Urticales is an

order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (). The term angiosperm is derived from the Ancient Greek, Greek words (; 'container, vessel') and (; 'seed'), meaning that the seeds are enclosed with ...

s. Before

molecular phylogenetics Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...

became an important part of

plant taxonomy Plant taxonomy is the science that finds, identifies, describes, classifies, and names plants. It is one of the main branches of taxonomy (the science that finds, describes, classifies, and names living things). Plant taxonomy is closely allied ...

, Urticales was recognized in many, perhaps even most,

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 is exp ...

of plant classification, with some variations in

circumscription Circumscription may refer to: * Circumscribed circle * Circumscription (logic) *Circumscription (taxonomy) * Circumscription theory, a theory about the origins of the political state in the history of human evolution proposed by the American anthr ...

. Among these is the

Cronquist system The Cronquist system is a list of systems of plant taxonomy, taxonomic classification system of angiosperms, flowering plants. It was developed by Arthur Cronquist in a series of monographs and texts, including ''The Evolution and Classification of ...

(1981), which placed the order in the subclass Hamamelidae , as comprising: * Barbeyaceae *

Cannabaceae Cannabaceae is a small family of flowering plants, known as the hemp family. As now circumscribed, the family includes about 170 species grouped in about 11 genera, including '' Cannabis'' (hemp), '' Humulus'' (hops) and '' Celtis'' (hackberri ...

* Cecropiaceae *

Moraceae Moraceae is a family of flowering plants comprising about 48 genera and over 1100 species, and is commonly known as the mulberry or fig family. Most are widespread in tropical and subtropical regions, less so in temperate climates; however, their ...

Ulmaceae The Ulmaceae () are a family (biology), family of flowering plants that includes the elms (genus ''Ulmus''), and the zelkovas (genus ''Zelkova''). Members of the family are widely distributed throughout the Temperate, north temperate zone, and ha ...

Urticaceae The Urticaceae are a family, the nettle family, of flowering plants. The family name comes from the genus ''Urtica''. The Urticaceae include a number of well-known and useful plants, including nettles in the genus ''Urtica'', ramie (''Boehmeria ...

In the

APG III system The APG III system of flowering plant classification is the third version of a modern, mostly molecular-based, system of plant taxonomy being developed by the Angiosperm Phylogeny Group (APG). Published in 2009, it was superseded in 2016 by a f ...

(2009), the plants belonging to this order, along with four other families, constitute the order

Rosales Rosales (, ) are an order of flowering plants. Peter F. Stevens (2001 onwards). "Rosales". At: Trees At: Angiosperm Phylogeny Website. At: Missouri Botanical Garden Website. (see ''External links'' below) Well-known members of Rosales include: ...

. Cecropiaceae is no longer recognized as separate from Urticaceae. The families Ulmaceae, Cannabaceae, Moraceae, and Urticaceae form a

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

that has strong statistical support in

phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

analyses of

DNA sequence A nucleic acid sequence is a succession of bases within the nucleotides forming alleles within a DNA (using GACT) or RNA (GACU) molecule. This succession is denoted by a series of a set of five different letters that indicate the order of the nu ...

s.Shu-dong Zhang, Douglas E. Soltis, Yang Yang, De-zhu Li, and Ting-shuang Yi. "Multi-gene analysis provides a well-supported phylogeny of Rosales". ''Molecular Phylogenetics and Evolution'' 60(1):21-28. This clade has been informally called the urticalean rosids.Kenneth J. Sytsma, Jeffery Morawetz, J. Chris Pires, Molly Nepokroeff, Elena Conti, Michelle Zjhra, Jocelyn C. Hall, and Mark W. Chase. (2002). Urticalean rosids: Circumscription, rosid ancestry, and phylogenetics based on ''rbcL'', ''trnL-F'', and ''ndhF'' sequences. ''

American Journal of Botany The ''American Journal of Botany'' is a monthly peer-reviewed scientific journal which covers all aspects of plant biology. It has been published by the Botanical Society of America since 1914. The journal has an impact factor of 3.038, as of 20 ...

'' 89(9): 1531-1546
PDF fulltext
/ref> Urticalean rosids refers to the relationships amongst several families of angiosperms, and now includes more than 2,500 species. The families are: *

Qiu Y.-L. M. W. Chase S. B. Hoot E. Conti P. R. Crane K. J. Sytsma C. R. Parks 1998. Phylogenetics of the Hamamelidae and their allies: parsimony analyses of nucleotide sequences of the plastid gene rbcL. International Journal of Plant Sciences 159: 891-905. The relationships within the "urticalean lineage" are now considered to be within the Rosales.APG (Angiosperm Phylogeny Group). 1998. An ordinal classification for the families of flowering plants. Annals of the Missouri Botanical Garden 85: 531-553. The Moraceae and Urticaceae account for approximately 90% of the diversity within the clade.Sytsma, Kenneth J., Jeffery Morawetz, J. Chris Pires, Molly Nepokroeff, Elena Conti, Michelle Zjra, Jocelyn C. Hall, and Mark W. Chase. 2001. Urticalean Rosids: Circumscription, Rosid Ancestry, and Phylogenetics Based on RbcL, TrnL-F, and NdhF Sequences. American Journal of Botany Analysis of DNA samples in ''rbcL'', ''trnL-F'', and ''ndhF'' plastid regions suggests that Urticalean rosids are derived out of a lineage including Barbeyaceae, Dirachmaceae,

Elaeagnaceae The Elaeagnaceae are a plant family, the oleaster family, of the order Rosales comprising small trees and shrubs, native to temperate regions of the Northern Hemisphere, south into tropical Asia and Australia. The family has about 60 species in ...

, and

Rhamnaceae The Rhamnaceae are a large Family (biology), family of flowering plants, mostly trees, shrubs, and some vines, commonly called the buckthorn family. Rhamnaceae is included in the order Rosales. The family contains about 55 genera and 950 specie ...

, with Rosaceae less closely related. The morphological and molecular characters which define "urticalean rosids" are: * A dense gray tomentum comprising curly unicellular trichomes on abaxial leaf surfaces Tobe H. and T. Takaso 1996. Trichome micromorphology in Celtidaceae and Ulmaceae (Urticales). Acta Phytotaxonomica et Geobotanica 47: 153–168. * A reduced stamen count to one whorl or lessJudd W. S. C. S. Campbell E. A. Kellogg P. F. Stevens 1999. Plant systematics: a phylogenetic approach. Sinauer Associates, Sunderland, Massachusetts, USA.Stevens P. F. 2001. Angiosperm phylogeny website, v. 2, August 2001. http://www.mobot.org/MOBOT/research/APweb/. * Presence of inconspicuous flowers with up to five stamens * Presence of two carpels * A unilocular ovary with single apical ovule * Urticoid teeth upon leaves * Developed prophyllar buds between paired inflorescences Urticalean families span a wide range of morphological features—deciduous or evergreen trees, vines, shrubs, annuals and some succulents. Leaves also vary though they tend to share brochidodromous or palmately pinnate venation, often associated with lobing or compounding in the leaf blade. Among Moraceae, Urticacae and Cecropiaceae, mucilage cells and latex production is common. However, Cannabaceae and Ulmaceae do not produce this material despite the presence of laticifers.

References

{{Authority control Historically recognized angiosperm orders