Study On Taxonomic Status And Habitat Suitability Distribution Of Three PSESP Acer Species In Sichuan Province

China is the modern diversity distribution center of the Acer,which is rich in species,but some species also have problems such as disputed taxonomic status or unclear genetic relationship.Acer catalpifolium,A.guanense and A.leipoense are mainly distributed in Sichuan Province.They are extremely small populations of wild plants in southwest China,but so far,there have been few studies on these three species.Among them,the taxonomic status of A.catalpifolium and A.guanense is controversial.The systematic relationship of A.leipoense is not clear.In addition,relevant studies have not been carried out on their habitat suitability distribution.All these directly affect the effective protection and utilization of these species.Based on field surveys,trait measurement statistics and micro-morphological characteristics,this study uses correlation analysis,principal component analysis(PCA)and other methods,combined with chloroplast complete gene and nuclear gene ITS phylogeny analysis,to explore the taxonomic status of A.catalpifolium and A.guanense.The phylogenetic relationship between these three species and their relatives was described.At the same time,based on the existing distribution data,using the maximum entropy model(Max Ent)to analyze,predict the potential suitable distribution areas of A.catalpifolium and A.leipoense,determine the main environmental variable factors,and discuss the potential suitable distribution areas of climate change.The main results are as follows:(1)A.catalpifolium,A.amplum,A.amplum subsp.jianshuiense,A.amplum subsp.tientaiense,A.nayongense,A.nayongense var.hunanense,Acer cappadocicum,and Acer longipes show significant differences in leaf morphology.The main traits are discontinuous.On the molecular system tree,A.catalpifolium,A.amplum,Acer cappadocicum,and Acer longipes are also in different positions.Therefore,A.catalpifolium should not be used as a subspecies of other species,and should be retaining the taxonomic status of the original independent species.(2)There are obvious differences between A.guanense and A.oblongum,A.oblongum var.omeiense,A.oblongum var.pachyphyllum,A.oblongum var.latialatum,and A.oblongum var.concolor in petiole length and leaf veins,although molecular evidence shows A.guanense is closely related to A.oblongum,but it is not recommended to treat it as a synonym for A.oblongum.(3)Both A.leipoense and A.yangbiense have been proved to be closely relationship in morphological characters and molecular level.(4)The most suitable distribution area of A.catalpifolium is the low altitude(<1,000m)area with the driest season precipitation of 31.2~65.2mm in central Sichuan and the coldest month temperature in winter between-4.2~3?,with an area of about2.23 ×104km2,the long-term climate warming trend may have a negative impact on the distribution of A.catalpifolium;the most suitable distribution area of A.leipoense is the dry and wet seasons with monthly temperature change of less than 10°C in central Sichuan and winter precipitation of less than43 mm,with an area of about 2.23 ×104km2.Finally,the morphological characters of the three Acer are described and supplemented,and the key to the related species are provided.