Geographical Pattern Of Orchid Diversity In China And Its Environmental Correlation

Biodiversity serves as the foundation for human survival and development.However,with the declining trend of biodiversity caused by climate change and human interference,the conservation of biodiversity has become a global concern.In the past,studies using taxonomic diversity alone were unable to provide comprehensive information on the formation and evolution of biodiversity.In recent years,by constructing regional species trees of life and functional trait trees,and by combining geographic distribution data of species,a more comprehensive evaluation of biodiversity at the phylogenetic and functional levels can be achieved.Orchidaceae is not only one of the most species-rich and widely distributed families of angiosperms,but it is also a critical taxon for biological conservation.In this study,the diversity and protection of orchids in China were explored by investigating 1,556 orchid species of181 genera.Geographic distribution data,phylogenetic and functional trait clustering trees,and four types of environmental data were used in the analysis.Taxonomic,phylogenetic and functional diversity indices were calculated.Correlation analysis was performed using the Pearson analysis.RDA analysis and hierarchical partitioning analysis were used to obtain the relationship between environmental factors and all types of diversity indices.The objective of this study was to explore the geographical distribution patterns of taxonomic,phylogenetic and functional diversity of orchids in China and their environmental influences,and also explore the reasons for the formation of diversity of orchids,as well as analyze the priority conservation areas of orchids by combining three types of diversity indices and provide insights for the conservation of orchid diversity.The main results are as follows:1.Orchids in China are more intensively distributed in southeastern Tibet,southwestern mountain regions,Hainan Island and Taiwan Island.Epiphytic orchids have a narrow geographical distribution,while terrestrial ones have a broader distribution.The taxonomic diversity of orchids is primarily influenced by the minimum temperature in the coldest month(MTCM),the coefficient of seasonal variation of temperature(TS),and the annual precipitation(AP).2.The geographical distribution patterns of diversity(SR,PD,FD)and endemism(WE,PE,FE)at three levels(taxonomy,phylogeny and function)are roughly the same.The highest values are in the southwestern mountain regions and Taiwan Island.PD and FD are mainly influenced by climatic factors(MTCM、AP).Environmental factors may not fully explain the patterns of endemism(WE,PE,FE),as other factors,such as mountains that served as refuges for some endemic species during the ice age,could dominate.3.The distribution patterns of standardized phylogenetic diversity(PDses)and standardized functional diversity(FDses)of epiphytic orchids were mainly dominated by climatic factors(MTCM,TS,AP),resulting in the lowest diversity in the warm and humid southwest.Habitat heterogeneity led to the lowest PDses in the Hengduan Mountains,while FDses exhibited the lowest values in the Hengduan Mountains and northern extreme environments,likely due to the evolution of functional convergence.4.The phylogenetic structure of epiphytic orchids diverged in the southeast and clustered in the northwest,which is consistent with the tropical niche conservation hypothesis(TNC).Conversely,the phylogenetic structure of epiphytic orchids clustered in the southeast and became more random in the colder northwest,which is consistent with the Out of the Tropics hypothesis(OTT).This contrast may be due to the fact that epiphytic orchids have a higher diversification rate than terrestrial orchids,which promotes the occurrence of OTT.5.Both epiphytic and terrestrial orchids exhibited functional structures that clustered in the southeast and showed a random pattern in the northwest,which was significantly impacted by climate,particularly the minimum temperature in the coldest month(MTCM),the coefficient of seasonal variation of temperature(TS),and the annual precipitation(AP).6.The distribution pattern of phylogeny and functional structure of epiphytic orchids exhibited a generally consistent pattern,whereas the distribution pattern of phylogeny and functional structure of terrestrial orchids varied.The inconsistency between phylogeny and functional structure may be attributed to multiple ecological factors.7.According to the research findings,the priority areas for orchid conservation in China should be located in southeastern Tibet,the southern and eastern edges of the Hengduan Mountains,the southwestern mountains,western Guangxi,southern Guangdong,Taiwan Island,and Hainan Island.Many of these regions do not have adequate protection through existing protected areas,and significant conservation gaps exist.Therefore,it is recommended that new protected areas be established in these regions to ensure the conservation of orchids and their associated biodiversity.In conclusion,the distribution pattern of orchid diversity in China is primarily influenced by climate,with epiphytic orchids being more susceptible to climatic factors than terrestrial orchids.The tropical niche conservation hypothesis(TNC)and the out of the tropics hypothesis(OTT)could explain the patterns of phylogenetic structure of terrestrial and epiphytic orchids,respectively.The functional structures of both terrestrial and epiphytic orchids are largely determined by climate.Furthermore,consistent patterns of phylogenetic and functional diversity and structure distribution were observed among epiphytic orchids,whereas terrestrial orchids exhibited inconsistencies in their patterns of diversity and functional diversity and structure distribution.