recognize nothgenus xCystocarpium (Cystopteris x Gymnocarpium) [PASSED]

[crothfels]

Name of taxon

xCystocarpium

Rank of taxon

Nothogenus

Approximate number of species affected

1

Description of change

This proposal is to recognize the nothogenus, xCystocarpium, between the genera Cystopteris and Gymnocarpium. xCystocarpium contains a single recognized species, xCystocarpium roskamianum Fraser-Jenk.

Reason for change

Notho taxa were not recognized in PPG I, but we're planning on including them in PPG II, so a proposal is necessary. The two parental genera (Cystopteris and Gymnocarpium) were each recognized in PPG I and I'm not aware of any suggestion to consider lumping them together (historically they were often thought to be in different families from each other). The parentage of the xCystocarpium roskamianum was initially hypothesized based on morphological data (Fraser-Jenkins 2008) and has been confirmed with low-copy nuclear data: one parent is G.dryopteris and the other is a Eurasian member of the C.fragilis complex (Rothfels et al. 2015). xCystocarpium roskamianum is a robust plant, but is sterile, presumably due to meiotic difficulties: it is a recently formed allotetraploid of two other allotetraploids (so has four distinct subgenomes), and the parental genera themselves are inferred to have diverged from each other ~60 million years ago.

Christopher Fraser-Jenkins. 2008. Taxonomic revision of three hundred Indian subcontinental pteridophytes with a revised census-list: A new picture of fern-taxonomy and nomenclature in the Indian subcontinent. Bishen Singh Mahendra Pal Singh, Dehra Dun, India.

Carl J. Rothfels, Anne K. Johnson, Peter H. Hovenkamp, David L. Swofford, Harry C. Roskam, Christopher R. Fraser-Jenkins, Michael D. Windham, and Kathleen M. Pryer. 2015. Natural Hybridization between Genera That Diverged from Each Other Approximately 60 Million Years Ago. American Naturalist 185:3, 433-442. https://www.journals.uchicago.edu/doi/abs/10.1086/679662

Rothfels et al.AmerNat.2015.pdf

Reference(s) for publication of the name

Christopher Fraser-Jenkins. 2008. Taxonomic revision of three hundred Indian subcontinental pteridophytes with a revised census-list: A new picture of fern-taxonomy and nomenclature in the Indian subcontinent. Bishen Singh Mahendra Pal Singh, Dehra Dun, India.

Fraser-Jenkins, C. R., Y. P. S. Pangtey, and S. P. Kullar. 2010. Asplenium laciniatum D. Don (Aspleniaceae), a critical complex, and confused species in the Indian subcontinent. Indian Fern Journal 27:212–214. (This publication makes the orthographic correction of "roskumianum" to "roskamianum".)

Fraser-Jenkins_2010_Indian_Fern_Journal.pdf

List the numbers of any related issues

No response

Code of Conduct

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

[msbarkerAZ]

I support this proposal. Good evidence for this intergeneric hybrid and no good reason to combine these genera.

[joelnitta]

This proposal was voted on during PPG Ballot 1 (voting period July 2023). A total of 63 votes were cast. There were 60 'Yes' votes (95.2%) and 3 'No' votes (4.8%). The proposal passes.

[joelnitta]

Already implemented in data, closing.