Phylogenetic Relationships of Extant Ferns Based on Evidence from Morphology and rbcL Sequences

Abstract

We present the first cladistic analysis of extant ferns based on morphological characters. Our data set consisted of 77 vegetative and reproductive morphological/anatomical characters recorded on a broad sampling of 50 extant pteridophyte taxa, with representatives of all major fern groups, and one seed plant [Cycas). An annotated list of both retained and excluded morphological characters is presented. Results from the morphological analysis are compared with an independent analysis oirbcL data carried out here for the same set of pteridophyte taxa. Finally, we analyze a combined (morphological and molecular) data seL All three data sets were analyzed using maximum parsimony. Two separate sets of analyses using different taxon combinations were conducted on each of the three data sets. Analysis 1 focused on phylogenetic relationships of ferns only (Filicopsida, Botrychium, and Angiopteris], using Cycas as an outgroup representative from the seed plants. Analysis 2 focused on phylogenetic relationships of pteridophytes (Filicopsida, Augiopteris, Botrychium, Equisetum, Psilotum], using Lycopodium as the outgroup. In both sets of analyses, the combined data set provided the most robustly supported hypothesis of relationships. Results from the combined data set in Analysis 1 provided strong bootstrap support for the monophyly of the following clades: leptosporangiate ferns (with Osmunda as the most basal leptosporangiate fern), heterosporous ferns, Cheiropleuria-Dipteris, Diplopterygium-Stromatopteris, tree ferns, schizaeoid ferns, pteridoid ferns, and a large clade consisting of a derived group of leptosporangiate ferns that excludes dennstaedtioids and pteridoids. Various smaller clades within some of these larger clades also have strong support. The dennstaedtioid ferns are paraphyletic. We use the results of the combined data set in Analysis 1 to examine character evolution within the leptosporangiate ferns. Results from the combined data set in Analysis 2 indicated robust support for essentially the same fern clades as the combined data set in Analysis 1. In both Analyses 1 and 2, bootstrap support for the leptosporangiate fern clade is much greater using the combined data set than when either the morphological or, particularly, the molecular data set is analyzed separately. Relationships among major groups of pteridophytes at the base of the tree [Botrychium, Angiopteris, Psilotum, Equisetum, Lycopodium) were poorly supported by the combined data in Analysis 2, except for a weak association between Botrychium and Psilotum. We are convinced from this study of the value of using both molecular and morphological data sets in combination as well as separately. A synthetic approach that integrates paleobotanical and neobotanical data will be of greatest interest in further elucidating the phylogenetic relationships of pteridophytes.Our understanding of the phytogeny of pteridophytes has lagged behind the considerable progress made recently in clarifying the phylogenetic relationships of other green plants, especial...

The Relationship Between Global and Regional Distribution Diminishes Among Phylogenetically Basal Species

“…The underlying phylogeny encompassed the 1514 species of the central European flora and was compiled from 50 sources listed in Prinzing et al (2001). Basically, we took the topological relationships among lower groups of vascular plants from Doyle (1998) and the familial level relationships from Pryer et al (1995) for ferns; Chase et al (1993) for gymnosperms; Graham and Olmstead (2000) for basal angiosperms; Savolainen et al (2000) for dicots; Kubitzki (1998) for monocots excluding Potamogetonales; Haynes et al (1998) for Potamogetonales; and Olmstead and Reeves (1995), Wolfe and dePamphilis (1998), Oxelman et al (1999), and Olmstead et al (2001) for Scrophulariales. The phylogeny did not include microspecies (subspecific segregates without clear taxonomic rank mostly formed by apomicts).…”

Primary cell wall composition of pteridophytes and spermatophytes

“…(2003) show the PCWs of lycopodiophytes (early diverging pteridophytes) to contain xyloglucan endotransglucosylase (XET), an enzyme activity capable of transglycosylating xyloglucan (a cell wall polysaccharide). Additionally, we previously reported (Popper et al ., 2001) that lycopodiophytes, the earliest diverging extant vascular plants (Raubeson & Jansen, 1992;Manhart, 1994Manhart, , 1995Pryer et al ., 1995;Wolf, 1997;Duff & Nickrent, 1999) uniquely contain high concentrations of 3-O -methyl- -galactose (MeGal) in their PCWs. Homosporous lycopodiophytes, bryophytes and charophytes also contain 3-O -methyl-rhamnose (MeRha) in their PCWs (Popper et al ., 2004).…”

Problems in Cladistic Classification: Higher-Level Relationships in Land Plants

“…Mishler and Churchill (l985a,b) Kenrick andCrane (1991, 1997) Kenrick andCrane (1991, 1997) Crane (1990), Kenrick and Crane (1991) Kenrick and Crane (1991 Kenrick and Crane (1991) Pryer et al (1995 Kenrick and Crane (1991) Crane (1985, Doyle and Donoghue (1986), Nixon et al (1994), Rothwell and Serber ( 1994) Chase et al (1993), Doyle et al (1994), Drinnan et al (1994) are the "residue" of green plants after the land plants have been removed. Similarly, "bryophytes" are merely nonvascular land plants, "pteridophytes" are those vascular plants that are not seed plants, and "gymnosperms" are the "residue" of seed plants after angiosperms are excluded.…”

“…Characters supporting a close relationship between the early fossil Jbyka and sphenopsids include i) whorled branching (Stein et al 1984), and ii) protoxylem disintegration to form lacunae (Kenrick andCrane 1997, Skog andBanks 1973). Leptosporangiate ferns (including Osmundaceae) i) distinctive annulate dehiscence of sporangium, ii) superficial antheridia, iii) operculate cell in antheridium, iv) "C" shaped leaf trace (Bierhorst 1971), and v) possibly siphono-dictyostelic anatomy (see also Pryer et al 1995). i) tetrastichous branching, and ii) a distinctive form of protoxylem ontogeny with multiple strands occurring along the mid-planes of the primary xylem ribs , Kenrick and Crane 1997).…”