Influence of past climate changes and human-mediated introduction on patterns of genetic diversity distribution of the Papuan nutmeg (Myristica argentea) Warb.

Understanding the distribution of genetic diversity of endemic food tree species holds significant importance for conservation planning and the formulation of effective management strategies. Natural and anthropogenic factors can influence species geographic range and distribution of genetic diversity. Here, we tested the relative influence of barriers to gene flow (rivers, mountains and past climate change) and recent human activities on the evolutionary history of an endemic species from Fakfak district, Papua Island, Myristica argentea Warb (Myristicaceae), better known as Papuan nutmeg. Myristica argentea is a spice tree species used by local populations since centuries/millennia. The species has been introduced in other locations from the region. Fourteen microsatellite markers (nSSRs), whole chloroplast (cp) genome, and nuclear-targeted sequence genes (nrDNA sequence) were used to characterize the genetic diversity, population structure, and demographic history of the species across its distribution range (native and introduced populations). We found that native populations of the species in Fakfak present higher levels of genetic diversity than introduced populations. We further detected the presence of a moderate genetic structure (FST = 0.143), and the presence of three intraspecific genetic clusters. Additionally, our findings indicate that population fragmentation within the native range of the species in Fakfak, may have been influenced by the presence of riparian networks, mountain ranges and by Pleistocene climatic fluctuations. Our results suggest that all introduced populations were sourced mainly from the native population of Raduria, in the South of Fakfak region. Given the population genetic variation across the ranges of Papuan nutmeg, management plans should not treat them as single populations, but rather consider the broader genetic diversity within its range.