Rivers of tropical islands formed by vol- canic eruptions experience unpredictable and heavy rainfall and are characterised by irregular topogra- phy. During the 2019 and 2020 low-water season, we investigated the responses of benthic macroinver- tebrate assemblages to variations in local environ- mental conditions in four rivers located in areas of different rainfall intensity. We found that changes in local environmental conditions associated with lower rainfall intensity reduced abundance and taxonomic richness and modified taxonomic composition but did not impact the balance of functional feeding groups of macroinvertebrate communities amongst streams, except for piercer herbivores. Heterotrophy associated with substrate instability and autotrophy with a more stable substrate co-occurred in semi-arid climate riv- ers. In contrast, a change from heterotrophy upstream to autotrophy and substrate stability downstream was apparent in the two humid rivers studied. Sur- rogates of stream ecosystem function revealed a very low ratio of coarse to fine particulate organic mat- ter related to the quasi-absence of shredders in these streams and suggested a low allochthonous input con- tribution, which could be the result of the 5% decline in forest cover over the two past decades.