Phylogeny, systematics, and post‐Eocene radiation in microsoroid ferns (Polypodiaceae)

Microsoroid ferns or Microsoroideae (Polypodiaceae), here estimated to contain ca. 380 species, are endemic to the Old World and Oceania. Previous studies have successfully identified six well‐supported clades and resolved their relationships. However, previous studies were based on relatively small taxon and character samplings, very little has been known about their biogeography, and botanists have not agreed on how many genera in this subfamily should be recognized. Here, we infer their phylogenies based on the largest datasets so far with Sanger‐DNA sequence data of six plastid markers of 830 (160% increase of the latest study) accessions representing ca. 266 (72% increase) species and 117 (303% increase) plastomes representing ca. 90 (221% increase) species of Microsoroideae. Our data resolve microsoroids into five major clades and well resolve the relationships among and within each of these clades. We uncover relationships of a number of species in Microsorum s.l. for the first time. We provide strong evidence that Polypodiastrum is nested within and should be treated as a synonym of Polypodiodes . Our analyses show that Microsoroideae originated ca. 53 Ma in the Paleocene, and the first genus/tribe started to diverge from the rest ca. 48 Ma. Nearly all infra‐tribal diversifications occurred around or right after the Eocene/Oligocene Boundary with major shifts in Earth's climates. Based on morphological and molecular results, we propose to recognize 5 tribes and 22 genera including an existing hybrid genus, a new hybrid genus, and a newly reinstalled genus, Campylogramma . We provide a key to genera and taxonomic synopses of tribes and genera.