# Coryloideae

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**Coryloideae** is a [subfamily](/source/Subfamily) in the woody [angiosperm](/source/Angiosperm) family [Betulaceae](/source/Betulaceae), commonly known as the birch family, and consists of four [genera](/source/Genera) - *[Corylus](/source/Corylus)* L., *[Ostryopsis](/source/Ostryopsis)* Decne., *[Carpinus](/source/Carpinus)* L., and *[Ostrya](/source/Ostrya)* Scop. These [deciduous](/source/Deciduous) [trees](/source/Tree) and [shrubs](/source/Shrub) are primarily distributed in the [boreal](/source/Boreal_climate) and cool [temperate zones](/source/Temperate_zone) of the Northern Hemisphere, with the majority occurring in Asia, many occurring in North America and a few species occurring as far south as South America.[1] [Synapomorphies](/source/Synapomorphies) such reduced staminate flowers, advanced wood anatomy features, and the presence of [spermidines](/source/Spermidine) in pollen define the Coryloideae.[2]

While the division of the extant members of the Betulaceae into six genera is uncontroversial, the placement of these genera into higher taxonomic ranks and the level of these ranks are debated. Extensive studies on the basis of ribulose- 1,5-biphosphate carboxylase (*rbc*L) sequences, [internal transcribed spacer](/source/Internal_transcribed_spacer) (ITS) sequences, morphology, and various combined data sets support the dichotomy of the Betulaceae into two major clades.[2][3][4][5] A few authors have divided the genera into two families, the Betulaceae (*Alnus*, *Betula*) and Corylaceae (*Carpinus*, *Ostrya*, *Corylus*, *Ostryopsis*).[6][7] Many modern authors recognize two separate [clades](/source/Clades) within the family, either as [tribes](/source/Tribe_(biology)) Betuleae and Coryleae or subfamilies Betuloideae and Coryloideae. There has also been debate on the further division of the Coryloideae into two tribes: Coryleae (*Corylus*) and Carpineae (*Ostryopsis*, *Carpinus*, *Ostrya*).[2][8]

## Fossil record

Based on distribution patterns of fossil and extant representatives (*Corylus*, *Carpinus*, and *Ostrya*) across temperate latitudes of the Northern Hemisphere, the Betulaceae probably originated in the temperate zones of Laurasia during the Cretaceous.[2] The pollen record also suggests that the Betuloideae predate the Coryloideae. *Alnus* and *Betula* differentiated as early 80 Mya during the Santonian in the [Cretaceous](/source/Cretaceous).[8] The earliest pollen grains of the Coryloideae, belonging to *Corylus*, appeared 67 Mya during the [Maestrichtian](/source/Maestrichtian) in the [Paleocene](/source/Paleocene).[8] *Carpinus* and *Ostrya* appeared later, 60 Mya and 41 Mya respectively; *Ostryopsis* has not yet been confirmed by similar fossil remains.[8]

## Tribe Coryleae

*Corylus*, commonly known as the hazels, is the sole living genus in the tribe Coryleae, and considered the sister group to tribe Carpinieae. *Corylus* is placed as the [sister group](/source/Sister_group) to the remaining Coryloideae because it shares [plesiomorphic](/source/Plesiomorphic) character states with the Betuloideae such as bisexual [inflorescences](/source/Inflorescences), [staminate](/source/Staminate) flowers with a [perianth](/source/Perianth), a [haploid](/source/Haploid) chromosome number of 14, and nonoperculate pollen [apertures](/source/Aperture_(botany)) with thickened endexine.[2] The [monophyly](/source/Monophyly) of *Corylus* species is defined by several morphological synapomorphies, including the large animal-dispersed nuts, [hypogeal seed germination](/source/Hypogeal_germination), and filaments that are completely divided longitudinally.[2] The genus is recognized as having either two or three main divisions as [sections](/source/Section_(botany)) or [subgenera](/source/Subgenera), with sections often being divided into subsections. Some authors divide it into subgenera *Acanthochlamys*, *Phyllochlamys*, and *Siphonochlamys*. Others divide the genus into two sections (*Acanthochlamys* and *Corylus*) with section *Corylus* into three subsections (*Corylus*, *Colurnae*, and *Siphonochlamys*).[4]

## Tribe Carpinieae

Tribe Carpinieae, containing *Ostryopsis*–*Carpinus*–*Ostrya* is defined by staminate flowers without a perianth, operculate pollen apertures with endexine not thickening at apertural region, a base chromosome number of 8, and a plicate leaf vernation pattern.[2][8] Several characters, including [glabrous](/source/Glabrousness_(botany)) [receptacle](/source/Receptacle_(botany)) of staminate flowers, smooth nutlet surface, and secondary veins extending directly into leaf teeth, differentiate *Ostryopsis* from *Carpinus* and *Ostrya*.

*Ostryopsis* is often considered the sister group of *Carpinus* and *Ostrya*, but its [phylogenetic](/source/Phylogenetic) position is debated. A close relationship with *Corylus* is supported by wood anatomy characters and chloroplast gene sequences.[5] The placement of *Ostryopsis* as sister to the *Ostrya*-*Carpinus* clade is supported by a phylogenetic tree based on chloroplast DNA data but placement basal to *Corylus* is supported in an ITS-based tree.[5]

*Carpinus* is often considered sister to *Ostrya*. DNA sequences suggest that *Carpinus* might have differentiated from the extinct genus *[Palaeocarpinus](/source/Palaeocarpinus)*.[2] *Carpinus* is defined by several morphological characters including presence of pistillodes in the male florets, and leafy [bracts](/source/Bracts) subtending the flowers and fruits.[5] *Carpinus* is divided into two sections, *Distegocarpus* and *Carpinus*, based on floral bracts, [infructescences](/source/Infructescence), and scales. Section *Carpinus* is further divided into three subsections – *Carpinus*, *Monbeigianae* and *Polyneurae*. The monophyly of the genus is debatable. ITS data suggests the genus is paraphyletic while chloroplast DNA and nuclear 5S spacer data support it as monophyletic.[5] *Carpinus* may also be considered paraphyletic depending on the placement of *Ostrya*.

*Ostrya* has a close relationship with *Carpinus*, which is strongly supported by ITS and rbcL sequences and morphological and combined data from several studies.[2][5] Although both genera share similar inflorescences, pollen grains and vessels with simple perforations, they differ in leaf epidermal characters and their infructescence bracts, which are radially symmetrical and inflated bladder-like in *Ostrya* and are open and flat in *Carpinus*.[2]

While the close relationship of *Carpinus* and *Ostrya* is supported by data, the monophyly of the two genera has remained controversial. Some studies have nested *Ostrya* within *Carpinus* between sections *Carpinus* and *Distegocarpus* on the basis of ITS data or placed *Ostrya* as a basal grade to the *Carpinus* clade on the basis of chloroplast DNA data.[5]

## References

1. Stults, D. Z. & Axsmith, B. J. 2009. Betulaceae From The Pliocene And Pleistocene Of Southwest Alabama, Southeastern United States. *Review Of Palaeobotany And Palynology*, 155, 25-31. [doi:10.1016/j.revpalbo.2009.01.001](https://doi.org/10.1016/j.revpalbo.2009.01.001)

1. Chen, Z. D., Manchester, S. R. & Sun, H. Y. 1999. Phylogeny And Evolution Of The Betulaceae As Inferred From Dna Sequences, Morphology, And Paleobotany. *American Journal of Botany*, 86, 1168-1181. [doi:10.2307/2656981](https://doi.org/10.2307/2656981)

1. Bousquet, Strauss & Li 1992, p. 1082.

1. Whitcher, I. N. & Wen, J. 2001. Phylogeny And Biogeography Of Corylus (Betulaceae): Inferences From Its Sequences. *Systematic Botany*, 26, 283-298. ISSN 0363-6445

1. Yoo, K. O. & Wen, J. 2007. Phylogeny Of Carpinus And Subfamily Coryloideae (Betulaceae) Based On Chloroplast And Nuclear Ribosomal Sequence Data. *Plant Systematics And Evolution*, 267, 25-35. [doi:10.1007/s00606-007-0533-2](https://doi.org/10.1007/s00606-007-0533-2)

1. Hutchinson, John (1964). [*The genera of flowering plants (*Angiospermae*). Vol. 1: Dicotyledones*](https://archive.org/details/generaofflowerin0001hutc/page/26/mode/1up). Oxford: Clarendon. p. 27.

1. Dahlgren, R.M.T. (1980). "A revised system of classification of the angiosperms.". *[Botanical Journal of the Linnean Society](/source/Botanical_Journal_of_the_Linnean_Society)*. **80** (2): 96. [doi:10.1111/j.1095-8339.1980.tb01661.x](https://doi.org/10.1111/j.1095-8339.1980.tb01661.x)

1. Bousquet, Strauss & Li 1992.

## Sources

- Bousquet, Jean; Strauss, Steven H.; Li, Peng (1992). ["Complete Congruence Between Morphological And Rbcl-Based Molecular Phylogenies In Birches And Related Species (Betulaceae)"](https://academic.oup.com/mbe/article/9/6/1076/1073675). *Molecular Biology and Evolution*. **9** (6): 1076–1088. [doi:10.1093/oxfordjournals.molbev.a040779](https://doi.org/10.1093/oxfordjournals.molbev.a040779)

## External links

- [Glossary of botanical terms](/source/Glossary_of_botanical_terms)
- [Flora of North America: Betulaceae](http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=10101)
- [USDA PLANTS Database](https://plants.usda.gov/java/)

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Adapted from the Wikipedia article [Coryloideae](https://en.wikipedia.org/wiki/Coryloideae) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Coryloideae?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.