Abstract

We report the presence of Ceratopteris thalictroides based on a recent collection from northeastern Peru. This aquatic fern is widely distributed in the tropics, however, its presence in Peru remained uncertain and without a voucher until now. This finding increases to four the number of species of the subfamily Parkerioideae, Pteridaceae within Peru.

Keywords:
Ceratopteris; Pteridaceae; Peru; new record; pteridoflora

Ceratopteris is a monophyletic genus of the subfamily Parkerioideae (PPG I, 2016PPG I. 2016 A community-derived classification for extant lycophytes and ferns. Journal of Systematics and Evolution 54: 563-603. doi: 10.1111/jse.12229.
https://doi.org/10.1111/jse.12229.... ) that together with its sister genus Acrostichum include the only aquatic and semiaquatic members of the Pteridaceae (Schuettpelz et al., 2007Schuettpelz E., Schneider H., Huiet L., Windham M.D., Pryer K.M. 2007. A molecular phylogeny of the fern family Pteridaceae: Assessing overall relationships and the affinities of previously unsampled genera. Molecular Phylogenetics and Evolution 44: 1172-1185. doi:10.1016/j.ympev.2007.04.011.
https://doi.org/10.1016/j.ympev.2007.04.... ). Both homosporous genera are present in Peru (Tryon & Stolze, 1989Tryon RM, Stolze RG. 1989. Pteridophyta of Peru Part II. 13. Pteridaceae-15. Dennstaedtiaceae. Fieldiana Botany New Series 22: 1-128.), although the number of Ceratopteris species has remained inconclusive. Indeed, only New World C. pteridoides (Hook.) Hieron. is definitely known with vouchers from lowland Amazonian Peru (Tryon & Stolze, 1989Tryon RM, Stolze RG. 1989. Pteridophyta of Peru Part II. 13. Pteridaceae-15. Dennstaedtiaceae. Fieldiana Botany New Series 22: 1-128.; León, 1993León B. 1993. Los helechos acuáticos del Perú. In: Kahn F., León B., Young K.R. (eds.). Las plantas vasculares en las aguas continentales del Perú. Lima, IFEA. p. 129-152.); while C. thalictroides (L.) Brongn. has only been mentioned as expected (Tryon & Stolze, 1989Tryon RM, Stolze RG. 1989. Pteridophyta of Peru Part II. 13. Pteridaceae-15. Dennstaedtiaceae. Fieldiana Botany New Series 22: 1-128.) or ambiguously included (León et al., 2012León B, Huaman E, Roque J, La-Torre M, Cano A. 2012. Los helechos ornamentales en el Perú. Lima, Punto & Grafia S.A.C.). Ceratopteris thalictroides is a tetraploid (2n=77), widely distributed pantropical species known in tropical South America from neighboring Brazil (Hirai & Prado, 2020Hirai RY, Prado J. 2020. Ceratopteris in Flora do Brasil 2020. https://floradobrasil2020.jbrj.gov.br/FB91880/. 04 Sept. 2023.
https://floradobrasil2020.jbrj.gov.br/FB... ) and Colombia (Murillo et al., 2016Murillo PMT, Murillo AJ, León PA. 2016. Pteridofitos (Helechos y afines) In: Bernal R., Gradstein S.R., Celis M. (eds.). Catálogo de plantas y líquenes de Colombia. Bogotá , Instituto de Ciencias Naturales, Universidad Nacional de Colombia. p. 446-578. ) growing in aquatic environments below 500 m elevation. The available taxonomic revision of the genus (Lloyd, 1974Lloyd RM. 1974. Systematics of the genus Ceratopteris Brongn. (Parkeriaceae) II. Taxonomy. Brittonia 26: 139-160.) indicated a wide variability in sterile frond morphology for C. thalictroides, while later Masuyama et al. (2002Masuyama S, Yatabe Y, Murakami N, Watano Y. 2002. Cryptic species in the fern Ceratopteris thalictroides (L.) Brongn. (Parkeriaceae). I. Molecular analyses and crossing tests. Journal of Plant Research 115: 87-97. ) examined this morphological polymorphism among Japanese populations using molecular data that revealed three potential cryptic species, and with probable independent origins (Adjie et al., 2007Adjie B, Masuyama S, Ishikawa H, Watano Y. 2007. Independent origins of tetraploid cryptic species in the fern Ceratopteris thalictroides. Journal of Plant Research 120: 129-138. doi: 10.1007/s10265-006-0032-5.
https://doi.org/10.1007/s10265-006-0032-... ). Indeed, C. thalictroides represents an interesting species complex for further research in understanding reticulation and speciation as shown by Kinosian et al. (2020aKinosian SP, Pearse WD, Wolf PG. 2020a. Cryptic diversity in the model fern genus Ceratopteris (Pteridaceae). Molecular Phylogenetics and Evolution 152: 106938. doi: 10.1016/j.ympev.2020.106938.
https://doi.org/10.1016/j.ympev.2020.106... , bKinosian SP, Pearse WD, Wolf PG. 2020b. There and back again: Reticulate evolution in Ceratopteris. American Fern Journal 110: 193-210. doi: 10.1640/0002-8444-110.4.193.
https://doi.org/10.1640/0002-8444-110.4.... ), particularly among neotropical populations. Therefore, this new record for Peru and for the western Amazon basin opens new opportunities for research in this probably allotetraploid species. Populations of C. thalictroides in Peru were found rooted in inundated soils of irrigation canals of “palmito” fields (Bactris gasipaes Kunth var. gasipaes) together with Limnocharis flava (L.) Buchenau, Heteranthera reniformis Ruiz & Pav. and Sagittaria sp. (Fig. 1 A ) at 180 m elevation, in Caynarachi, 6°11'8.80"S, 76°20'10.64"W, San Martín (F. Peláez 901 HUT, USM). Fronds are mostly erect (Fig. 1 B ), 1-3 pinnate, with 4-6 pairs of pinnae; sterile leaves 31-70 cm long, petiole 12-38 cm long; fertile leaves 33-77 cm long, petiole 21-40 cm (Fig. 1 C , D); abaxial sporangia with inrolled segment margins (Fig. 1 E , F, G) with more than 30 indurated annulus cells (Fig. 1 H ), and trilete spores (Fig. 1 I ).

Figure 1.
Ceratopteris thalictroides. A. Habitat along an irrigation canal, San Martín, Peru. B. Habit showing rooted plants in inundated soils. C. Fertile leaf on the left, sterile leaf on the right. D. Detail of narrow fertile segments. E. Abaxial location of sori. F. Hand-cut transverse section of fertile segment. G- Detail of transverse section showing inrolled segment and a sorus. H. Sporangia. I. Trilete spore. (Photos by F. Pélaez and N. Alarcón).

Key to Ceratopteris in Peru

Plants mostly floating; sterile fronds with inflated petioles; laminae deltoid, pinnatifid with broad segments Ceratopteris pteridoides

Plants rooted aquatics; sterile fronds without inflated petioles; laminae lanceolate, 1-3 pinnate Ceratopteris thalictroides

Acknowledgments

We thank SERFOR for granting collecting permit RDG N^o D000317-2020-MINAGRI-SERFOR-DGGSPFFS. We recognize Kenneth R. Young for comments and reviewing the English prose, and Jorge Torres Delgado (†) for facilitating field work.

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