埃塞俄比亚和厄立特里亚种子植物区系组成、多样性格局和特有性
Floristic Composition,Diversity and Endemism Patterns of Seed Plants in Ethiopia and Eritrea,in the Horn of Africa

植物区系研究的核心任务是从多种角度去阐明和理解特定地区的植物多样性模式和植物区系的组成,从而制定有效的保护方案,特别是在生物多样性相对丰富但由于气候和人为驱动的环境变化而受到高度威胁的热带地区。埃塞俄比亚和厄立特里亚位于全球生物多样性热点区域之一的非洲之角。然而,该地区的植物多样性以及植物区系组成还不清楚,而同时其生物多样性又受到非常严重的威胁。因此,通过研究该地区植物区系的组成以及植物的空间格局对于该地区的植物多样性保护有着重要意义。本研究利用埃塞俄比亚和厄立特里亚植物志以及在线数据库,重新构建了该地区的植物多样性数据信息库。利用数据库中植物信息进行多重多样性指标的空间尺度分析,从而确定该地区植物多样性空间分布格局以及划分植物区系等。我们通过0.5°× 0.5°栅格化的方式对埃塞俄比亚和厄立特里亚进行空间尺度划分,利用种子植物在属、种和特有种水平上的分类学和系统发育学的β多样性相似性进行聚类分析,并对聚类结果进行相似性(ANOSIM)检验。最终,埃塞俄比亚和厄立特里亚植物区被划分为两个植物区系亚省、五个植物区系区和十三个植物区系亚区。其中西南植物区系亚省主要位于高海拔区域,西北植物亚省主要位于低海拔区域。5个植物区系区主要与区内植物组成、地理差异等有关系。通过物种周转率的研究发现,高山区域物种多样性高,但存在较高的物种周转率。同时,由于高山对物种信息交流的阻碍作用,位于该区域高山东西两侧的植物区系区之间的物种周转率很低。埃塞俄比亚和厄立特里亚特有植物分布热点地区主要位于该地区高山区域,通过加权特有性的分析,确定出三个特有植物分布中心,分别是北部的西蒙山特有植物中心,位于中部的舍瓦高地特有植物中心,位于南部的巴里山特有植物中心。三个特有植物分布中心中西蒙山和巴里山中心特有程度最高,而舍瓦高地特有植物中心是首次被提出。综上所述,通过我们对埃塞俄比亚和厄立特里亚的植物区系的划分以及特有植物的空间格局的分析,为进一步研究该地区植物区系间的起源与进化关系的研究提供了基础理论依据,也为该地区的生物多样性保护和保护区的规划建设等提供了科学依据。

The central task in floristic study is to elucidate and understand the Patterns of plant diversity and the assemblages of floristic systems in particular regions from different perspectives so as to develop and prioritize effective conservation plans especially in tropics where biodiversity is relatively rich but,highly threatened due to climatic change and other anthropogenic driven environmental changes.Ethiopia and Eritrea are among the tropical countries located in the horn of Africa and known for their rich biodiversity resources.However the floristic compositions of their flora had not been clearly known based on the characteristics of its biota.The diversity and endemism patterns of its plant communities also had not been clearly described while at the same time the flora is the most threatened one implying that the study of floristic compositions and the understanding of the spatial patterns of plant diversity are paramount in this region to address such gaps and protect the biodiversity of the region.So in this study we classified the flora of the areas into meaningful floristic units and assessed and mapped the diversity and endemism patterns of plant communities across the region.In order to carry out these,we quantified different diversity measuring metrics and analyzed their patterns at a uniform spatial scale of 0.5°×0.5°grid cells.The flora of the area was quantitatively classified into meaningful floristic units based on the similarity patterns of these 0.5°×0.5°grad cells in terms of their native seed plants taxonomic and phylogenetic β diversity at the genus,total and endemic species levels.Hierarchical cluster analysis was performed to divide this flora according to the described parameters and ANOSIM(analysis of similarities)was used to evaluate the significance differences between the derived cluster results.The results of the analysis revealed that based on its plant characteristics the flora of Ethiopia and Eritrea can be divided in to two floristic sub-provinces(the south west and the north east),five flora districts and thirteen floristic sub-districts.While the two floristic sub-provinces were found to be more related to the elevation gradients of the region in which the southwest sub-province was almost found to be belonged to the highland parts of the region and the north east sub-province was found to be located in the lowland and warmer parts of the areas,the five floristic districts were found to be more attributed to the variation in plant species compositions and geographical locations among different sites.Our result also showed very variable spatial plant diversity patterns across the region and found that the montane parts of the region are generally the areas of high plant species diversity in the region.Owned to the barriers from the Rift Valley in the region,the species turnover rate between the western and the eastern highlands was found to be very low.Using species weighted endemism index three plant species endemism centres were detected in the flora of Ethiopia and Eritrea including the Simien mountain centres,the east upland show a centre and the Bale mountain centre.The Simien and Bale mountains endemic plant species centres were found to have the highest degree of plant species endemism while the East upland showa centre was the first time to be detected.These centres of unique(endemic)plant species were also found concentrated to the highland parts of the region in the northern,central and south eastern parts Ethiopia.Overall our study has provided a basic scientific frameworks and additional insights to the flora of the region from different perspectives.The obtained results will have a great significance in different aspects.The derived floristic systems provide spatially explicit framework units that help in many broad scale evolutionary and ecological studies as well as in large scale conservation analyses.The mapped diversity patterns and the detected endemism centres help in guiding and planning effective biodiversity conservation programs in the region by specifying potential areas and species of focus for conservation.

非洲之角; 植物区系; 系统发育多样性; 物种周转率; 特有植物分布中心;

Horn of Africa; floristic divisions; phylogenetic diversity; species turnover; endemism centers;

The funding project of Sino-Africa Joint Research Center,CAS,China(Y323771W07 and SAJC201322); National Natural Science Foundation of China(31800176);

辛海平;

Q948.5

24704443K