A Reevaluation of Seed Plant Phylogeny

Abstract

Seed plant phylogeny is evaluated using a data set of 46 terminals (taxa) and 103 morphological and anatomical characters. Cladistic analyses using the criterion of parsimony were performed on the complete data set as well as on subsets of the data, e.g., excluding fossils and/or combining various complex taxa into single terminals. The results support the placement of the cycads as the sister group of a monophyletic group that includes several fossil "seed ferns" as well as extant Ginkgo, conifers, gnetopsids, and angiosperms. When fossils were included, Bennettitales (cycadeoids) were part of an "anthophyte" clade that included gnetopsids and angiosperms. Pentoxylon was a sister taxon to the core anthophyte clade, in some, but not all, of the most parsimonious trees. Caytonia was not found to be closely associated with the anthophyte clade, but instead was often associated as a sister taxon of the glossoptends, and these two taxa were consistently outside of the Gin&go-conifer-anthophyte clade. In all most parsimonious trees for all analyses, Ephedra was to the outside of a clade that included all angiosperm taxa, Gnetum, and Welwitscnia, thus rendering the traditional gnetopsid clade paraphyletic. New information is provided on the morphology of Caytonia and some previous interpretations of homology of the caytonian "cupule" are rejected. The effects of sampling, compartmentalization, and polymorphism are explored in these data, snowing how different results may be obtained when polymorphic or "summary" terminals are used. The need for more work on gnetopsids and fossil taxa is suggested.

Relationships of the Wollemi Pine (Wollemia nobilis) and a molecular phylogeny of the Araucariaceae

“…and Taxaceae. This is in overall agreement with Chaw et al (1995) and Price et al (1993), but differs from Hart (1987), Nixon et al (1994) andMiller (1988). However, the analysis published by Miller was based on a limited number of characters from one organ only (the seed cone) and that of Hart showed a high level of homoplasy.…”

“…Other studies have differed considerably, placing the Araucariaceae as the sister to Pinaceae (Miller 1988;Nixon et al 1994), although differing markedly from each other in the relationships of the other conifer families (Fig. 2).…”

Fossil evidence for a herbaceous diversification of early eudicot angiosperms during the Early Cretaceous

“…Fairlingtonia thyrsopteroides can be confidently assigned to the seed plant clade based on its axillary branching [35,36]. Attached leaves subtend branches (figure 3c) and resting buds occur in the leaf axils ( figure 3a).…”

Recognising angiosperm clades in the Early Cretaceous fossil record

“…Before the advent of molecular systematics, there was speculation that Chloranthaceae might provide an alternative model for the first angiosperms (Burger 1977;Leroy 1983;Endress 1987;Taylor and Hickey 1992;Nixon et al 1994), but this is refuted by molecular data, which uniformly exclude the family from the basal ANITA grade. The combined morphological and molecular analysis of Doyle and Endress (2000), which did not include Ceratophyllum, placed Chloranthaceae at the base of the mesangiosperm clade (Figure 2), in part because they retain the ancestral ascidiate carpel typical of the ANITA lines.…”