Additionally recognizing the genus Microschizaea in the family Schizaeaceae. [PASSED]

[lykuofern]

Author(s) of proposal

Li-Yaung Kuo

Name of taxon

Microschizaea

Rank of taxon

Genus

Approximate number of species affected

7

Description of change

Additionally recognizing Microschizaea in the family Schizaeaceae.

Reason for change

(The type of) Microschizaea had not been phylogenetically sampled until Ke et al. 2022. This genus is found phylogenetically segregated from Schizaea s.s.. If recognizing Actinostachys as in PPG I, Microschizaea shall be treated as a different genus to make each of them monophyltic.

Reference(s) for publication of the name

Ke B-F, Wang G-J, Labiak PH, Rouhan G, GoFlag Consortium, Chen C-W, Shepherd L, Ohlsen DJ, Renner MAM, Karol KG, Li F-W, Kuo L-Y (2022). Systematics and plastome evolution in Schizaeaceae. Front. Plant Sci. 13, Article 885501.

Reed C. F. (1947). The phylogeny and ontogeny of the Pteropsida. I. Schizaeales. Bol. da Soc. Broteriana, ser. 2 21, 71–197.

List the numbers of any related issues

No response

Code of Conduct

• [X] I agree to follow the PPG Code of Conduct

[joelnitta]

Link to Ke et al (2022): https://www.frontiersin.org/articles/10.3389/fpls.2022.885501/full

[leonperrie]

There seems some merit in considering a broadly circumscribed Schizaea (i.e. including Actinostachys and Microschizaea).

I appreciate that Actinostachys is easy to recognise (at least the species I’m familiar with). But many botanists are going to find it challenging to distinguish the clades of Microschizaea and Schizaea sensu stricto in the field. At least some species from these two clades are regularly confused for one another.

With the assumption that Schizaea pusilla was part of the Microschizaea clade, it seemed that the phylogeny inferred by Wikstrom et al. (2002) could be converted into a simple binary generic classification where Actinostachys was easy to morphologically separate from the monophyletic remainder of Schizaea. I guess I was lulled by that at the time, and perhaps others were too. But it turns out that assumption was wrong, and the phylogeny is more complicated.

I know that it is possible to discern the three clades by close inspection of the morphology, but field botanists might not be appreciative. Subgenera or informal clade names could provide alternative means of signalling the relationships among species for those of us that want to.

[lykuofern]

Hi Leon and all,

Happy to hear more discussions here! Personally, to divide the four clades, the generic system with either one, three, or even four genera is fine for me. I would like to provide some notes here:

(1) In the three genus system by Ke et al. (2022), Schizaea spp. differs from Microschizaea spp. in having hairs in their sori. The spores of Schizaea spp. are bilateral (P:E is 0.57–0.66). In comparison, the spores of Microschizaea are subglobose to ovoid (P:E is 0.74–0.76). Like Microschizaea., two Schizaea spp., S. pusilla and S. pectinata, also have simple undivided blade. Thus, features from their fertile tissues are most important ones to morphologically distinguish the two genera. More details in Table 1 of Ke et al. (2022)

(2) These four different clades are estimated being diverged 100-120 mya based on FTOL 1.5.

(3) When using the one genus system (i.e. Schizaea), new name combinations are needed to do for at least three species. No name combination has to do for the three-genus system at this moment. For the four-genus system, we need a new genus for S. pusilla.

(4) There are fossil taxa reviewed in Reed (1947), which proffers the three-genus system.

[choess]

I don't suppose you have a copy of Reed that could be attached? I was examining this, and IIRC he includes S. pusilla in Microschizaea, so a slight recircumscription of the latter would be necessary to reconcile it with the recent phylogeny. It looks from the table as though it requires sporangial and spore characters to separate the two?

[lykuofern]

I am happy to share the link of Reed (1947) here. Yes, sporangial and spore characters are most reliable ones to separate Schizaea and Microschizaea.

[crothfels]

oof. this seems tricky! If I'm understanding the Ke et al. phylogeny correctly, there isn't strong support for the relationships among the four main clades (it's possible that Schizaea s.lat and Actinostachys are reciprocally monophyletic, for example), even under inferences using full plastomes? But there is strong evidence that the four clades (Schizaea s.str., Actinostachys, Schizaea pusilla, Microschizaea) are each monophyletic and are each highly divergent from each other. So the most conservative approach (in the sense of being the least likely to require future changes) would be to recognize each of the four as its own genus. To me, the three-genus system doesn't feel great because it both requires changes from PPG I while also not being well supported (ie, it's quite plausible that Schizaea in the the three-genus system isn't monophyletic). The four-genus system also has the advantage (in my opinion) of better reflecting the evolutionary processes in the group--ie, how deeply divergent the major clades are. However, just to talk myself in a circle, I agree with @leonperrie that this would be a pain for field botanists (at least in some cases) and also that divergence times are highly uncertain in the Schizaeales.

[joelnitta]

This proposal was voted on during PPG Ballot 8 (voting period February 2024). A total of 65 votes were cast. There were 45 'Yes' votes (69.2%) and 20 'No' votes (30.8%). The proposal passes.