Integrating Host Plant Availability into Ensemble Models Reveals Divergent Responses of Three Endangered Papilionid Butterflies to Climate Change in China

Climate change is altering the potential distribution of many butterfly species, but climatic suitability alone may be insufficient to sustain the long-term viability of host-dependent butterflies. For papilionid butterflies, larval feeding and development depend on specific host plants; however, the extent to which host plant availability modifies projected suitable habitats under climate change remains unclear. Here, we first selected three threatened papilionids in China: Luehdorfia chinensis Leech, Teinopalpus imperialis Hope, and Troides aeacus C. & R. Felder (Lepidoptera: Papilionidae). Then we constructed two sets of ensemble distribution models: an environment-only model (Env-only) and a host-inclusive model (Env+Host), and compared the resulting projections for each species under current and future climate scenarios (the 2050s, 2070s, and 2090s under SSP1–2.6, SSP2–4.5, and SSP5–8.5). Landscape pattern metrics were further employed to assess changes in the spatial structure of suitable habitats. In the Env-only models, precipitation-related variables were identified as the primary factors constraining the potential distributions of all three species. After it was incorporated, host plant availability became the most important predictor for L. chinensis (41.54%) and T. aeacus (51.53%). In contrast, precipitation of the warmest quarter remained the dominant predictor for T. imperialis (36.00%). Compared with the Env-only models, the Env+Host models forecast smaller suitable habitats for all three species under all scenarios. T. imperialis exhibited the largest host-related contraction under SSP5–8.5 2090s (68.44%). Additionally, landscape pattern metrics indicated increased habitat fragmentation for L. chinensis and T. imperialis, but enhanced spatial continuity for T. aeacus. Overall, the three species have pronounced interspecific differences in their responses to the incorporation of host plant availability. These findings suggest that biotic factors should be incorporated into suitable habitat assessments for threatened papilionids in China. Accordingly, conservation strategies should be tailored to their host specificity, climate-driven distribution, and habitat requirements.