e-journal

Evolutionary diversification and geographical isolation in Dubautia laxa (Asteraceae), a widespread member of the Hawaiian silversword alliance

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Background and Aims The Hawaiian silversword alliance (Asteraceae) is one the best examples of a plant adaptive radiation, exhibiting extensive morphological and ecological diversity. No research within this group has addressed the role of geographical isolation, independent of ecological adaptation, in contributing to taxonomic diversity. The aims of this study were to examine genetic differentiation among subspecies of Dubautia laxa (Asteraceae) to determine if allopatric or sympatric populations and subspecies form distinct genetic clusters to understand better the role of geography in diversification within the alliance.
Methods Dubautia laxa is a widespread member of the Hawaiian silversword alliance, occurring on four of the five major islands of the Hawaiian archipelago, with four subspecies recognized on the basis of morphological, ecological and geographical variation. Nuclear microsatellites and plastid DNA sequence data were examined.
Data were analysed using maximum-likelihood and Bayesian phylogenetic methodologies to identify unique
evolutionary lineages.
Key Results Plastid DNA sequence data resolved two highly divergent lineages, recognized as the Laxa and
Hirsuta groups, that are more similar to other members of the Hawaiian silversword alliance than they are to each other. The Laxa group is basal to the young island species of Dubautia, whereas the Hirsuta group
forms a clade with the old island lineages of Dubautia and with Argyroxiphium. The divergence between the
plastid groups is supported by Bayesian microsatellite clustering analyses, but the degree of nuclear differentiation is not as great. Clear genetic differentiation is only observed between allopatric populations, both within and among islands.
Conclusions These results indicate that geographical separation has aided diversification in D. laxa, whereas ecologically associated morphological differences are not associated with neutral genetic differentiation. This suggests that, despite the stunning ecological adaptation observed, geography has also played an important role in the Hawaiian silversword alliance plant adaptive radiation.
Key words: Dubautia laxa, Hawaiian silversword alliance, infraspecific divergence, subspecies, speciation,
geographical divergence, microsatellites, plastid DNA, chloroplast DNA.

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Informasi Detail

Judul Seri

Annals of Botany

No. Panggil

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Penerbit

: Oxford University Press on behalf of the Annals of Botany Company., 2011

Deskripsi Fisik

Annals of Botany 107: 357–370, 2011

Bahasa

English

ISBN/ISSN

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Klasifikasi

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Tipe Isi

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Tipe Media

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Tipe Pembawa

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Edisi

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Subjek

PERTANIAN.

Info Detail Spesifik

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Pernyataan Tanggungjawab

yuli/agus

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