Taxonomy
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Phylogeny[edit]
The oldest fossils attributed to Carya are Cretaceous pollen grains from Mexico and New Mexico. Fossil and molecular data suggest the genus Carya may have diversified during the Miocene. Modern Carya first appeared in Oligocene strata 34 million years ago. Recent discoveries of Carya fruit fossils further support the hypothesis that the genus has long been a member of Eastern North American landscapes, however, its range has contracted, and Carya is no longer extant west of the Rocky Mountains.
Fossils of early hickory nuts show simpler, thinner shells than modern species, with the exception of pecans, suggesting that the trees gradually developed defenses to rodent seed predation.[citation needed] During this time, the genus had a distribution across the Northern Hemisphere, but the Pleistocene Ice Age, beginning 2 million years ago, obliterated it from Europe. In Anatolia, the genus appears to have disappeared only in the early Holocene, probably related to human disturbance. The distribution of Carya in North America also contracted, and it completely disappeared from the continent west of the Rocky Mountains. It is likely that the genus originated in North America, and later spread to Europe and Asia.
Subdivision[edit]
The genus Carya (not to be confused with Careya in the Lecythidaceae) is in the walnut family, Juglandaceae. In the APG system, this family is included in the order Fagales. Several species are known to hybridize, with around nine accepted, named hybrids.
Asian hickories[edit]
Carya sect. Sinocarya
Roasted Carya cathayensis (Chinese hickory)
Carya dabieshanensis M.C. Liu – Dabie Shan hickory (may be synonymous with C. cathayensis)
Carya cathayensis Sarg. – Chinese hickory
Carya hunanensis W.C.Cheng & R.H.Chang – Hunan hickory
Carya kweichowensis Kuang & A.M.Lu – Guizhou hickory
Carya luodianensis Yang, Y. B (2026)
Carya poilanei Leroy – Poilane's hickory
Carya sinensis Dode – Beaked hickory
Carya tonkinensis Lecomte – Vietnamese hickory
C. sinensis has sometimes been split out in a separate genus as Annamocarya sinensis, but not by Plants of the World Online, as genetic data support it being embedded within the other Asian Carya.
North American hickories[edit]
Carya sect. Carya – typical hickories
Nuts of Carya texana (black hickory)
Carya floridana Sarg. – scrub hickory
Carya glabra (Mill.) Sweet – pignut hickory, pignut, sweet pignut, coast pignut hickory, smoothbark hickory, swamp hickory, broom hickory
Carya laciniosa (Mill.) K.Koch – shellbark hickory, shagbark hickory, bigleaf shagbark hickory, kingnut, big shellbark, bottom shellbark, thick shellbark, western shellbark
Carya myristiciformis (F.Michx.) Nutt. – nutmeg hickory, swamp hickory, bitter water hickory
Carya ovalis (Wangenh.) Sarg. – red hickory, spicebark hickory, sweet pignut hickory (treated as a variety of C. glabra by Flora N. Amer. and Plants of the World Online)
Carya ovata (Mill.) K.Koch – shagbark hickory
C. o. var. ovata – northern shagbark hickory
C. o. var. australis – southern shagbark hickory, Carolina hickory (syn. C. carolinae-septentrionalis)
Carya pallida (Ashe) Engl. & Graebn. – sand hickory
Carya texana Buckley – black hickory
Carya tomentosa (Poir.) Nutt. – mockernut hickory (syn. C. alba)
†Carya washingtonensis Manchester – Miocene of Kittitas County, Washington
Carya sect. Apocarya – pecans
Foliage of Carya cordiformis (bitternut hickory)
Carya aquatica (F.Michx.) Nutt. – bitter pecan or water hickory
Carya cordiformis (Wangenh.) K.Koch – bitternut hickory
Carya illinoinensis (Wangenh.) K.Koch – pecan
Carya palmeri W.E. Manning – Mexican hickory