A biogeographic and evolutionary analysis of the flora of the North-eastern cerrado, Brazil

<b>Background</b>: The forest-savanna habitat switching is thought to have been a recurrent event in evolutionary history. Notwithstanding, the centre of the Cerrado, a large biogeographic domain, may be hypothesised to be a region with historical climatic stability and thus is predicted to contain high richness of cerrado species and the presence of few species from adjacents domains. <b>Aims</b>: We tested if today’s flora of the north-eastern cerrado (NC), a peripheral province of the domain, demonstrated an observable gradient in their distribution from centre of the Cerrado towards adjacents domains. <b>Methods</b>: We compiled vegetation survey data for 178 sites in the cerrado of north-eastern Brazil. Distribution patterns of plant taxa were assessed using multivariate techniques. <b>Results</b>: We recorded 1071 species in 390 genera and 85 families. Almost 40% were monogeneric families and ca. 50% were monospecific genera. The species composition in the NC followed a gradient related to the distance from the centre of the Cerrado towards its periphery. <b>Conclusions</b>: We show that the NC flora is unique and much richer than previously thought and that it is likely to be an outcome of evolutionary processes and of today’s intermixing of species from adjacent formations.

背景：森林-稀树草原生境转换被认为是进化历程中反复出现的事件。尽管如此，作为大型生物地理域的塞拉多（Cerrado）核心区域，可被推测为历史气候稳定的区域，因此预计其拥有丰富的塞拉多物种，且仅存在少量来自相邻生物地理域的物种。
研究目标：本研究针对作为塞拉多生物地理域外围分区的东北塞拉多（north-eastern cerrado，简称NC）的现存植物区系，检验其分布是否呈现出可观测的、从塞拉多核心区域向相邻区域渐变的格局。
研究方法：本研究整理了巴西东北部塞拉多区域内178个样地的植被调查数据，采用多变量分析技术对植物类群的分布格局进行评估。
研究结果：本研究共记录到隶属于85科、390属的1071种植物。其中近40%为单属科，约50%为单种属。东北塞拉多的植物区系组成呈现出与从塞拉多核心区域到外围的距离相关的渐变格局。
研究结论：本研究证实，东北塞拉多植物区系具有独特性，且物种丰富度远高于此前的认知，其形成可能是进化过程与当前相邻植被类型间物种混合共同作用的结果。