Genetic diversity of an endangered palm in forest and open grassland landscapes: informing seed collection and conservation of Butia eriospatha

The Atlantic Forest is a biodiversity hotspot facing severe habitat loss and fragmentation, with most of its remnants experiencing biomass and biodiversity declines. Butia eriospatha , a vulnerable palm species endemic to this biome, is threatened with extinction by habitat degradation, illegal poaching, and lack of regeneration. Despite its ecological and cultural importance, genetic studies have focused only on grassland populations, leaving the rare forest populations unexplored. Here, we compared genetic diversity aspects between a forest (FOR) and an open grassland (GRA) B. eriospatha populations, aiming to provide seed collection guidelines and further expand the knowledge on genetic conservation of this important species. We assessed genetic diversity, mating system, spatial genetic structure (SGS), and spatial pattern for GRA and FOR populations, by sampling mature and seedling individuals. Both populations exhibited moderate genetic diversity (\(\:{\widehat{H}}_{E}\) = 0.429–0.445), with no significant fixation, but significant genetic differentiation (\(\:{\widehat{F}}_{ST}\) = 2–3%) between them. Allogamy predominated in both populations, with outcrossing rates not different from unity, although FOR displayed a small proportion of mating among relatives. SGS was weak but extended over larger distances in FOR (up to 60 m) compared to GRA (up to 30 m), suggesting differences in mortality dynamics. For long-term conservation (\(\:{N}_{e}\) = 500) and to maximize genetic diversity, seeds should be collected from 132 up to 139 seed-trees, respecting SGS distances. Our findings highlight the need to conserve both grassland and forest populations to safeguard the B. eriospatha genetic diversity.