SMITH, ALAN R.* and RAYMOND B. CRANFILL. University Herbarium, University of California, Berkeley, CA 94720. - Intrafamilial relationships of the thelypteroid ferns (Thelypteridaceae).
Since its separation from the dryopteroid ferns as a distinct group,
about 60 years ago, Thelypteridaceae has been treated as a natural
group comprising nearly 1000, mostly tropical species. Although
generally recognized as a natural monophyletic group, there is a wide
divergence of views about generic circumscription. Morton placed all
species in a single genus Thelypteris; Holttum characterized
25 genera in the Old World alone; Pichi Sermolli, largely following
Holttum, accepted 32 genera; while Smith adopted an intermediate
view, recognizing 5 genera. Most of the paleotropical segregates, and
several of the neotropical ones, have been recently revised or
monographed, making this one of the best known fern families
morphologically, cytologically, and distributionally. Little,
however, is known about relationships between these segregates. Data
from four chloroplast genes (rps4 + rbcL + trnS
spacer, + trnL spacer; 2600 base pairs) for 23 of the
recognized segregates show the family to be monophyletic and sister
to an unresolved alliance of blechnoid, athyrioid, onocleoid, and
woodsioid ferns. The family itself comprises two primary lineages,
one phegopterid, the other thelypterid. The phegopterid lineage
includes those elements within Thelypteridaceae that are the most
dissected and morphologically distinct: Macrothelypteris,
Pseudophegopteris, and Phegopteris. Within the thelypterid
lineage, three predominantly north-temperate subgroups, including
Thelypteris s.s., form a free-veined clade that is in turn
sister to the rest of the family. All segregates possessing x
=36 (Cyclosorus sensu Smith, with predominantly anastomosing
veins) form a strongly supported clade. Those groups with dysploid
base chromosome numbers (x=27, 29, 30, 31, 33, 34, 35) form a series
of smaller clades basal to Cyclosorus s.l. Although our
sampling is as yet insufficient to favor one classification over
another, the present analysis suggests that recognition of an
intermediate number of genera may be the most reasonable taxonomic
course.
Key words: and trnS spacer, phylogeny, rbcL, rps4, Thelypteridaceae, trnL spacer