Hotspot speciation

A study of Gladiolus carinatus in South Africa has provided insights into the process of speciation in biodiversity hotspots.

15 Jul 2011

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Gladiolus carinatus flower

Gladiolus carinatus (Image: John Manning).

There has been much debate over the origin of species diversity in biodiversity hotspots, particularly the rate of speciation over extinction and the geographic mode of speciation. In a new study, researchers have looked at speciation in the Gladiolus carinatus species complex (Iridaceae), which exhibits varying degrees of sympatry, in the biodiversity hotspot of the Cape Floristic Region in southern Africa.

They investigated the mechanisms involved in population and species differentiation through a combination of ecological and genomic approaches. Lineages were estimated to have diverged after the establishment of available habitat in the Cape littoral plain. Shifts in flowering time and morphology have developed to varying degrees over the last 0.3–1.4 million years. An amplified fragment length polymorphism genome scan revealed signatures of divergent and balancing selection, although half of the loci consistently behaved neutrally. Divergent species outliers (1%) and floral morph outliers (3%) represent a small proportion of the genome, but these loci produced clear genetic clusters of species and significant associations with floral traits.

These results indicate that the G. carinatus complex represents a continuum of recent speciation, providing further evidence for ecological adaptation in the face of gene flow. Mol. Ecol. 19, 4765 (2010).

Item from Prof. Vincent Savolainen (Professor of Organismic Biology, Imperial College London, & Research Fellow, Royal Botanic Gardens, Kew)
Originally published in Kew Scientist, issue 39

Article reference:

Rymer, P.D., Manning, J.C., Goldblatt, P., Powell, M.P. & Savolainen, V. (2010). Evidence of recent and continuous speciation in a biodiversity hotspot: A population genetic approach in southern African gladioli (Gladiolus; Iridaceae). Molecular Ecology 19(21): 4765-4782.

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