Senecio eboracensis

York radiate groundsel, Senecio eboracensis, is a hybrid species of ragwort from York, England. It was discovered in 1979 and formally described in 2003. It occurs in urban habitats, such as disturbed earth and pavement cracks.^[1]

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Evolution

This plant is a hybrid species whose parents are Oxford ragwort (S. squalidus) and common groundsel (S. vulgaris). Like S. vulgaris, it is self-compatible, although S. squalidus is not; however, it shows little or no natural crossing with its parent species, and is therefore reproductively isolated.^[2] It is thought to have resulted from a backcrossing of the F1 hybrid of its parents to S. vulgaris.^[1] S. vulgaris is native to Britain, while S. squalidus was introduced from Sicily in the early 1700s;^[1]; therefore, S. eboracensis has speciated from those two species within the last 300 years.

Other hybrids descended from the same two parents are known. Some are infertile, such as S. x baxteri. Other fertile hybrids are also known, including S. vulgaris var. hibernicus, now common in Britain, and the allohexaploid S. cambrensis, which according to molecular evidence probably originated independently at least three times in different locations.^[1] Morphological and genetic evidence support the status of S. eboracensis as separate from other known hybrids.^[1][2]

Description

York radiate groundsel is an annual up to 40 cm (16 in.) high, with petiolate leaves morphologically distinct from those of related species. Flowers occur as apical inflorescences with 3-7 florets.^[1]

References

1. ^ ^{a b c d e f} Abbot, R.J.; Lowe, A.J. (2003). "A new British species, Senecio eboracensis (Asteraceae), another hybrid derivative of S. vulgaris L. and S. squalidae L." (PDF). Watsonia 24: pp. 375-388. Retrieved on 2007-07-15.
2. ^ ^{a b} Lowe, A.J.; Abbott, R.J. (May). "Reproductive isolation of a new hybrid species, Senecio eboracensis Abbott & Lowe (Asteraceae)". Heredity 92 (5): pp. 386-395. Retrieved on 2007-07-15.