Potential geographic distributions of endangered Opisthopappus Shih in response to environmental changes

Environmental changes could dramatically influence the distribution area and niche of organisms. Taihang Mountains contain numerous endemic species, regarded as a center of distribution and diversity for many plant genera. It is necessary that having more comprehensive studies of test climate effects on species in this area. Opisthopappus (containing two species Opisthopappus taihangensis and Opisthopappus longilobus) is an endangered and endemic genus in the Taihang Mountains. Predicting the suitable potential distribution, exploring the niche difference between two species and determining the important environmental factors are very critical for the sustainable utilization and scientific conservation. In this study, the distribution areas of both two species decreased drastically from the LIG to LGM period. Main refugia might have been in the centre of the Taihang Mountains. Compared LGM, the distribution ranges expanded in the Mid-Holocene period whether O. longilobus or O. taihangensis, and that generally similar to the present distribution areas of two species. From 2050 to 2070, the predicted distribution area greatly increased for both two species. Moreover, O. longilobus migrated toward south and east, while O. taihangensis moved toward west. Among all 37 environmental variables, fourteen variables (bio2, bio3, bio4, bio8, bio11, bio13, bio15, elev, T_CaCO3, T_GRAVEL, T_OC, T_SAND, T_SILT, T_TEB) were the most important factors influencing on the distribution of Opisthopappus. O. taihangensis and O. longilobus presented a significant niche differentiation, and this change occurred gradually with the passage of time. These would provide some clues for the management and conservation for O. taihangensis and O. longilobus.

Methods
The environmental factors were extracted with ARCGIS software.