “monophyly” as an explicit term.

This species group has no name in the historical literature: why would taxonomic experts erect a “species complex” for a group of only 2 species? Just label the females “Rivellia pallida or imitabilis,” give them their own tray in the collection, and report them as such! Only with three or more species would a “species group” formal designation serve a purpose. Thus, a well-recognized species group could exist in every museum collection for hundreds of years but never be formally recognized in the literature.

According to the current iNat taxonomy, observations of these Rivellia flies must be left at genus. Yet this creates a big problem for someone trying to get a sense for the species found in their area. The two groups Rivellia colei/quadrifasciata and Rivellia pallida/imitabilis cannot be identified further and form the vast majority of Rivellia observed in North America, but are completely unrepresented in an observation search (or thus by the AI): https://www.inaturalist.org/observations?place_id=1&subview=grid&taxon_id=132237&view=species

I don’t think every set of similar species should get its own place in the iNat taxonomy. However, it seems reasonable that two cryptic sister species should be recognized, even if historical literature never bothered to specifically use the words “group” or “complex” to describe them. These terms are only slowly starting to appear in entomology, and many branches of insect taxonomy haven’t been touched by experts in a century.

Since I’ve done the research, I’d like to create Rivellia pallida/imitabilis and colei/quadrifasciata as ‘complexes’ in the iNaturalist taxonomy. Does anyone object or agree?

Thanks for your feedback!

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Create! And I think that here also may be used “s.l.” (sensu lato) after the species name.

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As a layperson, I always appreciate the extra layer of detail that having a species complex can provide.

It might also help prevent bad data from being created, by people unaware of a DNA requirement for separation for instance?

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Not an entomologist, but I think you lay out a good case for why including a species complex for this example is valuable.

The only potential downside I can see is if adding a “species complex” might introduce some confusion, potentially because other users who aren’t as familiar with the taxonomy might not be able to look it up online (as you say it hasn’t been called a complex in the literature). I’m not sure if that is a reasonable concern or not, or even if it is, the benefits might still outweigh that!

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In short - do it! I had similar situation with lichens. People accept complexes much better that genus level IDs. And this results in better quality of data, too.

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This has always puzzled me. I identify Noctuidae, and two very common moths are Xestia c-nigrum & Xestia dolosa. In Bugguide (which is the taxonomic structure that iNat follows for insects) it says that east of Manitoba the two cannot be distinguished visually - https://bugguide.net/node/view/30522 . Xestia c-nigrum is found in Europe as well. I’m not a taxonomist, but this suggests to me that Xestia c-nigrum is either replacing Xestia dolosa.or they are are so similar that the two species may mix. Or the pheromones prevent mating.
It would be nice to have some clarity on instances like this - as it is, I’m not sure what to do.

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I assume the goal of requiring complexes to be recognized in the literature is to prevent abuse and unnecessary proliferation of complexes on iNat (especially since iNat records are ported to GBIF). However, I think it’s justifiable to create a complex that that does not meet this criterion if the other criteria are met, and if doing so substantially improves identification.

Hopefully someone more familiar with the formulation of these curator guidelines can chime in.

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I don’t know anything about this particular case, but it is also possible that the opposite is true, that they are in the start of (at least in evolutionary time scales) diverging into separate species from a single source.

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Why could GBIF create a problem? If an observation were marked as Rivellia pallida complex on iNat and there’s no corresponding complex in GBIF, wouldn’t it just import as Rivellia? Curious to learn more.

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It looks like GBIF currently doesn’t know what to do with complexes and simply maps the observation to the species that’s named in the complex name string, e.g.: https://www.gbif.org/occurrence/2005406919

That’s a problem because it creates spurious species records.

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Oops. I let them know: https://github.com/gbif/portal-feedback/issues/2935

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That’s a problem! But that’s going to happen even with completely accepted species complexes. Is there a fix? Maybe don’t use the species name for the complex??

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Thanks! (Do we say that in the forum?)

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Yes! :-)

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I wonder if we can bring this to further generality. There are many cases in which, given a list of possible species A,B,C,D,E, we can say “it’s either A or D but we cannot say more”. Sometimes because they are not distinguishable visually at all, as discussed in this thread; sometimes because the picture(s) do not allow it. Which is different from being able to identify only at genus level. It’d be nice therefore to have a mechanism where we can identify as multiple possible species (genera, families etc.) when we can narrow to a subset.

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Again, I have found the same thing with moths. There are two species in the Genus Feltia which are very difficult to tell apart, mainly because of individual variability. Setae on the antennae are the best way, but these can only be seen if the picture is just right. When I identify them, I generally can only go to genus, and suggest the observation might be this, or that. It gets to be time consuming, as they are common moths.

eBird does this with “slashes”, for example Willow/Alder Flycatcher, Downy/Hairy Woodpecker. But the two most similar species aren’t always the two most closely related species (i.e. not monophyletic). More discussion here: https://forum.inaturalist.org/t/ability-to-id-to-a-group-of-visually-similar-species-within-a-genus/5655

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FWIW, I agree and think we need more of them. An example is the Desmia funeralis/maculalis group. They can be ID’d to species if all of the characters are found in photos, but they rarely are visible. Therefore we have a “complex” and a place for the individual species when it is known (has been dissected or better photos taken). We need to create an Olethreutes furfurana group if anyone is reading that is familiar with doing that. There are probably multiple species there and after dissection I now leave many of them at Genus level because of that.

Are these groups monophyletic? At the end of the day, official iNat taxa can only be created for monophyletic groups. (except for higher taxa like Reptilia which have their own set of rules somehow)

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We are waiting for an answer for whether formal species groups will be added as a separate rank.
https://forum.inaturalist.org/t/create-a-new-taxon-rank-for-inaturalist-the-species-group/14543
Knowing the answer to that question would help figure how to approach certain complexes.

Sometimes the monophyly check for a potential few-species complex isn’t very conclusive, but the complex is inside a formal species group, which is described to be likely monophyletic. Without the group rank, if the species group is added at the complex rank, then probably all groups in the genus or subgenus should also be added, leaving no rank for further complexes within sister groups. If species groups could be added at their own rank, then some of the potential complexes are not so necessary, and those that remain necessary still have a rank available for them.

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