<p>Understanding how closely related species coexist is key to explaining global biodiversity patterns. We hypothesized that Blue Tilapia diverged in certain biological traits and trophic niche utilization in syntopy versus allotopy with Redbelly Tilapia in the arid Draa basin, Morocco. These two relic tilapia species are ecologically important in the arid Draa basin, where environmental stressors threaten their persistence, making understanding their coexistence critical for conservation. We estimated body condition and growth parameters from body length-age data. Size and age at maturity, mortality, and longevity were derived from growth parameters. Stomach contents were analyzed to determine and compare diet composition. Lastly, morphological characters were analyzed across populations. Allotopic Blue Tilapia exhibited superior body condition, larger asymptotic size, faster growth, and earlier maturation than their syntopic conspecifics. Redbelly Tilapia displayed lower body condition but demonstrated rapid growth and early maturation, suggesting an adaptive strategy suited to the stressed environment. Despite high trophic niche overlap and generalist diets dominated by macrophytes and detritus, allotopic Blue Tilapia consumed more phytoplankton, while Redbelly Tilapia uniquely incorporated insects. The morphological divergence in the syntopic Blue Tilapia, particularly in traits such as jaw length and body depth, suggested the development of adaptive traits that may have facilitated resource partitioning and reduced interspecific competition. These findings align with niche theory, demonstrating that coexistence is mediated by fine-scale trophic specialization, life-history plasticity, and morphological adaptations.</p>