Retracing the center of origin and evolutionary history of nutmeg
Myristica fragrans, an emblematic spice tree species
Abstract
The identification of cultivated plant centers of origin is of growing
interest since the pioneering work of Nikolaï Vavilov. Cultivated
species generally show a high level of genetic diversity in their center
of origin, thus identifying these areas would have important
implications for the conservation and sustainable management of their
genetic resources. We aim to identify the center of origin and to infer
recent evolutionary history of one of the most emblematic spice tree
species ¬¬– nutmeg (Myristica fragrans; Myristicaceae). The species is
thought to originate from the Banda islands (Southern Moluccas
archipelago, Indonesia), but this has never been confirmed. We
characterized the genetic diversity of this species across the Moluccas
archipelago using recently developed nuclear microsatellites markers and
whole plastid genome sequences. We found two main intra-specific genetic
clusters: one in South Moluccas (Banda and Ambon islands) and another in
North Moluccas (Ternate, Tidore and Bacan islands). The latter cluster
showed higher genetic diversity than the South Moluccas cluster. We then
inferred the demographic history of nutmeg and evaluated different
evolutionary scenarios using Approximate Bayesian Computation (ABC)
analyses. Populations from South Moluccas show patterns of a recent
bottleneck, whereas North Molucca populations did not. Moreover, South
Moluccas populations are inferred as ancestral, with subsequent
population migration to the North Moluccas during the late Pleistocene
to early Holocene period. These results have strong implications for
conservation strategies of nutmeg.