Instituto Tecnológico Vale, Rua Boaventura da Silva, 955, Bairro Umarizal, Belém, Brazil.
Institute of Ecology and Earth Sciences, University of Tartu, Liivi 2, Tartu 50409, Estonia.
Ann Bot. 2023 Mar 8;131(2):261-274. doi: 10.1093/aob/mcac111.
The Atlantic Forest biodiversity hotspot is a complex mosaic of habitat types. However, the diversity of the rain forest at the core of this complex has received far more attention than that of its marginal habitats, such as cloud forest, semi-deciduous forest or restinga. Here, we investigate broad-scale angiosperm tree diversity patterns along elevation gradients in the south-east Atlantic Forest and test if the diversity of marginal habitats is shaped from the neighbouring rain forest, as commonly thought.
We calculated phylogenetic indices that capture basal [mean pairwise phylogenetic distance (MPD)] and terminal [mean nearest taxon distance (MNTD)] phylogenetic variation, phylogenetic endemism (PE) and taxonomic and phylogenetic beta diversity (BD and PBD) for 2074 angiosperm tree species distributed in 108 circular sites of 10 km diameter across four habitat types i.e. rain forest, cloud forest, semi-deciduous forest and coastal vegetation known as restinga. We then related these metrics to elevation and environmental variables.
Communities in wetter and colder forests show basal phylogenetic overdispersion and short phylogenetic distances towards the tips, respectively. In contrast, communities associated with water deficit and salinity show basal phylogenetic clustering and no phylogenetic structure toward the tips. Unexpectedly, rain forest shows low PE given its species richness, whereas cloud and semi-deciduous forests show unusually high PE. The BD and PBD between most habitat types are driven by the turnover of species and lineages, except for restinga.
Our results contradict the idea that all marginal habitat types of the Atlantic Forest are sub-sets of the rain forest. We show that marginal habitat types have different evolutionary histories and may act as 'equilibrium zones for biodiversity' in the Atlantic Forest, generating new species or conserving others. Overall, our results add evolutionary insights that reinforce the urgency of encompassing all habitat types in the Atlantic Forest concept.
大西洋森林生物多样性热点是一个复杂的栖息地类型镶嵌体。然而，与核心雨林相比，这种复杂结构的边缘栖息地，如云雾林、半落叶林或休息区，受到的关注要少得多。在这里，我们沿着东南大西洋森林的海拔梯度调查了被子植物树多样性模式，并检验了边缘栖息地的多样性是否如普遍认为的那样，是由相邻的雨林塑造的。
我们计算了捕捉基础[平均成对系统发育距离（MPD）]和末端[最近分类单元距离的平均值（MNTD）]系统发育变异、系统发育特有性（PE）以及分类和系统发育β多样性（BD 和 PBD）的系统发育指数，这些指数适用于分布在四个栖息地类型（雨林、云雾林、半落叶林和沿海植被称为休息区）的 108 个 10km 直径圆形站点的 2074 种被子植物树。然后，我们将这些指标与海拔和环境变量相关联。
在更湿润和更寒冷的森林中，群落表现出基础系统发育离散度和末端短系统发育距离。相比之下，与水分不足和盐分相关的群落表现出基础系统发育聚类和末端无系统发育结构。出乎意料的是，雨林的特有物种丰富度较低，而云雾林和半落叶林的特有物种丰富度异常高。除休息区外，大多数栖息地类型之间的 BD 和 PBD 是由物种和谱系的周转率驱动的。
我们的结果与所有大西洋森林边缘栖息地类型都是雨林子集的观点相矛盾。我们表明，边缘栖息地类型具有不同的进化历史，并且可能在大西洋森林中充当生物多样性的“平衡区”，产生新的物种或保护其他物种。总的来说，我们的研究结果提供了进化方面的见解，强化了在大西洋森林概念中包含所有栖息地类型的紧迫性。
