The tachibana orange (''Citrus tachibana,'' or ''Citrus reticulata tachibana'') is a variety of

mandarin orange The mandarin orange (''Citrus reticulata''), also known as the mandarin or mandarine, is a small citrus tree fruit. Treated as a distinct species of orange, it is usually eaten plain or in fruit salads. Tangerines are a group of orange-colou ...

, a

citrus ''Citrus'' is a genus of flowering trees and shrubs in the rue family, Rutaceae. Plants in the genus produce citrus fruits, including important crops such as oranges, lemons, grapefruits, pomelos, and limes. The genus ''Citrus'' is native to ...

fruit. They grow wild in the forests of Japan and are referred to in the poetry of the early Japanese and

Ryukyu Islands The , also known as the or the , are a chain of Japanese islands that stretch southwest from Kyushu to Taiwan: the Ōsumi, Tokara, Amami, Okinawa, and Sakishima Islands (further divided into the Miyako and Yaeyama Islands), with Yona ...

kingdoms. and Supplement The Tanaka System assigns them their own species, while the Swingle System places them in the same species with other

s. Genomic analysis has shown tachibana oranges to be a constellation of distinct natural

F1 hybrid An F1 hybrid (also known as filial 1 hybrid) is the first filial generation of offspring of distinctly different parental types. F1 hybrids are used in genetics, and in selective breeding, where the term F1 crossbreed may be used. The term is some ...

s that cross the pure Ryukyu Island mandarin '' C. ryukyuensis'' with mainland Asian '' C. reticulata'' that was itself a hybrid of northern and southern subspecies, but also contained some prior Ryukyu mandarin introgression. They lack the

pomelo The pomelo ( ), ''Citrus maxima'', is the largest citrus fruit from the family Rutaceae and the principal ancestor of the grapefruit. It is a natural, non-hybrid, citrus fruit, native to Southeast Asia. Similar in taste to a sweet grapefr ...

introgression found in the closely-related domesticated mandarin oranges of mainland Asia, though they have a mainland-mandarin-derived

transposable element A transposable element (TE, transposon, or jumping gene) is a nucleic acid sequence in DNA that can change its position within a genome, sometimes creating or reversing mutations and altering the cell's genetic identity and genome size. Transp ...

insertion that causes them to reproduce asexually by apomixis, unlike their sexually-reproducing Ryukyu mandarin parent. This distinctive island parent is estimated to have diverged from mainland Asian mandarins, probably arising before 2 million years ago near where its mandarin cousins would later be domesticated in the

Nanling Mountains The Nanling (), also known as the Wuling (), is a major mountain range in Southern China that separates the Pearl River Basin from the Yangtze Valley and serves as the dividing line between south and central subtropical zones. The main rang ...

of China, and likely spread to the islands over

land bridge In biogeography, a land bridge is an isthmus or wider land connection between otherwise separate areas, over which animals and plants are able to cross and colonize new lands. A land bridge can be created by marine regression, in which sea leve ...

s formed during

Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed in ...

glacial maxima, Rising sea levels provided the isolation that led to speciation, then either a subsequent fall in sea level or

oceanic dispersal Oceanic dispersal is a type of biological dispersal that occurs when terrestrial organisms transfer from one land mass to another by way of a sea crossing. Island hopping is the crossing of an ocean by a series of shorter journeys between isla ...

by rafting reestablished contact to allow for natural hybridization between the island and mainland mandarins between 40,000 and 200,000 years ago, giving rise to the tachibana oranges. The fruit is extremely bitter and thus nearly inedible.

References

tachibana The term has at least two different meanings, and has been used in several contexts. People * – a clan of ''kuge'' (court nobles) prominent in the Nara and Heian periods (710–1185) * – a clan of ''daimyō'' (feudal lords) prominent in the Mu ...

Fruits originating in East Asia Japanese fruit {{Rutaceae-stub