Habitat heterogeneity drives the community assembly of Caridina spp. in Lake Poso, Sulawesi, with implications for lake conservation

Abstract Ancient lakes are among the most exceptional freshwater ecosystems on Earth, characterized by long-term isolation and high levels of species endemism. Investigating how environmental filtering influences species coexistence is vital for decoding community assembly in freshwater ecosystems, including ancient lakes. Lake Poso is one of the ancient lakes in Southeast Asia that contains a species flock (N = 11) of the genus Caridina, the result of adaptive radiation. Here, we integrated occurrence and environmental data from lake-wide sampling for endemic freshwater shrimps of the genus Caridina across Lake Poso, Indonesia, using Hierarchical Modeling of Species Communities (HMSC) and spatial prioritization. This study aimed to (i) estimate the species relative abundance and distribution, (ii) assess how environmental filtering drives their community assembly, (iii) evaluate lineage-specific responses to these variables, and (iv) identify critical conservation areas under anthropogenic pressure. A total of 32 sites have been surveyed across the northern, western, eastern, and southern shorelines of Lake Poso. The eight lacustrine species exhibited marked variation in mean and total abundance, indicating the presence of both generalist and specialist species. Microhabitat acted as a primary abiotic filter in explaining Caridina spp. distribution. Notably, specific habitats strongly filtered species based on chelae morphology as a functional trait. Spatial prioritization demonstrated that areas of high habitat suitability frequently coincide with intense human disturbance. Our results highlight the critical role of microhabitat heterogeneity in maintaining the occurrence of various endemic species of the genus Caridina. This study establishes a predictive framework for integrating endemic communities into conservation planning for tropical ancient lakes facing accelerating anthropogenic threats.