Myristica swamps are one of the ancient and ecologically significant forested wetland ecosystems of the Western Ghats in India. These habitats have retained much of their original species composition and are home to paleoendemic species – ancient evolutionary remnants that now survive in isolated and in highly specialised ecological niches. Often termed as “living fossils,” these swamps are dominated by species of the Myristicaceae family, whose evolutionary lineage dates back approximately 140 million years. They serve as vital resources for studying long-term evolutionary processes. Many of these swamps are also considered sacred and protected as sacred groves, reflecting a blend of ecological and cultural heritage. However, many of these landscapes have experienced ecological degradation and cultural erosion due to colonial and post-colonial forest policies.

Despite their importance, Myristica swamps are vulnerable to habitat fragmentation, and there is limited genetic research, especially with swamp-obligate species such as Myristica fatua and Gymnacranthera canarica. In particular, Gymnacranthera canarica, a key species in these swamps, has been studied primarily for seed germination, pharmacological use, phenology, and taxonomy – but not for its genetic diversity or population structure. This lack of genetic insight limits our understanding of the species’ resilience and evolutionary history.

To fill this research gap, the present study aimed to: (1) assess the haplotype diversity of G. canarica in six populations across two river basins in the central Western Ghats; (2) construct a global phylogenetic tree of Myristicaceae species; and (3) study the evolutionary history of fruit and seed morphology in the family. These objectives were aimed at clarifying the population dynamics of G. canarica and contributing to a deeper understanding of the evolutionary pathways within Myristicaceae.

The study revealed a single shared haplotype between the Aghanashini and Sharavathi river basins, despite geographic separation. This lack of chloroplast diversity is likely due to seed-mediated gene flow by frugivorous birds like hornbills, which can disperse seeds over long distances. Although G. canarica is a swamp specialist with typically low genetic diversity and limited population size, its persistence may be due to its strong adaptation to niche habitats. However, pressures from habitat loss and commercial harvesting have made it vulnerable.

The study also observed low resolution in chloroplast markers, as chloroplast DNA evolves slowly due to its conserved and uniparentally inherited nature. Differences in the psbA-trnH region suggest possible local divergence, but overall variation remains minimal. Phylogenetic analyses showed both expected and unexpected relationships within Myristicaceae. For example, genera like Knema and Myristica clustered together based on shared biogeographic history. However, some Asian-African clades appeared inconsistently with previous studies, likely due to limited taxon sampling and the use of only two chloroplast regions.

Fruit-frugivore interactions were highlighted as key evolutionary drivers influencing the diversification of fruit morphology, aril characteristics, and dehiscence patterns in Myristicaceae. The fruits, with their bright, lacerated arils, attract visual frugivores like birds and primates, facilitating seed dispersal. Evolutionary traits such as aril morphology and fruit dehiscence vary across regions and disperser types. For instance, Otoba fruits evolved traits attractive to nocturnal bats, while Malagasy genera, due to a lack of visual frugivores, produce large, indehiscent fruits. These patterns reflect deep evolutionary relationships shaped by dispersal ecology.