Integrating range shifts under climate change into the synchronous conservation of a critically endangered gibbon and its habitat trees

Primates rely heavily on habitat trees (foraging and night lodging trees) for growth and reproduction, yet primates' and their habitat trees' spatial ranges often shift with environmental changes. Therefore, endangered primates are severely threatened by habitat degradation and climate change. Hainan gibbon (Nomascus hainanus) is the world's most endangered primate. Using 18 years (2000 to 2018) of gibbon activity observations and data from 186 plant plots within a tropical nature reserve, we assessed the suitable distributions of gibbon and its 95 associated habitat trees using MaxEnt model, incorporating climate, topography, anthropogenic disturbance, and soil (excluded for gibbon) as predictors. Priority conservation areas were delineated by integrating habitat tree hotspots with suitable gibbon ranges. We also used Partial Least Squares Path Modeling to assess the direct and indirect effects of key factors shaping their distributions. Results showed that the gibbon occur in the central and eastern reserve, while habitat trees are mainly in the central region, both occur between 500 and 1400 m elevation. Climate change led to an upward shift and contraction in gibbon and habitat trees, accompanied by fragmentation. Spatial overlap between gibbon distributions and habitat tree hotspots was high (80.12 %–100 %). Priority conservation, primarily shaped by temperature and precipitation, were projected to become increasingly concentrated around two high-elevation hilltops. From current to future, climate remains the dominant driver of gibbon distribution, while the influence of habitat trees increases initially before declining. Our findings highlight the importance of integrating climate and habitat factors into conservation planning for endangered species.