蜜桃av

Ginkgo?is a??of non-flowering?. The scientific name is also used as the English name. The order to which it belongs,?, first appeared in the?,?270 million years ago, and?Ginkgo?is now the only living genus within the order. The rate of evolution within the genus has been slow, and almost all its species had become extinct by the end of the?. The sole surviving species,??is only found in the wild in China, but is cultivated around the world. The relationships between ginkgos and other groups of plants are not fully resolved.

Prehistory

The ginkgo (Ginkgo biloba) is a?, with fossils similar to the modern plant dating back to the?, 270?million years ago. The closest living relatives of the clade are the?,?which share with the extant?G.?biloba?the characteristic of??sperm. The ginkgo and cycad lineages are thought to have an extremely ancient divergence dating to the early?.?Fossils attributable to the genus?Ginkgo?with reproductive organs similar to the modern species first appeared in the?,?and the genus diversified and spread throughout??during the??and?. It declined in diversity as the Cretaceous progressed with the extinction of species such as?, and by the?, only a few?Ginkgo?species,??and?, remained in the Northern Hemisphere, while a markedly different (and poorly documented) form persisted in the?.^[]?At the end of the?,?Ginkgo?fossils disappeared from the fossil record everywhere except in a small area of central China, where the modern species survived. It is doubtful whether the Northern Hemisphere fossil species of?Ginkgo?can be reliably distinguished. Given the slow pace of evolution and morphological similarity between members of the genus, there may have been only one or two species existing in the Northern Hemisphere through the entirety of the?: present-day?G.?biloba?(including?G.?adiantoides) and??from the Palaeocene of?.

At least morphologically, G.?gardneri?and the 蜜桃av Hemisphere species are the only known post-Jurassic taxa that can be unequivocally recognised. The remainder may have been??or?. The implications would be that?G.?biloba?had occurred over an extremely wide range, had remarkable genetic flexibility and, though??genetically, never showed much?. While it may seem improbable that a species may exist as a contiguous entity for many millions of years, many of the ginkgo's life-history parameters fit. These are: extreme longevity; slow reproduction rate; (in Cenozoic and later times) a wide, apparently contiguous, but steadily contracting distribution coupled with, as far as can be demonstrated from the fossil record, extreme ecological conservatism (restriction to disturbed streamside environments).

Modern-day?G.?biloba?grows best in well-watered and drained environments,?and the extremely similar fossil?Ginkgo?favoured similar environments. The sediment records at the majority of fossil?Ginkgo?localities indicate it grew primarily in disturbed environments along streams and?.?Ginkgo?therefore presents an "ecological paradox" because, while it possesses some favourable traits for living in disturbed environments (clonal reproduction), many of its other life-history traits (slow growth, large seed size, late reproductive maturity) are the opposite of those exhibited by modern plants that thrive in disturbed settings.

Given the slow rate of evolution of the genus, it is possible that?Ginkgo?represents a pre-?strategy for survival in disturbed streamside environments.?Ginkgo?evolved in an era before flowering plants, when?,?, and??dominated disturbed streamside environments, forming a low, open, shrubby canopy. The large seeds of?Ginkgo?and its habit of "bolting"—growing to a height of 10 metres (33?ft) before elongating its side branches—may be adaptations to such an environment. Diversity in the genus?Ginkgo?dropped through the Cretaceous (along with that of ferns, cycads, and cycadeoids) at the same time the flowering plants were on the rise, which supports the notion that flowering plants, with their better adaptations to disturbance, displaced?Ginkgo?and its associates over time.

?from the earliest Permian of France, is one of the earliest fossils ascribed to the Ginkgophyta.?It had multiple-forked non-laminar leaves with cylindrical, thread-like ultimate divisions.??(early Permian-Cretaceous) had wedge-shaped leaves divided into narrow dichotomously-veined lobes, lacking distinct??(leaf stalks).?Baiera?(Triassic-Jurassic) had similar multiple-lobed leaves but with petioles.^:?743–756?

Phylogeny

As of February?2013,??have produced at least six different placements of?Ginkgo?relative to?,?,??and?. The two most common are that?Ginkgo?is a sister to a??composed of conifers and gnetophytes and that?Ginkgo?and cycads form a clade within the?. A 2013 study examined the reasons for the discrepant results and concluded that the best support was for the??of?Ginkgo?and cycads.

Etymology

The genus name is regarded as a misspelling of the??gin kyo?for the??銀杏 meaning "silver apricot",^[]?which is found in??literature such as?日用本草?(Daily Use?) (1329) and??本草纲目?published in 1578.

Despite its spelling, which is due to a complicated etymology including a transcription error, "ginkgo" is usually pronounced?, which has given rise to the common alternative spelling "gingko". The???is also documented in some dictionaries.

?first introduced the spelling?ginkgo?in his book?Amoenitatum Exoticarum. It is considered that he may have misspelled "Ginkyo" as "Ginkgo". This misspelling was included by??in his book?Mantissa plantarum II?and has become the name of the tree's genus.