Create a new taxon rank for iNaturalist: the species group

the species group
Large genera can often become unwieldy, necessitating infrageneric ranks. In many cases authors wish to group similar species together for identification purposes, but do not want to give the group a formal name such as required for subgenera or sections. The species group fills this role, and has been used quite extensively in many speciose genera across disparate taxa. However, iNaturalist does not currently have a rank for this concept, and I thus propose that the taxon rank “species group” be added to the iNaturalist taxonomy. This feature request is born out of the discussion here: https://forum.inaturalist.org/t/large-genera-with-formal-species-groups/11073

example
The genus Efferia (Insecta: Diptera: Asilidae; https://www.inaturalist.org/taxa/61610-Efferia) is a large genus with nearly 200 known species and many undescribed. Hine (1919) proposed 8 species groups and these are frequently used by the community (e.g. https://bugguide.net/node/view/5188/tree). Efferia is the most observed genus of robber flies on iNaturalist (>8,000), and yet most observations are left at genus (~69%!) due to the large volume of similar species. However, using the species group rank (in the style of BugGuide) would allow for the more manageable sorting and identification of this genus. This principle applies equally well to many other genera that have existing named species groups.

An equivalent rank does not exist on iNat
There are currently five taxonomic ranks on iNaturalist between genus and species, and none of them are a proper substitute for species groups: genushybrid, subgenus, section, subsection, and complex. The first rank obviously is only relevant for hybridization events. Subgeneric names are governed by the codes of nomenclature, and while applying to similar concepts as “species-groups,” are not equivalent for this reason. Section and subsection are likewise formal taxa, although applying only to organisms covered by the ICBN (e.g. plants and fungi) and should not be used for animals. Finally there is the species complex, another informal rank that is best applied to closely related species that can be difficult to separate. Species groups are broader groupings of species and are not directly equivalent to the more narrow concept of complexes. Indeed, it is possible to have species complexes within species groups.

The terms formal and informal can have different meanings depending on context. Here I use the term “formal” to refer to ranks covered by codes of nomenclature such as the ICZN or ICBN, whereas “informal” ranks are not. While species groups are “informal” in this sense, they are often still rigorously defined in the literature.

implementation on iNaturalist
The rank of species group is perhaps best suited between subsection and complex. iNat staff evidently prefer ranks that consist of a single word without hyphens, so I propose “speciesgroup” or simply “group” for this rank. There has been discussion on how complexes are displayed on iNat (https://www.inaturalist.org/flags/331324), and while maybe not ideal, for the sake of standardization species groups can use a similar format: e.g. Group Efferia albibarbis. The curator guidelines for species groups would be essentially the same as for complexes (https://www.inaturalist.org/pages/curator+guide#complexes).

@treichard @nomolosx

I’ll add a quote here of the example I mentioned in the original thread:

It would be fantastic to have this change. curators are very resourceful people that do the best they/we can with what they’ve got, but this can result in some erroneous taxonomy if there are incomplete taxonomic features. adding this feature would greatly flesh out the taxonomy of the site and could really help revamp my area of curation.

I second everything @Myelaphus has to say about this.

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The species group rank is needed for insects, just as kingdoms other than Animalia need the additional rank between subgenus and complex to handle large genera.

@Myelaphus Thanks for writing this feature request.

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I’m not endorsing the idea of a species group rank. But one thing to keep in mind that on iNat ranks need to have levels as well. e.g. here are the ranks including and between genus and species:
genus
subgenus
section
subsection
complex
species
So its important for any proposal to include the level of this rank (e.g. where it would insert in this list)

If this is an insect only problem, my preference would be to coerce ‘section’ and ‘subsection’ which is restricted to plants into this use case rather than add entirely new ranks

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I think that information was already buried in the request:

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As long as the use of species groups is restricted to animals (not sure whether that’s the case or not), this seems like a reasonable implementation to me, as long as it can be made to appear differently depending on taxonomic context. “Section” and “Subsection” already exist elsewhere in the ICZN system (between Infraorder and Superfamily, on iNat as “Zoosection”/“Zoosubsection”).

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Here is an example of a species complex: https://www.inaturalist.org/taxa/1076089-Abraxas-amicula-illuminata (is species complex the same thing as species group?)

Edit: OK appraently they are not

This is a problem I had not considered, and IMO is another good reason why using the botanical section and subsection in animals as a substitute for species groups is a bad idea. It only further confuses the distinction between how the terms are applied in zoology and botany. No thanks.

Numerous other organisms use species groups, e.g.:
Nematodes: https://en.wikipedia.org/wiki/Caenorhabditis
Reptiles: https://academic.oup.com/sysbio/article/63/2/119/1642608
Fungi: https://www.tandfonline.com/doi/abs/10.3852/12-249
Plants: https://bioone.org/journals/Weed-Science/volume-51/issue-5/P2002-IR/The-foxtail-Setaria-species-group/10.1614/P2002-IR.full

That species groups are used in botany pretty much destroys any argument that the botanical section/subsection is a valid substitute for the species group rank.

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To be fair, it was not ‘buried’ in the request. It was the first sentence under “implementation on iNaturalist,” the most sensible place for it to be IMO.

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Fair enough, poor word choice on my part.

Interested to hear if this request is still under consideration.
I understand the desire too keep the number of taxon levels to a reasonable limit, however it feels weird to offer a bunch of options for plant taxonomy and less so for animals - it has been demonstrated the ‘species group’ is used across the animal kingdom for large genera. As the ‘section’ term cannot be used as a replacement, it would be great to get at least this one addition below the genus rank.

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I would agree with everything that’s been said, this should go between subsection and complex. This is a fairly common rank (much more so than complex or subsection in groups I’m familiar with) and would be quite helpful.

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Yeah, I would like to see this as well.

There are even some groups in Pentatomidae that aren’t necessarily explicitly recognized as “species groups” by the experts that I would be interested in discussing some sort of option like this for.

Having a hard time phrasing this well, so let me try to explain: One example is a pair of similar-looking Euschistus (crenator and quadrator) that can’t really be told apart from photos- need to examine genitalia, I believe. They look pretty distinctive compared to other species, so it seems a shame to leave them all the way up to genus level.

There are also a pair of Chlorochroa that require genital examination. C. lineata and C. faceta are supposed to be impossible to differentiate reliably from photos. They’re quite distinctive from other members of the genus though. Could we group those two together?

I think in those cases the species complex would be more appropriate - i.e. very closely related species that are difficult or impossible to separate from photos. The species group is intended to be more broad, closer in concept to subgenera.

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Gotcha.

Would LOVE this! It would be so useful - for example, for implementing Habronattus species groups, which are here: https://bugguide.net/node/view/6776/tree

So, if I understand correctly, this could be used as a way to divvy up a genus in a way that gives a more specific identification to a subset of species which can be grouped together somehow. To paraphrase, you intend for these simply pragmatic, functional groupings which likely do not have a formal basis in literature, but which would be useful for computer vision and users when the next level above species is an excessively large genus. Is that right?


Thanks to @carnifex for the clarification. I’m a bit more familiar with plants, so that makes sense.

I was confused, given that Wikipedia’s entry for Species complex, to which “species group” points, describes “species group” as informal:

“As informal taxonomic ranks, species group , species aggregate , and superspecies are also in use.”

As well as several other items I’d previously read which that talk about “species groups” in a very informal sense as being practical, informal, or temporary when molecular phylogeny awaits.

No, that is not accurate. The species-group is a valid taxonomical rank and used in phylogenetic studies, as is the case for the section with plants

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They are informal in the sense that they are not governed by rules of nomenclature (e.g. ICZN, ICBN), but they are often precisely defined and used in the literature.

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Groups and complexes are not valid ranks, they’re a convenience used in taxonomic discussion, and they’re largely synonymous concepts. I’ve never seen much of a distinction between a group vs a complex, unless one wishes to define the latter based on allopatry (which is by no means universally accepted). I agree with the need for grouping taxa in this non-Linnaean manner, but I’m opposed to creating a bunch of needless and poorly defined ranks. I don’t know how botany handles this (apparently something about sections and subsections), but there should be a single informal rank to handle these supraspecific clades.