Environment Institute Leaders publications

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Browsing Environment Institute Leaders publications by Author "Abbott, R."

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    A new British species Senecio eboracensis (Asteraceae) another hybrid derivative of S. vulgaris L. and S. squalidus L.
    (Botanical Society of the British Isles, 2003) Lowe, A.; Abbott, R.
    A new species of Senecio from York, England, is described and named as Senecio eboracensis. Evidence is reviewed that this fully fertile, tetraploid species (2n = 40), which was first discovered in 1979, is a hybrid product of S. vulgaris (2n = 40) and S. squalidus (2n = 20), and is distinct from another tetraploid hybrid product, the stabilized introgressant, S. vulgaris var. hibernicus, and also from the hexaploid hybrid product, S. cambrensis. Other studies have shown that S. eboracensis is reproductively isolated from its parents due to a high level of selfing, phenological separation, sterility of products of back crosses to S. squalidus and reduced fertility of products of back-crosses to S. vulgaris. The morphological similarity of S. eboracensis to partially fertile, intermediate hybrid plants collected from other locations in the British Isles is discussed, and would indicate that it could arise polytopically following hybridisation between the two parent species. However, other such intermediate hybrid products do not appear to have persisted at their site of origin.
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    Evolution in action: Britain's newest plant species is an unparalleled opportunity to study evolution
    (Natural Environment Research Council, 2003) Lowe, A.; Abbott, R.
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    Origins, establishment and evolution of new polyploid species: Senecio cambrensis and S. eboracensis in the British Isles
    (Blackwell Publishing Ltd, 2004) Abbott, R.; Lowe, A.
    Two new polyploid species of Senecio have originated in the British Isles in recent times following hybridization between native S. vulgaris (2n = 40) and introduced S. squalidus (2n = 20). One of these is the allohexaploid S. cambrensis (2n = 60), the other is the recombinant tetraploid S. eboracensis (2n = 40). We review what is known about when and how each species originated, and their reproductive isolation from parents due to high selfing rates. We also review evidence that suggests S. cambrensis may have undergone rapid genome evolution since its origin, and comment on the risks of extinction to each species due to chance factors operating during the early establishment phase. The discovery of both species soon after their origin provides an unparalleled opportunity to examine two different but related forms of speciation following hybridization between the same parent species. Further detailed study of the ecology and genomics of S. cambrensis and S. eboracensis will help improve our understanding of the process of polyploid speciation in plants. © 2004 The Linnean Society of London, Biological Journal of the Linnean Society.
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    Reproductive isolation of a new hybrid species Senecio eboracensis Abbott & Lowe (Asteraceae)
    (Nature Publishing Group, 2004) Lowe, A.; Abbott, R.
    The nature and extent of reproductive isolation was examined between a new self-compatible hybrid species Senecio eboracensis (2n=40) and its parents, self-incompatible S. squalidus (2n=20) and self-compatible S. vulgaris (2n=40). The triploid F(1) of S. eboracensis x S. squalidus exhibited very low seed set (x=0.63%), and F(2) and F(3) progeny were able to recover nominal levels of fertility (x=23.9 and 9.7%), while F(1) and F(2) offspring of S. eboracensis x S. vulgaris showed reduced seed set (x=63.8 and 58.8%). In both cases, evidence from previous work indicates that reduced fertility is associated with meiotic chromosome mispairing, and is a likely consequence of recombining both parental genomes within this new taxon. No hybrid offspring between S. eboracensis and S. squalidus were found in the wild, and only one such hybrid was recorded among 769 progeny produced by S. eboracensis surrounded by S. squalidus on an experimental plot. Natural crossing between S. eboracensis and S. vulgaris was recorded to be very low (between 0 and 1.46%) in the wild, but rose to 18.3% when individuals of S. eboracensis were surrounded by plants of S. vulgaris. It was concluded that strong breeding barriers exist between the new hybrid species and its two parents. Prezygotic isolation between S. eboracensis and S. vulgaris is likely to be largely due to both species reproducing by predominant self-fertilisation. However, differences recorded for germination, seedling survival, time of flowering and characters associated with pollinator attraction, plus significant clumping of juvenile and adult conspecifics in the wild, probably also contribute to reproductive isolation and ecological differentiation.