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Coexistence and bush encroachment in African savannas: The role of the regeneration niche
Functional Ecology ( IF 4.6 ) Pub Date : 2021-01-18 , DOI: 10.1111/1365-2435.13759 J.R. Lewis 1 , G.A. Verboom 1 , E.C. February 1
中文翻译：
非洲稀树草原的共存和灌木丛侵占：再生生态位的作用
更新日期：2021-03-08
Functional Ecology ( IF 4.6 ) Pub Date : 2021-01-18 , DOI: 10.1111/1365-2435.13759 J.R. Lewis 1 , G.A. Verboom 1 , E.C. February 1
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- Globally there is increasing concern over the biodiversity and economic losses associated with bush encroachment. The dominant species responsible for bush encroachment in Africa belong to the mimosoid genera Senegalia and Vachellia, with previous research identifying Vachellia as the more aggressive invader. We asked whether these genera have evolved different traits to enable germination and establishment among competitively superior grasses. We hypothesised that these traits enable coexistence at local scales and underpin differences in invasiveness.
- We conducted a large greenhouse pot experiment to quantify functional trait differences between the two genera during seedling establishment both in the presence and absence of grasses. We also examined differences in seed morphology and tested whether co‐occurrence of the two genera at the plot scale is greater than expected by chance.
- Our results showed that Vachellia grew faster and taller than Senegalia in the absence of competition from grasses. In the presence of grasses, however, Senegalia increased root tissue density while Vachellia did not. The seed coats of Vachellia species were thicker than those of Senegalia, and their seeds were spherical while those of Senegalia were discoid. The two genera coexist at a local (plot) scale.
- We speculated that the thicker seed coat and spherical seed shape of Vachellia reflect its primarily endozoochorous dispersal mode, while the thinner seed coat and more discoid seeds of Senegalia reflect its use of wind dispersal. Since animal dispersal is directed, promoting the movement of seed into sites frequented by animals, and in which competition from grasses and fire has been removed, animal dispersal may contribute to the greater invasiveness of Vachellia. Once established in such sites, coexistence at the local scale is facilitated by differences in root tissue density with low‐density root tissue allowing for rapid resource acquisition and growth in Vachellia, and high‐density root tissue enabling slower but more persistent growth in Senegalia.
- Where previous research has focussed on environmental filtering, competition, predation or facilitation as explanations of plot‐scale phylogenetic overdispersion, our work suggests a potential role for regeneration niche in structuring local co‐occurrence.
中文翻译：
非洲稀树草原的共存和灌木丛侵占：再生生态位的作用
- 在全球范围内，人们越来越关注与灌木丛入侵相关的生物多样性和经济损失。属于mimosoid属负责非洲灌木侵占的优势种Senegalia和Vachellia，与先前的研究确定Vachellia为更积极的入侵者。我们询问这些属是否已进化出不同的性状，以使其能够在竞争优势的草丛中发芽和定植。我们假设这些特征使地方尺度上能够共存，并支持入侵性的差异。
- 我们进行了一个大型温室盆栽实验，以定量在有无草存在的幼苗建立过程中两个属之间的功能性状差异。我们还检查了种子形态的差异，并测试了两个属在地块比例上是否同时存在是否大于预期。
- 我们的研究结果表明，Vachellia长得更快，长得比Senegalia在没有从草的竞争。在草的存在，然而，Senegalia增加的根组织密度而Vachellia没有。的种皮Vachellia物种较厚Senegalia，及其种子为球状，而那些的Senegalia是盘状。这两个属以局部（图）比例共存。
- 我们推测的较厚种皮和球形种形状Vachellia反映其主要endozoochorous扩散模式，而较薄的种皮和的更盘状种子Senegalia反映其使用风扩散的。由于直接进行动物传播，促进了种子移动到动物经常光顾的地方，并且已经消除了草和火的竞争，因此动物传播可能会促进Vachellia的入侵。一旦在这样的地点建立，根组织密度与低密度根组织的差异将促进局部规模的共存，从而使Vachellia迅速获得资源并生长以及高密度的根组织使塞内利亚（Senegalia）的生长缓慢而持久。
- 以前的研究集中在环境过滤，竞争，掠夺或便利化上，作为对样地规模的系统发育过度分散的解释，我们的工作表明，再生生态位在构建局部共现中可能发挥作用。
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