Abstract
<title>Abstract</title> <p> <italic>Acrocomia aculeata</italic> is an emerging multipurpose oil palm with high potential for food, industrial, and bioenergy applications; however, limited information on the phenotypic and biochemical variation in Mesoamerican germplasm constrains its domestication and utilization. In this study, the fruit morphometrics, biomass partitioning, oil content, and fatty acid composition of the mesocarp and kernel of fruits collected from eight sites in Costa Rica were evaluated. Significant variation was observed among the sites for all the evaluated traits. Abangares and Turrubares showed the highest fruit mass and high biomass values, whereas Nicoya and Cuajiniquil presented lower values for several morphometric and biomass traits. The mesocarp oil content ranged from 11.23% to 35.97%, with the highest value recorded in Paso Real, while the kernel oil content ranged from 38.5% to 55.6%, with Turrubares showing the greatest accumulation. Fatty acid profiles differed markedly between tissues: mesocarp oil was dominated by oleic acid (55–64%), whereas kernel oil was characterized by high lauric acid content (27–35%). Principal component analyses revealed distinct patterns among the sites in terms of fruit size, biomass allocation, oil content, and fatty acid composition. These results demonstrate substantial phenotypic and biochemical diversity within the Costa Rican <italic>A. aculeata</italic> germplasm and suggest that different oil allocation patterns occur between mesocarp and kernel. This variability provides a valuable basis for germplasm selection, conservation, and breeding aimed at developing locally adapted, multipurpose production systems. </p>