While searching for the identity of Thelypteris motleyana that I shared last week, I noticed that the fern was classified under the family Aspleniaceae in the Plants of the World Online (POWO) website. I had thought that it should belong to the family Thelypteridaceae instead.

I wrote a note in 2015 on the confusion of the naming of the ferns in the family Thelypteridaceae back then. Soon after, 2 different camps emerged on the classification systems for the ferns which affected their accepted botanical names. In the past, I did not stick to a specific plant classification system for indicating the accepted botanical name of the plants in my website but reply on whatever I came across that make sense. Since the beginning of this year, I had started to update the accepted botanical names of the plants in my website to POWO website hosted by the Royal Botanic Gardens, Kew in UK. It is still work in progress.

While there was no major disagreement in the flowering plant classification, it was not the case for non-flowering plants (specifically ferns). The fern classification in the POWO website was based on the system proposed by Christenhusz [1-2] flavouring the least number of families and genera for the ferns. The other camp did not agree with this minimalist approach [3] and preferred to stick to the system proposed the Pteridophyte Phylogeny Group (PPG) [4] that assigned more families and genera. The popular iNaturalist website belonged to the PPG camp judging from the naming of ferns in their website. Overall, there seemed to be more supporters of the PPG system in view of the amount of recent publication referencing to this system [5-7].

Closer to home, the Flora of Singapore had decided to adopt the classification system proposed by PPG [8] and thereby ignore the one proposed by Christenhusz. I had decided to align the plant names in my website including ferns that used by the POWO website. While I understand the arguments from both camps, my preference will be to keep the system simple and hopefully, the experts will minimize frequent changes to the accepted botanical names (which will reduce the hassle for me to update the plant names in my website too often).

In conclusion, I had re-grouped the ferns that I placed under the family Thelypteridaceae previously to Aspleniaceae in accordance with the convention used by the POWO website. Thelypteridaceae is now considered a subfamily of Aspleniaceae. I had added an updated to the fern name comparison table in my previous 2015 note.

References:

[1] Christenhusz MJM, Fay MF, Byng JW. (eds.) GLOVAP Nomenclature part 1. The Global Flora, Special Edition 2018;4:1–155. | Read article |

[2] Christenhusz MJM, Chase MW. PPG recognises too many fern genera. Taxon 2018;67(3):481-487. | Read article |

[3] Schuettpelz E, Rouhan G, Pryer KM, Rothfels CJ, Prado J, Sundue MA, Windham MD, Moran RC, Smith AR. Are there too many fern genera? Taxon 2018;67(3):473-480. | Read article |

[4] The Pteridophyte Phylogeny Group. A community-derived classification for extant lycophytes and ferns. J Syst Evol 2016;54(6):563-603. | Read article |

[5] Nitta JH, Schuettpelz E, Ramírez-Barahona S, Iwasaki W. An open and continuously updated fern tree of life. Front Plant Sci 2022 Aug 24;13:909768. | Read article |

[6] Fawcett S, Smith AR. A Generic Classification of the Thelypteridaceae. Fort Worth: Botanical Research Institute of Texas Press. 2021. | Read article |

[7] Fawcett S, Smith AR, Sundue M, Burleigh J, Sessa E, Kuo L, Chen C, Testo W, Kessler M, GoFlag Consortium, Barrington D. A global phylogenomic study of the Thelypteridaceae. Syst Bot 2021;46(4):891-915. | Read article |

[8] Middleton DJ, Ho BS, Lindsay S. 2. Taxonomic overview of The plants of Singapore. Flora of Singapore 2019;1:5-14. | Read article |