Plant Diversity And Floristic Research In Tropical East Africa

Tropical East Africa is one of the most important biodiversity hotspots in the world.However,it is not clear about the species list,distribution pattern,floristic composition and conservation of plant diversity in the region.In this study,the plant diversity database of Tropical East Africa was constructed through the Flora of Tropical East Africa,specimen digitization and online databases.The database contains the species list and it's distribution information of Tropical East Africa.Based on this database,the spatial pattern,specimen collection strategy,floristic construction and conservation of plant diversity in Tropical East Africa were studied.The main results are as follows:(1)The spatial pattern of plant diversity in tropical East Africa.According to the plant diversity database of Tropical East Africa,16142 species of plants belonging to 248 families and 2305 genera were were sorted out.Among them,there are 15550 angiosperms,23 gymnosperms,579 ferns and lycopodites.The spatial distribution of plant diversity in tropical East Africa is uneven,with plant diversity hotspots mainly in central and southwestern Kenya,southwest and northeast Tanzania,western Rwanda and Burundi,and the coastal zone of tropical East Africa.Through the analysis of spatial distribution pattern of different types of plants by species richness-environment model,it is found that energy factors and environmental heterogeneity are the best explanation for the spatial distribution pattern of gymnosperms,pteridophyte,and energy and water factors are the best explanation for the spatial distribution pattern of angiosperms.(2)Inventory incompleteness and collection priority on the plant diversity in tropical East Africa.Based on the 0.25 ° rasterization of the region,the species distribution data in the database was compared with the predicted species richness.It is found that the spatial pattern of plant specimen collection in tropical East Africa is very uneven,in which 16% of the regions have no collection and more than 50% of the regions have incomplete collection.The inventory incompleteness is mainly affected by species richness,road density,national boundaries,regional security and other factors.Based on the spatial analysis of the weighted species richness and inventory incompleteness,the priority collection areas were determined,including thewestern Kenya,southern Tanzania and the border between countries.(3)The floristic composition and endemism center of Tropical East Africa.Based on the analysis of taxonomic ?-diversity and phylogenetic ?-diversity of genera,total species and endemic species,tropical East Africa was divided into 4 floristic districts and 9 floristic sub-districts.Among them,the East Africa Coastal Zone and the Southern Tanzania Flora District have the highest plant diversity,and the Northeast Kenya Flora District have the lowest species and endemic species turnover rate.The highest turnover rate is the Mt.Kenya to Lake Rukwa Floristic District.According to the endemic species richness,weighted endemism and phylogenetic endemism,nine endesim centers in tropical East Africa are determined,which are located in the main mountains and surrounding areas of East Africa.(4)The conservation research of endangered plants in tropical East Africa.1821 endangered plants in tropical East Africa were selected from International Union for Conservation of Nature(IUCN).A study of the changes in its potential distribution area under climate change found that in the next 30-50 years,about 100 species of plants in the region will become extinct,and more than half of the plant 's habitat will be reduced.The IUCN categories will also change greatly,many species from "Least Concern" to "Vulnerable","Critically Endangered" or even "Extinct".However,there are some species whose endangered categories have declined.By analyzing the Red List Index and species richness,and combining the spatial distribution patterns of different IUCN endangered species,the East Africa coast,southwestern Tanzania and high mountain areas were identified as priority hotspot areas for protection.Based on the above research results,tropical East Africa is an important plant diversity distribution area with high plant richness and endemism.We suggest to strengthen the plant diversity survey in the area to quickly supplement regional plant diversity data;strengthen the research on the geographical pattern,origin and evolution of the alpine plant diversity in East Africa;deeply assess the IUCN categories of endangered species in this area,and carry out the research on Conservation strategies.This study is of great significance to the formation mechanism and conservation of plant diversity in tropical East Africa.