– lycophytes: clubmosses, quillworts and spikemosses 3 extant orders The system put forward by the Pteridophyte Phylogeny Group in 2016, PPG I, is: Pteridophytes consist of two separate but related classes, whose nomenclature has varied. The two major groups previously included in Pteridophyta are phylogenetically related as follows: Tracheophyta – vascular plants These subclasses correspond to Smith's four classes, with Ophioglossidae corresponding to Psilotopsida. Subclass Polypodiidae Cronquist, Takht. Polypodiophyta (ferns) 4 subclasses, 11 orders, 21 families, approx.Lycopodiophyta (lycopods) 1 subclass, 3 orders, each with one family, 5 genera, approx.In 2014 Christenhusz and Chase, summarising the known knowledge at that time, treated this group as two separate unrelated taxa in a consensus classification įurthermore, within the Polypodiopsida, the largest grouping, a number of informal clades were recognised, including leptosporangiates, core leptosporangiates, polypods (Polypodiales), and eupolypods (including Eupolypods I and Eupolypods II). Ferns, despite forming a monophyletic clade, are formally only considered as four classes ( Psilotopsida Equisetopsida Marattiopsida Polypodiopsida), 11 orders and 37 families, without assigning a higher taxonomic rank. However both Infradivision and Moniliformopses are also invalid names under the International Code of Botanical Nomenclature. This is not a natural grouping but rather a convenient term for non-fern, and is also discouraged, as is eusporangiate for non-leptosporangiate ferns. The term " fern ally" included under Pteridophyta generally refers to vascular spore-bearing plants that are not ferns, including lycopods, horsetails, whisk ferns and water ferns ( Marsileaceae, Salviniaceae and Ceratopteris), and even a much wider range of taxa. By comparison "lycopod" or lycophyte (club moss) means wolf-plant. In fact the alternative name Filicopsida was already in use. Christenhusz and Chase (2014) in their review of classification schemes provide a critique of this usage, which they discouraged as irrational. The term "moniliform" as in Moniliformopses and monilophytes means "bead-shaped" and was introduced by Kenrick and Crane (1997) as a scientific replacement for "fern" (including Equisetaceae) and became established by Pryer et al. In Smith's molecular phylogenetic study the ferns are characterised by lateral root origin in the endodermis, usually mesarch protoxylem in shoots, a pseudoendospore, plasmodial tapetum, and sperm cells with 30-1000 flagella. Historically both lycophytes and monilophytes were grouped together as pteridophytes (ferns and fern allies) on the basis of being spore-bearing ("seed-free"). Where the monilophytes comprise about 9,000 species, including horsetails ( Equisetaceae), whisk ferns (Psilotaceae), and all eusporangiate and all leptosporangiate ferns. Infradivision Spermatophyta - seed plants, ~260,000 species.Infradivision Moniliformopses ( monilophytes).Sub division Euphyllophytina (euphyllophytes).Subdivision Lycopodiophyta (lycophytes) - less than 1% of extant vascular plants.Division Tracheophyta (tracheophytes) - vascular plants.(2006), the first higher-level pteridophyte classification published in the molecular phylogenetic era, considered the ferns as monilophytes, as follows: Of the pteridophytes, ferns account for nearly 90% of the extant diversity. Their other common characteristics include vascular plant apomorphies (e.g., vascular tissue) and land plant plesiomorphies (e.g., spore dispersal and the absence of seeds). The leaves may be microphylls or megaphylls. The stem is either underground or aerial. The body of the sporophyte is well differentiated into roots, stem and leaves. Pteridophytes (ferns and lycophytes) are free-sporing vascular plants that have a life cycle with alternating, free-living gametophyte and sporophyte phases that are independent at maturity. "Pteridophyta" is thus no longer a widely accepted taxon, but the term pteridophyte remains in common parlance, as do pteridology and pteridologist as a science and its practitioner, respectively.įerns and lycophytes share a life cycle and are often collectively treated or studied, for example by the International Association of Pteridologists and the Pteridophyte Phylogeny Group. However, they do not form a monophyletic group because ferns (and horsetails) are more closely related to seed plants than to lycophytes. Because pteridophytes produce neither flowers nor seeds, they are sometimes referred to as " cryptogams", meaning that their means of reproduction is hidden.įerns, horsetails (often treated as ferns), and lycophytes ( clubmosses, spikemosses, and quillworts) are all pteridophytes. Informal paraphyletic group of vascular plants that reproduce by sporesĪ pteridophyte is a vascular plant (with xylem and phloem) that disperses spores.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |