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演化历史中反复出现的事件。尽管如此，塞拉多（Cerrado）作为大型生物地理域，其核心区域被推测为具有历史气候稳定性的区域，因此预计该区域拥有丰富的塞拉多物种，且仅存在少量来自邻近生物域的物种。
**研究目的**：我们旨在验证，作为该生物地理域边缘生物省的巴西东北部塞拉多（NC）的现存植物区系，是否呈现出从塞拉多核心区域向邻近生物域的可观测分布梯度。
**研究方法**：我们汇编了巴西东北部塞拉多地区178个样地的植被调查数据，并采用多元分析技术对植物类群的分布模式进行评估。
**研究结果**：本次研究共记录到85科、390属、1071种植物，其中近40%为单属科，约50%为单种属。东北部塞拉多的物种组成呈现出随与塞拉多核心区域距离增加而向边缘过渡的梯度特征。
**研究结论**：本研究表明，东北部塞拉多的植物区系具有独特性，且物种丰富度远高于此前预期；其形成可能是演化过程与当前邻近植被型间物种混合共同作用的结果。