AOBPreview originally published online on January 5, 2004
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Annals of Botany 93: 201-209, 2004
© 2004 Annals of Botany Company
Population Genetic Structure of Titanotrichum oldhamii (Gesneriaceae), a Subtropical Bulbiliferous Plant with Mixed Sexual and Asexual Reproduction
1 Royal Botanic Garden, 20A Inverleith Row, Edinburgh EH3 5LR, UK, 2 Institute of Cell and Molecular Biology, University of Edinburgh, Edinburgh EH9 3JH, UK and 3 Botanical Garden and Centre for Plant Research, University of British Columbia, Vancouver, Canada V6T 2TL
* For correspondence. Fax +1-604-822-2016, e-mail botwang{at}ntu.edu.tw
Received: 7 April 2003;; Returned for revision: 29 August 2003; Accepted: 4 November 2003 Published electronically: 5 January 2004
• Background and Aims Titanotrichum oldhamii is a monotypic genus distributed in Taiwan, adjacent regions of China and the Ryukyu Isands of Japan. Its conservation status is vulnerable as most populations are small and widely scattered. Titanotrichum has a mixed system of reproduction with vegetative bulbils and seeds. The aim of this study was to understand the population genetic structure of Titanotrichum in relation to its specific reproductive behaviour and to determine possible implications for conservation strategies.
• Methods After an extensive inventory of most wild populations of Titanotrichum in East Asia, samples from 25 populations within its major distribution were carried out utilizing RAPD and inter-SSR molecular fingerprinting analysis.
• Key Results The findings support the conclusion that many populations reproduce predominantly asexually but that some genetic variation still exists within populations. However, significant amounts of variation exist between populations, perhaps reflecting population differentiation by drift. This partitioning of genetic diversity indicates that the level of inter-population gene exchange is extremely low. These findings are consistent with field observations of very limited seed production. The Chinese populations are similar to those of Northern Taiwan, while the Ryukyu populations fall within the range of variation of the north-central Taiwan populations. The Taiwanese populations are relatively variable and differentiation between north, east and south Taiwan is evident.
• Conclusions The distribution of Titanotrichum seems to be consistent with a former land connection between China, Taiwan and the Ryukyu Islands at a glacial maximum during the Quaternary, followed by progressive fragmentation of the populations. North-central Taiwan is the centre of genetic diversity, possibly due to the proximity of the former land bridge between the regions, together with the variety of suitable habitats in north Taiwan. The significance of these findings for conservation is discussed.
Key words: Facultative vegetative apomixis, sea-level change, Pleistocene biogeography, bulbil, vivipary, propagules, clonal plant.
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