[Potential suitable area and niche shift of different ploidy kiwifruit]

Niche shift between polyploid and diploid plants is an important requirement for the success of polyploid. Diploid, tetraploid, and hexaploid of kiwifruit distribute in different areas. Whether there is obvious niche differentiation and the major environmental factors which could influence the ecological niche of different ploidy kiwifruits are still unknown. Based on the natural distribution information collected from literature and by field works, the maximum entropy model (MaxEnt) was used to predict the potentially suitable ranges and the major climatic factors affecting distribution of different ploidy kiwifruits. Niche divergence between different ploidy kiwifruits was quantified by niche identity test. The results showed that there were obvious differences in the potential suitable areas of different ploidy kiwifruits. Diploid occurred in lower altitude Hunan foothills. Tetraploid nearly overlapped with diploid but tended to northern Guizhou and eastern Chongqing. Hexaploid were centered in Guizhou Plateau, northwestern Hunan, southwestern Hubei and southern Shanxi. Hexaploid kiwifruits preferred higher altitudes and latitudes. In addition, the hexaploid had wider highly suitable areas. Results of niche identity test showed overlapped niches between diploid and tetraploid, and different niches between diploid/tetraploid and hexaploid kiwifruits. Minimum temperature of the coldest month (Bio6) and precipitation of the driest month (Bio14) were key environmental factors driving the niche shift of ploidy kiwifruits. Polyploid kiwifruits could maintain a higher probability of existence under lower Bio6 and Bio14, which indicated more extreme niche in cold and arid mountains for polyploids.