Elevational constraints and climatic buffering: comparison of Pierinae and Coliadinae across Taiwan Island and mainland China.

Different elevational gradients and anthropogenic pressures between island and mainland systems mediate discrete climatic sensitivities and distribution trends in butterfly lineages. We assess the comparative distributional changes of Pieridae (Pierinae and Coliadinae) on Taiwan Island and mainland China. Across Taiwan Island, the geographic range of Pieridae is mainly limited to lowlands due to the sharp decline in temperature with rising elevation. In mainland China, both reduced temperature and low precipitation at upper elevations shape Pieridae's spatial pattern. Across Taiwan, both subfamilies showed positive associations with human disturbances at greater elevations, while Pierinae showed a positive relationship with thick vegetation cover at lower elevations. Throughout mainland China, Pieridae exhibited negative associations with human disturbances and vegetation density at higher elevations. According to the MaxEnt results, across Taiwan Island, elevation is mainly responsible (80.6%) for the distribution of Pierinae, while maximum temperature of warmest month (Bio5) is mainly influencing (53.7%) the distribution of Coliadinae. Initially Pierinae exhibited an increase in highly suitable regions across the three historical periods, followed by a decrease. Conversely, Coliadinae showed an initial contraction, followed by an expansion. Future global warming may result in a reduction of highly appropriate habitats for both subfamilies without significant evidence of upslope migration. Most Pieridae species are projected to undergo habitat contraction, resulting in decreased species diversity. These outcomes indicate stronger ecological constraints and higher vulnerability to Pieridae diversity in island systems, highlighting the necessity of implementing regional conservation strategies.