As described in Nitta et al. 2020, this is likely an apogamous hybrid with Polyphlebium capillaceum (L.) Ebihara & Dubuisson as the mother, with which it shares nearly identical rbcL sequences. The other parent of the hybrid is unknown. Polyphlebium capillaceum has laminae reduced to just one or a few cells on either side of the veins, but Polyphlebium sp1 has more expanded laminae. Furthermore, Polyphlebium sp1 has 32 spores per sporangium, a condition that often indicates asexual reproduction via apogamy.

References

Nitta, Joel H., Atsushi Ebihara, and Alan R. Smith. “A taxonomic and molecular survey of the pteridophytes of the Nectandra Cloud Forest Reserve, Costa Rica.” PLOS ONE 15.11 (2020): e0241231. https://doi.org/10.1371/journal.pone.0241231