Polyphlebium borbonicum (Bosch) Ebihara & Dubuisson, Blumea

Kessler, Michael & Smith, Alan R., 2017, Prodromus of a fern flora for Bolivia. X. Hymenophyllaceae, Phytotaxa 328 (3), pp. 201-226 : 218

Polyphlebium borbonicum (Bosch) Ebihara & Dubuisson, Blumea 51: 240. 2006.

= Trichomanes borbonicum Bosch, Ned. Kruidk. Arch. 5(2): 158. 1861.

= Trichomanes debile Bosch, Ned. Kruidk. Arch. 5(2): 154. 1861.

Range: —Northern Venezuela to Bolivia (CO, LP); Madagascar, Mascarenes, Comores, continental Africa, and Polynesia.

Ecology: —Uncommon; epiphytic in humid forests; 550–2750 m.

Notes: —Generally differs from Polyphlebium diaphanum by fewer, more strongly ascending pinnae with longer (to 15 mm vs. <5 mm long) unbranched segments. The pinnae of P. diaphanum are juxtaposed or approximate, while those of P. borbonicum are well-separated. Petioles of P. borbonicum are unwinged, or distally with narrow wings; blades are 1- to 2-pinnate, to 25 mm wide, with pinnules strongly ascending, set 40–60° to rachises. Molecular data also support separation from congeners, as well as its amphioceanic, essentially austral distribution ( Nitta 2008; Ebihara et al. 2009). However, distinctions between the two species have been questioned by Ponce et al. (2017). In their analysis, P. borbonicum is perhaps monophyletic only if most specimens identified as P. hymenophylloides and Trichomanes debile are included.

Specimens from Bolivia identified as Polyphlebium hymenophylloides (Bosch) Ebihara & Dubuisson [syn. = Trichomanes hymenophylloides Bosch ], from the Antilles, Mexico to Ecuador and Venezuela, and southern Brazil, seem to be referable to P. borbonicum . Limited sampling by Ponce et al. (2017) supports this conclusion. In P. borbonicum , the petioles are unwinged or distally with short wings; blades 2- or 3-pinnate, to 15–40 mm wide; pinnules moderately ascending, set 55–70° to rachises. Polyphlebium hymenophylloides supposedly differs in having large, more dissected blades with the pinnae not as ascending, but these characters may not hold. Less dissected, juvenile, or perhaps precociously fertile specimens, sometimes called Trichomanes debile , also appear to be Polyphlebium borbonicum ( Ponce et al. 2017) .