Online

Fawcett, Susan E

Plant Biology

2020

Ph. D.

The Thelypteridaceae is among the largest fern families, with over 1000 species, and comprises about 10% of all fern diversity. The family is cosmopolitan and most diverse near the equator, although species range as far north as Greenland and Alaska, and as far south as southern New Zealand. The generic classification of the Thelypteridaceae has been the subject of much controversy among authors. Proposed taxonomic systems have varied from recognizing more than 1000 species in the family within a single genus, Thelypteris, to systems favoring upwards of 30 genera. Insights on intrafamilial relationships have been gained from recent phylogenetic studies, especially for the Neotropics, however, in the most recent classification, 10 of 30 recognized genera are either non-monophyletic or untested. In the present study, we sequenced nDNA across 400 loci for 621 accessions, representing all recognized genera. Our phylogenetic results, coupled with morphological study, provide a foundation for our new generic classification system. Major taxonomic changes include the recircumscription of 14 genera, descriptions of four new genera and three subgenera, the elevation of three sections to generic status, the resurrection of one genus, the inclusion of two genera in synonymy, and 181 new combinations. Our newly recognized monophyletic genera demonstrate greater geographic coherence than previous taxonomic concepts suggested. Additionally, our results demonstrate that certain morphological characters, such as frond division, are evolutionarily labile, and are the result of repeated instances of convergent evolution, and are thus inadequate for defining genera.