Genetic diversity and population structure of an insular tree, Santalum austrocaledonicum in New Caledonian archipelago

Abstract

We present a study of the genetic diversity and structure of a tropical tree in an insular system. Santalum austrocaledonicum is endemic to the archipelago of New Caledonia and is exploited for oil extraction from heartwood. A total of 431 individuals over 17 populations were analysed for eight polymorphic microsatellite loci. The number of alleles per locus ranged from 3 to 33 and the observed heterozygosity per population ranged from 0.01 in Maré to 0.74 in Ile des Pins. The genetic diversity was lowest in the most recent islands, the Loyautés, and highest in the oldest island, Grande Terre, as well as the nearby small Ile des Pins. Significant departures from panmixia were observed for some loci-population combinations (per population F IS = 0 -0.03 on Grande-Terre and Ile des Pins, and 0 -0.67 on Loyautés). A strong genetic differentiation among all islands was observed ( F ST = 0.22), and the amount of differentiation increased with geographic distance in Iles Loyauté and in Grande Terre. At both population and island levels, island age and isolation seem to be the main factors influencing the amount of genetic diversity. In particular, populations from recent islands had large average F IS that could not be entirely explained by null alleles or a Wahlund effect. This result suggests that, at least in some populations, selfing occurred extensively. Conclusively, our results indicate a strong influence of insularity on the genetic diversity and structure of Santalum austrocaledonicum .

Comparative Molecular and Phytochemical Study of the Tree Species Santalum austrocaledonicum (Santalaceae) Distributed in the New‐Caledonian Archipelago

“…The results presented here on 157 individuals are concordant with those obtained with a larger sample and both nuclear and chloroplast microsatellites [44] [48]. They demonstrate that the genetic drift and the reduced migration between populations are the predominant forces acting on the genetic diversity within the natural range in New Caledonia.…”

“…In the present article, we used the same primers to genotype the 157 individuals. These trees constitute a sub-sample of the 431 individuals used in a previous molecular analyses [44] of the genetic diversity of S. austrocaledonicum.…”

“…As the region of Grande Terre, Ile des Pins, and Loyauté islands (Fig. 1) do not have the same origin, and have been shown to diverge for neutral markers [44], we investigated the occurrence of a regional effect in the observed chemical distributions. The regional effect was significant at the 0.05 level for eleven GC peaks among a total of 33: some 10 signals constituted less than 1.71% in the concrete, and (Z)-a-trans-bergamotol was found to be an important molecule.…”

Combining microsatellites, growth, and adaptive traits for managing in situ genetic resources ofEucalyptus urophylla

“…The low differentiation observed in the present study is unexpected in an insular system; such species generally exhibit a high F ST , because the presence of oceanic barriers restricts gene flow between populations (Bottin et al 2005). This apparent contradiction in the case of E. urophylla can be explained by a high migration rate compared with drift.…”

New Caledonia: a very old Darwinian island?

“…However, recent phylogenetic studies provide some insight into microendemism patterns and their causes. Microendemism appears primarily related to allopatric speciation in plants (Eibl et al 2001;Swenson et al 2001Swenson et al , 2007Bartish et al 2005;Bottin et al 2005;Tronchet et al 2005), insects (Desutter- Murienne et al 2005, in press a), land snails ( Trewick et al in press) and lizards (Bauer & Sadlier 2000;Bauer et al 2006;Smith et al 2007), even though some cases of sympatry and even syntopy have also been documented in diving beetles (Balke et al 2004(Balke et al , 2007b.…”