Filicopsid

See also: Pteridophyta

The ferns (taxon Filicopsida, Pterophyta, Filicinae or Polypodiophyta) are seedless vascular plants (pteridophytes), whose most outstanding morphological characteristics are their large leaves ("megaphylls" or "fronds"), usually pinnate and with circinate prefoliation. It has traditionally been grouped into 3 groupsː leptosporangiate ferns (Polypodiidae), maratials and ophioglossals, however, modern genetic analyzes found that ophioglossals are related to psilotales, which were historically classified apart as primitive, now being grouped together as one taxon called Ophioglossidae or Psilotopsida. They can present sori for reproduction. The monophyletic nature of ferns has been questioned by several authors due to the results of the first molecular phylogenetic analyses; however, they have been shown to form a sister clade to horsetails based on plastid, nuclear, and mitochondrial genetics. Traditionally they have been grouped into two groups based on the structure and development of the sporangia: maratials and ophioglossals are collectively called "eusporangiate ferns" (but horsetails and psilots are also eusporangiates), and polypods are called "leptosporangiate ferns"; although phylogenetic analyzes determined that the eusporangiates are actually a paraphyletic group relative to the leptosporangiates.

Phylogenetically it can be divided into two groupsː Ophioglossidae (ophioglossales and psilotales) and the group popularly known as "true ferns" (maratials and polypodids) that today, after molecular DNA analysis, have been determined to form a clade (monophyletic group according to the cladist school).

Some species, such as the eagle fern (Pteridium aquilinum) or the azolla (Azolla filiculoides) are extremely common and are found all over the earth's surface.

Etymology

The Spanish word fern, like terms such as Filices or Filicopsida, come from the Latin filix or filicis. A place populated with ferns was called filictum or filectum in Latin.

Phylogeny

Plastid genetic analysis has placed ferns as a sister clade to horsetails, as have nuclear genetic analysis and mitochondrial genetic analysis. The most up-to-date phylogeny (2013–2014) indicates that ferns living creatures form a monophyletic group within the Monilophyta as follows:

It is estimated that the clade of ferns shown here is over 350 million years old, and it can be seen that it has the following two subcladesː

Clade Ophioglossidae

Tmesipteris, a Psilotaceae.

Types of fronds and spores in Ophioglossaceae.

Ophioglossidae or Psilotopsida brings together opioglossales and psilotales. Previously they were not considered one group due to their morphological differences, as Psilotum was thought to be related to primitive leafless pteridophytes such as rhiniophytes. Today it is considered that Psilotum evolutionarily reduced its fronds to scales by having associated with fungi.

This clade is characterized by including small plants, with a reduced root system, the roots do not have root hairs or are absent, and the sporophore is located next to the adaxial face (bundle) of the frond. Exoscopic embryo and gametophyte underground, axial, non-photosynthetic and in mycorrhizal symbiosis (with fungi). The genome is very large, unusual for land plants. The age of the group is estimated at almost 300 million years.

True Ferns

Great deal.

The frond outbreak in the true ferns is shaped like a violin head (circined winter).

Usually, the maratiaceae and leptosporangiate ferns (Polipodiidae) are called true ferns. The characteristics that differentiate them from other ferns are notable, such as the typical compound frond, usually bipinnate, and the circinate vernation (rolled leaf primordium). They present fertile fronds (sporophylls) that contain the sori (sporangia) located below (on the underside) and there are scales. The type of vascular bundle of the leaves is amphicribal or periphloematic, that is, the bundle is concentric and the phloem surrounds the xylem. The gametophyte or prothallus is green (photosynthetic) and is above ground. The age of this clade is estimated to be over 300 million years.

Soros on the abaxial face of a Marattia.

Maratiaceae and leptosporangiate ferns, despite their obvious similarities, have not been considered a formal group and the true ferns thus described have not possessed a scientific name or taxon, except on occasions when they have been called Pteridophyta or Filicophyta (separated from Ophioglossophyta). This is due to two reasonsː First, historical classifications gave taxonomic value to the development of the sporangium (leptosporangium and eusporangium), thus establishing a relationship between maratials and ophioglossals. Secondly, molecular phylogenetic analyzes have been contradictory, obtaining various results, where horsetails sometimes appeared related to Marattiales and/or Polypodiidae or to Ophioglossidae, which caused the Filicopsida taxon to cease to be used in recent taxonomic systems. However, more recent and comprehensive analyzes based on plastid, nuclear, and mitochondrial genetics have supported the unity of ferns, so it is likely that the clade will be assigned a taxon (probably class or subclass) in the future. of the ferns and to the subclade of the true ferns.

Reconstruction of Psaronius, tree of the Marattiales group of Carboniferous.

Extinct groups

Establishing the phylogeny of extinct groups is difficult and speculative. However, some authors have tried to establish these relationships:

Other Considerations

Previous phylogenetic studies considered ferns to be a paraphyletic group, as Monilophyta is presented in the table below:

Figure 5. Philogenetic tree of the different groups of pteridophytes and their relationship with the other groups of terrestrial plants (2002, 2004).

For a discussion of the phylogeny of these groups see the systematics in Pteridophyta. For a basic description of fern morphology see Pteridophyta. The monophyly of this group is disputed: See also Smith's 2006 Monilophyte classification system).

The phylycopsids can be defined as pteridophytes with a sporophyte with: vascular cylinder derived from the siphonostele, megaphylls, sporophyll (sporangia always on the leaves), and sporangia located on the margin or on the abaxial face of the megaphiles. If we are defining the Filicopsida sensu Engler, or the Pterophyta/Pteropsida sensu Bold & al., the sporangia may be eusporangia or leptosporangia. If we are defining the Filicopsida sensu Bold & al., only pterophytes with leptosporangia correspond to this taxon.

Most of them are terrestrial, saxicolous (they live on rocks) or epiphytes, but there are also marshy (continental and coastal) and aquatic ones.

Synonymy

There are several equivalent terms that define ferns, historically they were classified within Pteridophyta. The most widely used term is Filicopsida, which is phylogenetically the most modern group within the pteridophytes. In Engler's classification system, both eusporangiate and leptosporangiate megaphyllous ferns fall within this taxon. In the system accepted by Bold & al. (1989), only the ferns with leptosporangiate megaphylls (Polypodiidae) belong to the taxon Filicopsida, and the ferns with eusporangiate megaphylls together with the leptosporangiates belong to the division Pterophyta (which is therefore synonymous with Filicopsida sensu Engler). Sometimes the pterophytas are not given the division rank but the class rank, when referring to the filicopsids it is essential to clarify according to which classification system they are being defined.

In the 18th century ferns were considered in the family Filices (Linnaeus 1751, Adanson 1763) and were placed inside the "acotyledonous" (Jussieu 1774). In the XIX century the terms Filicoideae (Lindley 1846), Filices (Haeckel 1866), class Filicinae that together with Equisetinae and Lycopodinae formed the division Pteridophyta (Eichler 1883, Engler 1886). In the XX century there are several names: Pteridophyta (Bessey 1907), class Filicopsida (Engler 1924), Filicinae (Wettstein 1924), Pterophyta (Smith 1955, Bold 1957), Polypodiophyta (Cronquist et al 1966), Filicatae (Kubitzki et al. 1990-), Filicinophyta (Margulis et al 1998) and less commonly used names such as Filicophyta, Filicinlophyta, Filicophytina, and the classes Polypodiopsida and Pteropsida.

In this century, in light of conflicting molecular phylogenetic analyses, it has been preferred not to assign any taxa to ferns, nor to true ferns. However, APWeb (2015) refers to the clade ((Psilotales + Ophioglossales) (Marattiopsida + Polypodiopsida)).

Classification

Historically they have been classified into different groups:

Sensu Engler

Older traditional classifications such as Engler's had lumped together all "ferns" in the same clade, Filicopsida being the class in which the "ferns with megaphylls" were grouped, today known as the Polypodiopsida, Marattiopsida and Ophioglossaceae clades. Within "Filicopsida" (sensu Engler), Engler had realized that the eusporangiate ferns were more primitive, and probably not related to each other, so the Ophioglossaceae and Marattiaceae were placed in his own subclass. With regard to the leptosporangia, he did not conceive of them as a clade, leaving the more modified leptosporangia in their own subclass: thus the Osmundaceae (with their primitive leptosporangium with a lateral ring), the Marsileaceae and the Salviniaceae had their own subclasses. He also did not relate the heterosporate ferns Marsileaceae and Salviniaceae as siblings, since their sporocarps seemed to have different origins, and he assumed that their resemblances were a convergence due to the transition to aquatic habit, rather than the result of descent from a common ancestor (for one interesting discussion about the homologies in the sporocarp of the Marsileaceae and Salviniaceae (see Salviniales, clade where the two families are grouped today).

In summary, the sensu Engler classification is as follows:

Taxonomic classification

. TAXONOMY AND MORPHOLOGY

Ferns are plants without flowers or seeds, belonging to the group of Pteridophytes. They reproduce by means of spores, which need the presence of water to complete their biological cycle. Ferns are notable for:

• Its leaves (fronds).

•Its underground stem (rhizomatous).

•Your particular reproduction.

•Its numerous genera and species.

• Kingdom Plantae
  • Embryophyta asphonogama (paraphylaxis)
    • Pteridophyta (paraphytic) Branch
      • Class "Filicopsy"sensu Engler) (equivalent to Polypodiopsyda sensu Smith et al. + Ophioglossaceae + Marattiopsida), divided into subclasses:
        • Marattidae (monophylical, equivalent to Marattiopsida sensu Smith et al.)
        • Ophioglossidae (monophyletic, equivalent to Ophioglossaceae sensu Smith et al.)
        • Osmundidae (monophyletic, equivalent to Osmundales sensu Smith et al.)
        • Filicidae (paraphylically with respect to heterosporates, equivalent to clado inside Polypodiopsyda sensu Smith et al. which remains if the osmundaceae are left out, which is paralysed when the heterosporates are also removed)
        • Marsileidae (monophylaxis, equivalent to Marsileaceae sensu Smith et al.)
        • Salviniidae (monophylical, equivalent to Salviniaceae sensu Smith et al.)

Pterophyta (Pteropsy if class)

• division Pterophytadivided into classes:
  • Ophioglossopsida
  • Marattiopsida
  • Filicopsida (as equivalent to Polipodiidae)

The filicopsid sporophyte

It is a corm without secondary growth, with adventitious roots, siphonostela, megaphylls, sporangia on the margin or abaxial face of megaphylls. The prefoliation is circinate, characteristic of ferns (if in Engler's classification system, with the exception of the subclass Ophioglossidae, where the prefoliation is folded with stipules forming sheaths).

Leptosporangia may have opening by apical stomium (Osmundaceae), by functional ring (Filicidae), or they may not have specialized parts of the wall opening (Marsileaceae, Salviniales).

Reproduction in filicopsids

Cycle of life of true ferns, graphing the alternation of generations between the sporophyte and the gametophyte.

Normally ferns have megaphylls that can be:

• Temporary Trophosporophiles (Leaves that at one time of the year are throphophiles—daughters that take photosynthesis—and in another are sporophiles—sheets that carry spanges). Examples we find in Marattidae, some orders from Filicidae.
• Sectoral metaphors (Leaves that in one sector are photosynthetic and in another sector are carriers of sporangios). Examples in Ophioglossidae, Osmundidae, some orders from Filicidae, the aquatic ferns Marsileidae and Salviniidae.
• Swords (sheeps that fully fulfill the function of being sporang carriers). Examples: some Osmundidae.

The spores can give male and female gametes (isosporous sporophytes), or there can be 2 morphs of spores that will give different sexes of the gametophyte (heterosporated sporophytes), in this case they are called megaspores (those that will give female gametophyte with female gametes) and microspores (those that will give a male gametophyte with male gametes). All Filicopsida subtaxa are isosporous, except for the Marsileaceae and Salviniales, both taxa adapted for aquatic or marsh life, which are heterosporous.

Under the microscope, two spore morphs can be observed, which can be trilete or monolete, a character used to determine families.

Filicopsid Systematics

Engler Classification System

Unlike the other classification system, Engler groups both eusporangiate and leptosporangiate ferns into the Filicopsids. Thus, the Marattiaceae and Ophioglossidae fall within this taxon.

The Engler classification system divides the Filicopsids into 7 subclasses, one of extinct representatives:

1. Primophilia. Subclass of extinct representatives, with two orders: Cladoxylales and Coenopteridales.
2. Ophioglossidae. Isopular sporaphites, eusporangized. Sectoral trophosporophiles (in this subclass the fertile pines are called spikes). Eusporangios in synangios or parrots in the last pins of trophosporofyl. Trilet spores. Folded prefoliation with stipules forming vain. They need a lot of water to live. Mycorrhizal roots (which are associated with fungi). Gametófito also micorrícico and tuberoso. An order: Ophioglossales, only family: Ophioglossaceae.
3. Marattidae. Isopular sporaphites, eusporangized. Temporary troops. Sporangios in synangios or parrots. Trilet spores. Put it on. Surcined prefoliation. Allied stypules. An order: Marattiales, only family: Marattiaceae.
4. Osmundidae. Isopian sporaphites. Leptosporangios with apical ape and shield (according to some authors, their morphology is intermediate between eusporangiados and leptosporangiados). Swords or sectoral trophosporophiles. Surcined prefoliation. Trilet spores. Osmundales, the only family: Osmundaceae.
5. Filicidae. Isopian sporaphites. Leptosporangios with functional ring. Surcined prefoliation. Many orders and families. The commonly called "facts."
6. Marsileidae. Heterospore sporophites. Leptosporangios without a ring or with a weakly marked non-functional ring on the apical part. Leptosporangiums locked in spores. Surcined prefoliation. They only live on permanent water grounds. An order: Marsileales, the only family: Marsileaceae.
7. Salviniidae. Heterospore sporophites. Leptosporangios without a ring, in parrots locked in spores. Surcined prefoliation. Floating plants. Order Salviniales, two families (sometimes seen as two genera of the same family): Salviniaceae, Azollaceae.

Gallery

• 

  Psilotum

• 

  Ophioglossum

• 

  Marattia

• 

  Polypodium

• 

  Salvinia

• 

  Osmunda

• 

  Hymenophyllum

• 

  Schizaea

• 

  Giant oil in New Caledonia (Cyatheaceae)

• 

  Brochure Cyathea

• 

  Adiantum pedatum

• 

  Wild Facts in the Sierra de Zacatecas (Mexico)

• 

  Pteris