|Order:|| Pinales |
| Pinus |
(approximate number of species in parentheses)
The order Pinales in the division Pinophyta, class Pinopsida, comprises all the extant conifers. The distinguishing characteristic is the reproductive structure known as a cone produced by all Pinales. All of the extant conifers, such as cedar, celery-pine, cypress, fir, juniper, larch, pine, redwood, spruce, yew and Araucaria araucana ("Monkey tail tree" or "Monkey puzzle tree") are included here. Some fossil conifers, however, belong to other distinct orders within the division Pinophyta.
Multiple molecular studies indicate this order being paraphyletic with respect to Gnetales, with studies recovering Gnetales as either a sister group to Pinaceae or being more derived than Pinaceae but sister to the rest of the group.
Brown (1825)first discerned that there were two groups of seed plants, distinguished by the form of seed development, based on whether the ovules were exposed, receiving pollen directly, or enclosed, which do not. Shortly afterwards, Brongniart (1828) coined the term Phanérogames gymnosperms to describe the former group. The distinction was then formalized by Lindley (1830), dividing what he referred to as the subclass Dicotyledons into two tribes, Gymnosperms and Angiosperms. In the gymnosperms (or Gymnospermae) Lindley included two orders, the Cycadeae and the Coniferae. In his final work (1853) he described Gymnogens as a class with four orders;
In contrast, Bentham and Hooker (1880) included only three orders in the class Gymnospermeae, by including taxads within Coniferae;
In the Engler system (1903) Gymnospermae is listed as a subdivision (Unterabteilung) and adopted more of a splitter approach, including extinct taxa, with the following six classes;
During this period, Gorozhankin published his treatise on Gymnosperms (1895), for which he bears the botanical authority for Pinales, Gorozh.. In his classification, Gymnospermae (alternatively named Archespermae) was a class of the division Archegoniatae, divided into subclasses;
A system of two groups was maintained by the most commonly used classification in the twentieth century,the revision of the Engler system by Pilger (1926), who grouped 12 families of the Gymnospermae subdivision into 2 classes;
The treatment of Gymnosperms as two groups, though with varying composition and names, was followed for most of the twentieth century, including the systems of Chamberlain (1935),Benson (1957) and Cronquist (1960).
In the latter, Cronquist divided Gymnospermae into two divisions;
Benson,(1957)who introduced the term Pinales, divided gymnosperms into four classes;
In a later revision, in collaboration with two other taxonomists (1966), Cronquist merged all the gymnosperms into a single division, Pinophyta, with three subdivisions reflecting the main lineages;
In the era of molecular phylogenetics, De-Zhi and colleagues (2004) once again proposed a division of 12 gymnosperm families into two classes;
With the development of the Angiosperm Phylogeny Group came a major realignment of the linear classification of the land plants, by Chase and Reveal (2009). In this system, the land plants form a class, Equisetopsida s.l. (sensu lato) or sensu Chase & Reveal,also known as embryophytes or Embryophyceae nom. illeg. . Class Equisetopsida s.l. is divided into 14 subclades as subclasses, including Magnoliidae (angiosperms). The gymnosperms are represented by four of these subclasses, placing them in a sister group relationship to angiosperms. Subclasses (number of orders);
Gymnosperm (Acrogymnospermae) taxonomy has been considered controversial, and lacks consensus.As taxonomic classification transformed from being based solely on plant morphology to molecular phylogenetics, the number of taxonomic publications increased considerably after 2008, however, these approaches have not been uniform. A taxonomic classification has been complicated by the relationship of extant to extinct taxa, and within extinct taxa, and particularly the placement of Gnetophyta. The latter have been variously classified as basal to all gymnosperms, sister group to conifers (‘gnetifer’ hypothesis) or sister to Pinaceae (‘gnepine’ hypothesis) in which they are classified within the conifers. While the extant gymnosperms form a monophyletic group, a formal name has not been assigned to this clade. In 2018, the Gymnosperm Phylogeny Group was established, analogous to the Angiosperm Phylogeny Group and Pteridophyte Phylogeny Group, with the intention of reaching a consensus.
Gymnosperms form a group of four subclasses among the spermatophytes (seed bearing plants). In turn, the seed plants together with the monilophyte fern subclasses make up the tracheophytes (vascular plants), part of the class Equisetopsida (embryophytes or land plants), as opposed to the green algae. Among the seed plants, the gymnosperms are a sister group to the subclass Magnoliidae (angiosperms or flowering plants).
There are about 1000 extant gymnosperm species, distributed over about 12 families and 83 genera. Many of these genera are monotypic (41%), and another 27% are oligotypic (2–5 species).The four subclasses have also been treated as divisions of the Spermatophytes. Alternative names and the approximate number of genera and species in each are;
The term Pinophyta has also been used to include all conifers, extinct and extant, with Pinales representing all the extant conifers.
Christenhusz and colleagues extended the system of Chase and Revealto provide a revised classification of gymnosperms in 2011, based on the above four subclades. In this scheme, the Pinidae comprise three orders, including Pinales, and 6 families;
However, the exact phylogeny remained a topic that was 'hotly debated", in particular whether the main lineages were best represented by the four subclasses of Christenhusz and colleagues or the more traditional five clades (cycads, ginkgos, cupressophytes, Pinaceae and gnetophytes).In 2014 the first complete molecular phylogeny was published, based on 90 species representing all extant genera. This established cycads as the basal group, followed by Ginkgoaceae, as sister to the remaining gymnosperms, and supporting the ‘gnepine’ hypothesis. This analysis favours the five clade hypothesis, the remaining clade following divergence of the Pinidae, are referred to as the conifer II clade, or cupressophytes, in distinction from the conifer I clade (Gnetidae, Pinidae). This clade, in turn, has two lineages. The first consisting of Sciadopityaceae and the Araucariales, the second being the Cupressales. In the Christenhusz scheme, the Sciadopityaceae were considered to be within Cupressales. The term Cupressaceae s.l. refers to the inclusion of Taxodiaceae. These relationships are shown in this cladogram, although no formal taxonomic revision was undertaken.
|Phylogeny of Gymnosperms, subclasses, orders, families|
A more comprehensive analysis was undertaken by Ran and colleagues in 2018, as part of a detailed phylogeny of all seed plants.This forms the basis of the Tracheophyte Phylogeny Poster and the Angiosperm Phylogeny Website.
Historically conifers, in the order Pinales have been considered to consist of six to seven extant families, based on the classification of class Coniferae by Pilger (1926), considered the standard through most of the twentieth century.These families were treated as a single order, in distinction to some earlier systems. His families were;
Subsequent revisions merged the Taxodiaceae and Cupressaceae, and placed Sciadopitys , formerly in Cupressaceae, into a separate family (Sciadopityaceae).Cephalotaxaceae had previously been recognized as a separate family, but was subsequently included in Taxaceae. Similarly Phyllocladaceae were included in Podocarpaceae. Yews (Taxaceae) have sometimes been treated as a separate order (Taxales).
Christenhusz and colleagues (2011) included only one family in Pinales, Pinaceae,a practice subsequently followed by the Angiosperm Phylogeny Website and the Gymnosperm Database. In this restricted model Pinales (Pinaceae) comprisea 11 genera and about 225 species, all of the other conifers originally included in this order, being included in other orders such as Cupressales.
Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta, also known as Coniferophyta or Coniferae. The division contains a single extant class, Pinopsida. All extant conifers are perennial woody plants with secondary growth. The great majority are trees, though a few are shrubs. Examples include cedars, Douglas-firs, cypresses, firs, junipers, kauri, larches, pines, hemlocks, redwoods, spruces, and yews. As of 1998, the division Pinophyta was estimated to contain eight families, 68 genera, and 629 living species.
Araucariaceae – also known as araucarians – is an extremely ancient family of coniferous trees. The family achieved its maximum diversity during the Jurassic and Cretaceous periods, when it was distributed almost worldwide. Most of the Araucariaceae in the Northern Hemisphere vanished in the Cretaceous–Paleogene extinction event, and they are now largely confined to the Southern Hemisphere, except for a few species of Agathis in Southeast Asia.
Gnetophyta is a division of plants, grouped within the gymnosperms, that consists of some 70 species across the three relict genera: Gnetum, Welwitschia, and Ephedra. Fossilized pollen attributed to a close relative of Ephedra has been dated as far back as the Early Cretaceous. Though diverse in the Early Cretaceous, only three families, each containing a single genus, are still alive today. The primary difference between gnetophytes and other gymnosperms is the presence of vessel elements, a system of conduits that transport water within the plant, similar to those found in flowering plants. Because of this, gnetophytes were once thought to be the closest gymnosperm relatives to flowering plants, but more recent molecular studies have brought this hypothesis into question.
Taxaceae, commonly called the yew family, is a coniferous family which includes six extant and two extinct genera, and about 30 species of plants, or in older interpretations three genera and 7 to 12 species.
Proteales is an order of flowering plants consisting of three families. The Proteales have been recognized by almost all taxonomists.
The gymnosperms are a group of seed-producing plants that includes conifers, cycads, Ginkgo, and gnetophytes, forming the clade Gymnospermae, the living members of which are also known as Acrogymnospermae. The term gymnosperm comes from the composite word in Greek: γυμνόσπερμος, literally meaning 'naked seeds'. The name is based on the unenclosed condition of their seeds. The non-encased condition of their seeds contrasts with the seeds and ovules of flowering plants (angiosperms), which are enclosed within an ovary. Gymnosperm seeds develop either on the surface of scales or leaves, which are often modified to form cones, or solitary as in yew, Torreya, Ginkgo. Gymnosperms show alternation of generations; and have a dominant diploid sporophytic phase, a reduced haploid gametophytic phase which is dependent on the sporophytic phase.
The Pinaceae, pine family, are conifer trees or shrubs, including many of the well-known conifers of commercial importance such as cedars, firs, hemlocks, larches, pines and spruces. The family is included in the order Pinales, formerly known as Coniferales. Pinaceae are supported as monophyletic by their protein-type sieve cell plastids, pattern of proembryogeny, and lack of bioflavonoids. They are the largest extant conifer family in species diversity, with between 220 and 250 species in 11 genera, and the second-largest in geographical range, found in most of the Northern Hemisphere, with the majority of the species in temperate climates, but ranging from subarctic to tropical. The family often forms the dominant component of boreal, coastal, and montane forests. One species, Pinus merkusii, grows just south of the equator in Southeast Asia. Major centres of diversity are found in the mountains of southwest China, Mexico, central Japan, and California.
Cupressaceae is a conifer family, the cypress family, with worldwide distribution. The family includes 27–30 genera, which include the junipers and redwoods, with about 130–140 species in total. They are monoecious, subdioecious or (rarely) dioecious trees and shrubs up to 116 m (381 ft) tall. The bark of mature trees is commonly orange- to red- brown and of stringy texture, often flaking or peeling in vertical strips, but smooth, scaly or hard and square-cracked in some species.
Cephalotaxaceae is a small grouping of conifers, that included one to three genera closely allied to Taxaceae. However, members of Cephalotaxaceae are now included in Taxaceae by botanists, instead of as a distinct family, based on phylogenetic evidence and close morphological similarities between them. Included species were restricted to east Asia, except for two species of Torreya found in the southwest and southeast of the United States; fossil evidence shows a much wider prehistorical Northern Hemisphere distribution. The most notable differences between Taxaceae and Cephalotaxaceae concerned the cone aril, which fully encloses the seeds of Cephalotaxaceae, the longer maturation of Cephalotaxaceae seeds and the larger size of the mature seeds.
A pteridophyte is a vascular plant that disperses spores. Because pteridophytes produce neither flowers nor seeds, they are sometimes referred to as "cryptogams", meaning that their means of reproduction is hidden. Ferns, horsetails, and lycophytes are all pteridophytes. However, they do not form a monophyletic group because ferns are more closely related to seed plants than to lycophytes. "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. Ferns 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.
Torreya is a genus of conifers comprising six or seven species placed in the family Taxaceae, though sometimes formerly placed in Cephalotaxaceae. Four species are native to eastern Asia; the other two are native to North America. They are small to medium-sized evergreen trees reaching 5–20 m, rarely 25 m, tall. Common names include nutmeg yew.
Welwitschiaceae is a family of plants of the order Gnetales with one living species, Welwitschia mirabilis, found in southwestern Africa. Three fossil genera have been recovered from the Crato Formation – late Aptian strata located in the Araripe Basin in northeastern Brazil, with one of these also being known from the early Late Cretaceous (Cenomanian-Turonian) Akrabou Formation of Morocco.
The Kubitzki system is a system of plant taxonomy devised by Klaus Kubitzki, and is the product of an ongoing survey of vascular plants, entitled The Families and Genera of Vascular Plants, and extending to 15 volumes in 2018. The survey, in the form of an encyclopedia, is important as a comprehensive, multivolume treatment of the vascular plants, with keys to and descriptions of all families and genera, mostly by specialists in those groups. The Kubitzki system served as the basis for classification in Mabberley's Plant-Book, a dictionary of the vascular plants. Mabberley states, in his Introduction on page xi of the 2008 edition, that the Kubitzki system "has remained the standard to which other literature is compared".
The Polypodiidae, commonly called leptosporangiate ferns, formerly Leptosporangiatae, are one of four subclasses of ferns, and the largest of these, being the largest group of living ferns, including some 11,000 species worldwide. The group has also been treated as the class Pteridopsida or Polypodiopsida, although other classifications assign them a different rank. Older names for the group include Filicidae and Filicales, although at least the "water ferns" were then treated separately.
The spermatophytes, also known as phanerogams or phaenogams, comprise those plants that produce seeds, hence the alternative name seed plants. They are a subset of the embryophytes or land plants.
Ginkgoidae is a subclass of Equisetopsida in the sense used by Mark W. Chase and James L. Reveal in their 2009 article "A phylogenetic classification of the land plants to accompany APG III." This subclass contains the single extant genus Ginkgo under order Ginkgoales, family Ginkgoaceae. Its only extant species is Ginkgo biloba, the Maidenhair Tree.
Gnetidae is a subclass of Equisetopsida in the sense used by Mark W. Chase and James L. Reveal in their 2009 article "A phylogenetic classification of the land plants to accompany APG III." This subclass comprises the gnetophytes. The Gnetidae subclass is equivalent to the division Gnetophyta and class Gnetopsida of previous treatments.
Pinidae is a subclass of Equisetopsida in the sense used by Mark W. Chase and James L. Reveal in their 2009 article "A phylogenetic classification of the land plants to accompany APG III." This subclass comprises the conifers. The Pinidae subclass is equivalent to the division Pinophyta and class Pinopsida of previous treatments. There are over 600 species of Pinidae all over the world.