Rubroshorea curtisii (Meranti Seraya) is a species in the Dipterocarpaceae family that is of ecological and economic signi8icance. The distribution of these species in Indonesia has been reported only in Sumatra, Singkep, and Lingga, and it is currently found in Batam Island, Riau Archipelago, Indonesia. The pressure of development on Batam has caused the forest to be fragmented into smaller parts and signi8icantly reduced the natural habitat of Rubroshorea curtisii. The objective of this research was to assess the synecology of Rubroshorea curtisii species to determine whether the fragmented forest landscape in Batam is an important biodiversity patch for Rubroshorea curtisii by analyzing its structure, composition, and abundance in the Sei Harapan and Bukit Tiban fragmented forests. The study used a vegetation analysis approach employing purposive sampling in 12 circular plots for each site where Rubroshorea curtisii grew naturally. In the Sei Harapan Fragmented Forest, the Important Value Index for the species was 138.01% (tree), 46.48% (pole), 23.38% (sapling), and 27.12% (seedling), while in the Bukit Tiban fragmented forest was 121.79% (tree), 26.67% (sapling), and 30.31% (seedling). At the pole stage, Calophyllum inophylloide had the highest Important Value Index (22.62%). Regarding the diversity index, all growth stages were considered high and medium, with 3,12 (seedling), 3.37 (sapling), 2.91 (pole), and 2,09 (tree) in the Sei Harapan fragmented forest, and 3,12 (seedling), 3.45 (sapling), and 3,44 (pole), 2.33 (tree). The evenness index is all categorized as high, with 0.94 (seedling), 0.94 (sapling), 0.93 (pole), and 0.72 (tree) in Sei Harapan fragmented forest and also categorized as high in Bukit Tiban fragmented forest with 0.91 (seedling), 0.93 (sapling), 0.94 (pole), and 0.72 (tree). The species richness index in the Sei Harapan fragmented forest is classi8ied as high with 6.62 (seedling), 8.06 (sapling), and 5.78 (pole), but at the tree level, it is classi8ied as medium with a value of 4.10. In the Bukit Tiban area, all life stages are categorized as having a high level of species richness, with 6.42 (seedling), 9.26 (sapling), 8.67 (pole), and 5.37 (tree). The study revealed that the fragmented forest on the highly industrialized island of Batam serves as a forest pocket that preserves valuable tropical biodiversity.
