Mesangiospermae (core angiosperms) is a clade of

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants t ...

s (angiosperms), informally called "mesangiosperms". They are one of two main groups of angiosperms. It is a name created under the rules of the '' PhyloCode'' system of phylogenetic nomenclature. There are about 350,000

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriat ...

of mesangiosperms.Alan J. Paton, Neil Brummitt,

Rafaël Govaerts Rafaël Herman Anna Govaerts (born 1968) is a Belgian botanist. He is particularly noted for his work on plant taxonomy. He has worked at the Royal Botanic Gardens, Kew since the 1990s, and is the principal contributor to the World Checklist ...

, Kehan Harman, Sally Hinchcliffe, Bob Allkin, & Eimear Nic Lughadha (2008). "Towards Target 1 of the Global Strategy for Plant Conservation: a working list of all known plant species - progress and prospects". ''Taxon'' 57(2):602-611. The mesangiosperms contain about 99.95% of the flowering plants, assuming that there are about 175 species not in this group Peter F. Stevens (2001 onwards). Angiosperm Phylogeny Website In: Missouri Botanical Garden Website. (see ''External links'' below). and about 350,000 that are. While such a clade with a similar circumscription exists in the APG III system, it was not given a name.

Phylogeny

Besides the mesangiosperms, the other groups of flowering plants are Amborellales, Nymphaeales, and Austrobaileyales. These constitute a paraphyletic grade called basal angiosperms. The

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of ...

names, ending in -ales are used here without reference to taxonomic rank because these groups contain only one order. Mesangiospermae includes the following clades: * Ceratophyllales *

Chloranthales Chloranthaceae is a family of flowering plants (angiosperms), the only family in the order Chloranthales. It is not closely related to any other family of flowering plants, and is among the early-diverging lineages in the angiosperms. They ar ...

eudicots The eudicots, Eudicotidae, or eudicotyledons are a clade of flowering plants mainly characterized by having two seed leaves upon germination. The term derives from Dicotyledons. Traditionally they were called tricolpates or non-magnoliid dicot ...

* magnoliidae * monocots

Name

The mesangiosperms are usually recognized in classification

systems A system is a group of interacting or interrelated elements that act according to a set of rules to form a unified whole. A system, surrounded and influenced by its environment, is described by its boundaries, structure and purpose and expresse ...

that do not assign groups to

taxonomic rank In biological classification, taxonomic rank is the relative level of a group of organisms (a taxon) in an ancestral or hereditary hierarchy. A common system consists of species, genus, family, order, class, phylum, kingdom, domain. While ...

. The name Mesangiospermae is a branch-modified node-based name in phylogenetic nomenclature. It is defined as the most inclusive crown clade containing '' Platanus occidentalis'', but not ''

Amborella trichopoda ''Amborella'' is a monotypic genus of understory shrubs or small trees endemic to the main island, Grande Terre, of New Caledonia in the southwest Pacific Ocean. The genus is the only member of the family Amborellaceae and the order Ambor ...

'', ''

Nymphaea odorata ''Nymphaea odorata'', also known as the American white waterlily, fragrant water-lily, beaver root, fragrant white water lily, white water lily, sweet-scented white water lily, and sweet-scented water lily, is an aquatic plant belonging to the ge ...

'', or '' Austrobaileya scandens''.Philip D. Cantino, James A. Doyle, Sean W. Graham, Walter S. Judd, Richard G. Olmstead,

Douglas E. Soltis Douglas Soltis is a Distinguished Professor in the Laboratory of Molecular Systematics & Evolutionary Genetics, (Soltis lab.) Florida Museum of Natural History and Department of Biology at the University of Florida. His research interests are in ...

, Pamela S. Soltis, and Michael J. Donoghue. 2007. Electronic Supplement: pages E1-E44. To: Cantino et alii. 2007. "Towards a phylogenetic nomenclature of ''Tracheophyta''". ''Taxon'' 56(3):822-846. (see ''External links'' below). It is sometimes written as /Mesangiospermae even though this is not required by the PhyloCode. The "clademark" slash indicates that the term is intended as phylogenetically defined.

Description

In molecular phylogenetic

studies Study or studies may refer to: General * Education ** Higher education * Clinical trial * Experiment * Observational study * Research * Study skills, abilities and approaches applied to learning Other * Study (art), a drawing or series of d ...

, the mesangiosperms are always strongly supported as a monophyletic group.

, Pamela S. Soltis, Peter K. Endress, and

Mark W. Chase Mark Wayne Chase (born 1951) is a US-born British botanist. He is noted for work in plant classification and evolution, and one of the instigators of the Angiosperm Phylogeny Group-classification for flowering plants which is partly based on DNA ...

(2005). ''Phylogeny and Evolution of the Angiosperms''. Sinauer: Sunderland, MA There is no distinguishing characteristic which is found in all mature mesangiosperms but which is not found in any of the basal angiosperms. Nevertheless, the mesangiosperms are recognizable in the earliest stage of embryonic development.William E. Friedman and Kirsten C. Ryerson (2009). "Reconstructing the ancestral female gametophyte of angiosperms: Insights from Amborella and other ancient lineages of flowering plants". ''American Journal of Botany'' 96(1):129-143. The

ovule In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: the '' integument'', forming its outer layer, the ''nucellus'' (or remnant of the megasporangium), and the ...

contains a

megagametophyte A gametophyte () is one of the two alternating multicellular phases in the life cycles of plants and algae. It is a haploid multicellular organism that develops from a haploid spore that has one set of chromosomes. The gametophyte is the sex ...

, also known as an

embryo sac In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: the ''integument'', forming its outer layer, the ''nucellus'' (or remnant of the megasporangium), and the fem ...

, that is bipolar in structure and contains 8 cell nuclei. The

antipodal cell In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: the ''integument'', forming its outer layer, the ''nucellus'' (or remnant of the megasporangium), and the fem ...

s are persistent, and the endosperm is triploid.

History

The oldest known

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

s of flowering plants are fossil mesangiosperms from the

Hauterivian The Hauterivian is, in the geologic timescale, an age in the Early Cretaceous Epoch or a stage in the Lower Cretaceous Series. It spans the time between 132.9 ± 2 Ma and 129.4 ± 1.5 Ma (million years ago). The Hauterivian is preceded by th ...

stage of the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

period. Else Marie Friis, K. Raunsgaard Pedersen, and Peter R. Crane (2006). "Cretaceous angiosperm flowers: Innovation and evolution in plant reproduction". ''Palaeogeography, Palaeoclimatology, Palaeoecology''232(2-4):251-293.

Molecular clock The molecular clock is a figurative term for a technique that uses the mutation rate of biomolecules to deduce the time in prehistory when two or more life forms diverged. The biomolecular data used for such calculations are usually nucleo ...

comparisons of DNA sequences indicate that the mesangiosperms originated between 140 and 150 Mya (million years ago) near the beginning of the Cretaceous period.T. Jonathan Davies, Timothy G. Barraclough,

, Pamela S. Soltis,

, and Vincent Savolainen (2004). "Darwin's abominable mystery: Insights from a supertree of the angiosperms". ''Proceedings of the National Academy of Sciences'' 101(7):1904-1909. This was about 25 Ma (million years) after the origin of the angiosperms in the mid-

Jurassic The Jurassic ( ) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The Jurassic constitutes the middle period of ...

.Michael J. Moore, Charles D. Bell, Pamela S. Soltis, and

(2007). "Using plastid genome-scale data to resolve enigmatic relationships among basal angiosperms". ''Proceedings of the National Academy of Sciences'' 104(49):19363-19368. By 135Mya, the mesangiosperms had radiated into 5 groups:

Magnoliids Magnoliids (or Magnoliidae or Magnolianae) are a clade of flowering plants. With more than 10,000 species, including magnolias, nutmeg, bay laurel, cinnamon, avocado, black pepper, tulip tree and many others, it is the third-largest group of a ...

, Monocots, Ceratophyllales, and

Eudicots The eudicots, Eudicotidae, or eudicotyledons are a clade of flowering plants mainly characterized by having two seed leaves upon germination. The term derives from Dicotyledons. Traditionally they were called tricolpates or non-magnoliid dicot ...

. The radiation into 5 groups probably occurred in about 4 million years. Because the interval of this radiation (about 4 million years) is short in proportion to its age (about 145 million years), it had long appeared that the 5 groups of mesangiosperms had arisen simultaneously. The mesangiosperms were shown as an unresolved pentatomy in phylogenetic trees. In 2007, two studies attempted to

resolve Resolve may refer to: * ''Resolve'' (Lagwagon album) * ''Resolve'' (Last Tuesday album) * "Resolve" (song), by the Foo Fighters *''The Resolve'', a 1915 American silent short drama film * "Resolve" (''One Tree Hill'' episode) *''Resolve'', a Briti ...

the

phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups ...

relationships among these 5 groups by comparing large portions of their chloroplast genomes.Robert K. Jansen, Zhengqiu Cai, Linda A. Raubeson, Henry Daniell, Claude W. dePamphilis, James Leebens-Mack, Kai F. Müller, Mary Guisinger-Bellian, Rosemarie C. Haberle, Anne K. Hansen, Timothy W. Chumley, Seung-Bum Lee, Rhiannon Peery, Joel R. McNeal, Jennifer V. Kuehl, and Jeffrey L. Boore (2007). "Analysis of 81 genes from 64 plastid genomes resolves relationships in angiosperms and identifies genome-scale evolutionary patterns" ''Proceedings of the National Academy of Sciences'' 104(49):19369-19374 These studies agreed on the most likely phylogeny for the mesangiosperms. In this phylogeny, the monocots are sister to the clade eratophyllales + eudicots However, this result is not strongly supported. The approximately unbiased topology

test Test(s), testing, or TEST may refer to: * Test (assessment), an educational assessment intended to measure the respondents' knowledge or other abilities Arts and entertainment * ''Test'' (2013 film), an American film * ''Test'' (2014 film), ...

showed that some of the other possible positions of the monocots had more than 5% probability of being correct. The major weakness of these 2 studies was the small number of species whose DNA was being used in the phylogenetic analysis, 45 in one study and 64 in the other. This was unavoidable, because complete chloroplast genome sequences are known for only a few plants.

References

Bibliography

* * *

External links

Angiosperm Phylogeny
a
Missouri Botanical Garden

Electronic Supplement to Cantino et alii

Divergence Times
T. Jonathan Davies et alii. (2004). ''PNAS'' 101(7):1904-1909.

In
Montreal genomics
{{Taxonbar, from=Q2710933 Angiosperms Plant unranked clades