To understand the forces driving biodiversity in tropical rainforests, this study investigated the extent to which environmental gradients and terrain structure affect morphological and genomic variation in the Australian rainbowfish (*Melanotaenia splendida splendida*). Using an integrative riverscape genomics and morphometrics framework, the researchers found that while neutral genetic population structure was explained by restricted gene flow, environmental variables, particularly hydrological and thermal factors, significantly explained both genetic and body shape variation. Climate-associated genetic variation was linked to morphology, supporting the heritability of shape variation. The results suggest evolved functional differences among localities and highlight the importance of hydroclimate in early diversification. The study concludes that substantial evolutionary responses will be needed for tropical rainforest endemics to adapt to changing climates.

Katie Gates, Jonathan Sandoval-Castillo, Chris J. Brauer, Peter J. Unmack, Martin Laporte, Louis Bernatchez, Luciano B. Beheregaray