Generic division in the lycophytes
Vascular plant curators here are probably already aware that there's a significant variance between the classification for ferns adopted by POWO, and PPG I; the latter (in my opinion, anyway) has more support among the pteridological community and we've adopted it as our classification scheme. (Hopefully this summer I'll have time to get back to adding deviations to harmonize the two.)
However, a similar problem exists with regards to lycophytes, specifically family Lycopodiaceae. Older systems treat this family as monogeneric, containing only genus Lycopodium. More recently, the deeper divisions in the family have been recognized and Lycopodium sensu latissimo has been split up; the question is, how much to do so.
PPG I recognizes 16 genera in Lycopodiaceae, divided among three subfamilies: the Huperzioideae, Lycopodielloideae, and Lycopodioideae. By contrast, POWO treats each of those subfamilies as the broadly circumscribed genera Huperzia, Lycopodiella, and Lycopodium, respectively.
Our existing taxonomy, owing in part to its roots in Flora Novae-Angliae, generally inclines towards the "splittier" approach taken by PPG I. My personal sense of taxonomic trends is that the degree of splitting in PPG I, which was pretty forward when Haines wrote it into Flora Novae-Angliae, has now become pretty widely accepted and that we should adopt PPG I for lycophytes as well as ferns.
The main impact would probably be in the tropics, where Pseudolycopodiella and Palhinhaea would get split from Lycopodiella, a bunch of Huperzia would get moved over to Phlegmariurus (which is active in our taxonomy, but many species have not been moved). The Palhinhaea split would probably be the most visible, as Palhinhaea/Lycopodiella cernua is an extremely common pan-tropical clubmoss.
I'd like to know if other curators are on board with this approach; @crothfels who has brought up some of the inconsistencies in our current taxonomy.
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I'd prefer to stick with the broadly circumscribed Huperzia, Lycopodiella, and Lycopodium.
PPG I split quite a few genera with apparently no good reason other than they could.
I've ranted about this elsewhere: https://blog.tepapa.govt.nz/2018/08/31/why-do-scientific-names-change-kiokio-by-any-other-name/
Understood. Would you be OK with splitting out Phlegmariurus (and Phylloglossum) from Huperzia? That's consistent with the current position of Flora of New Zealand, allows recognition of the distinctness of Phylloglossum, and still leaves Huperzia fairly speciose, with a nice synapomorphy in the form of gemmae and gemmiphores. I'm not at all familiar with the Southern Hemisphere proposed segregates from Lycopodium, so am not particularly inclined to disturb them in the face of objection.
I do share in principle your general concerns about oversplitting in some areas of PPG I--I'm planning to leave your New Zealand trichomanoids in Trichomanes whenever I get to sorting out the POWO-driven moves in the filmies. Are there any plans to reconvene PPG in conjunction with the Sao Paulo meeting next year? If I'm reading the subtext correctly, the pressures which led to PPG I being issued originally have somewhat abated, so it seems like a good time to revisit some of the generic-level decisions, although Thelypteridaceae and Tectariaceae, for instance, don't seem ripe yet.
Thanks @choess. I support splitting Phlegmariurus and Phylloglossum from Huperzia; that's actually the situation we already have on iNaturalist in Australasia.
I'm not sure what is happening with PPG - I'm a bit out-of-the-loop with regard to PPG and POWO.
I don't think there's a formal PPG revision planned in the near future (although we are working in the direction, or at least in parallel, through our efforts on the taxonomic thesaurus for the Pteridophyte Collections Consortium portal (pteridoportal.org)). Personally, I would advocate for the PPG treatment for lycophytes; the broader Lycopodium s.lat. and s.lattissimo treatments are horrendously lumpy, in my opinion; I see little value in keeping heterogenous groups together just because they look similar to many people's eyes, and at some point in the past we didn't know enough about their relationships to strongly support alternative treatments. But we do now! For example, the stem ages of most of the "splitty" genera are comparable to, or older, than the stem age of Asteraceae (I'd have to do more digging to be more precise, but I think this is the general picture). For other arguments the PPG classification, interested readers might consider reading the supporting literature (cited in the PPG publication), and Schuettpelz et al. 2018 "Are there too many fern genera?", Taxon.
@westontesto @scheuchzeria
@leonperrie -- I read your article (that you mention earlier in this thread), fyi, and agree with you in most respects--you make a good argument. I think the only difference of opinion I have is in the relative weighting of criteria (stability vs. evolutionary distinctiveness, diagnosability, etc).
Since this is coming up again in some of the stalled swaps, my take on some possible approaches that have come up (for Lycopodioideae and Lycopodielloideae, sensu PPG I, we seem to have consensus on Huperzioideae):
1) Adopt POWO/NZ Flora circumscription of each of these as a single genus, Lycopodium and Lycopodiella. Pro: no need for taxon deviations, compatible with NZ usage and historical usage worldwide. Con: not compatible with current North American usage and floras or PPG I, probably not compatible with current expansion of alpha taxonomy (1 taxon in Spinulum and 2 taxa in Diphasiastrum have no species-level combination in Lycopodium, 6 taxa in Palhinhaea, 4 taxa in Pseudolycopodiella and 1 taxon in Lateristachys have no species-level combination in Lycopodiella.), probably not liked by lycophyte specialists.
2) Adopt PPG I splitty circumscription of these subfamilies. Pro: compatible with US floras, probably preferred by lycophyte specialists and compatible with any new species in the near future. Combinations exist for all taxa. Con: need to install taxon deviations to POWO, incompatible with NZ usage and perhaps a certain amount of current usage in the tropics (I'm thinking Lycopodiella/Palhinhaea cernua).
3) "split-the-baby": keep mostly northern-hemisphere genera (Diphasiastrum, Dendrolycopodium, Spinulum) split from Lycopodium, lump mostly Asian/southern hemisphere genera (Austrolycopodium, Diphasium, Pseudodiphasium, Pseudolycopodium, Lycopodiastrum) in Lycopodium. Lump Lateristachys in Lycopodiella, maybe also Pseudolycopodiella and/or Palhinhaea. Pro: most taxa and observations stay at name used in regional flora (US and NZ). Some deviations needed. Con: Some deviations from POWO needed; still problems with alpha-taxonomy in an expanded Lycopodiella and probably not liked by the lycophyte specialists, especially there.
My initial reaction is that option 3 makes me nervous. Unlike options 1 and 2, it results in a weird mixed of monophyletic (the recognized "split" genera like Diphasiastrum) and non-monophyletic (Lycopodium, Lycopodiella) genera. I would be happier with options 1 and 2 coexisting, if that's possible (people in one area of the word could use one, and people in another area of the world the other?), than I am with option 3. Of course, I think that option 2 is heads-and-shoulders the best representation of the evolution, and thus "nature", of these entities ;-) @westontesto @lycophyte @scheuchzeria
If I understand it, option 3 allows users in different parts of the world to continue using the scheme they're familiar with. I reckon the benefits of that may outweigh the messiness it creates for taxonomists (who, in any case, have the skills to deal with it).
I suspect iNaturalist can't (currently) have 1 and 2 coexisting, but it would be great if we could, and I'm looking forward to iNaturalist implementing the ability to have different/conflicting taxonomic schemes in different parts of the world, similarly to how it already deals with regional variation in common names.
Any thoughts on generic circumscription in Lycopodiaceae? @jasonrgrant @barbaraparris @david_lyttle @gzuquim @gabriel_moulatlet @mftasp @galanhsnu @danaleeling
While I agree that 3 has problems, I think it would be my preferred choice, among other things because being closer to local usage, it will give the least disruption to users.
I think that we should follow PPG I entirely for Lycopodiaceae, and make all the nomenclatural changes here on iNaturalist.
There is an increasing number of both molecular phylogenies and regional treatments that support PPGI, see for example the recent paper by Ashley Raymond Field "Classification and typification of Australian lycophytes and ferns based on Pteridophyte Phylogeny Group classification PPG I". Australian Systematic Botany, 2020, 33, 1–102. https://doi.org/10.1071/SB18011. "The classification and typification of all Australian ferns and lycophytes is updated to reflect the Pteridophyte Phylogeny Group I classification and the International Code of Nomenclature for algae, fungi, and plants, presenting 8 new nomenclatural combinations as well as 85 lectotypifications."
It shouldn't be surprising that Ashley's paper follows PPG for Lycopodiaceae since he was a member of the Lycopodiaceae sub-committee for PPG !
From a regional perspective, I'm interested to see what the Australian Plant Census does (https://www.anbg.gov.au/chah/apc/about-APC.html ). All of the state herbaria contribute to it, providing a 'consensus' decision on whether to adopt proposed changes.
My thanks to @crothfels for tagging me into this conversation, very much appreciated. I noted the activity at https://www.inaturalist.org/taxon_changes?taxon_id=67941. My role is only that of an instructor working with students, I do not have the background to weigh in on the taxonomy of Lycopodiopsida. I have noted that teaching students that Lycopodiella cernua is a lycopodium is perhaps easier than teaching them that Palhinhaea cernua is a lycopodium, but that is not a basis for retaining a taxonomic name. That said, I try to keep my students up to date with current thinking in taxonomy. I also saw that Huperzia phlegmaria is now Phlegmariurus phlegmaria in iNaturalist, a plant that is used here as a head garland for dancers only when dancing in their home land unit. I would note that having names that change according to the region/location on the planet feels complex. If I teach a student a name here in Micronesia, and then they travel to another region and the name changes for the same species, that will be confusing. Again, thanks for tagging me into this conversation.
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