Drivers of cryptic species coexistence in stream ecosystems – a case study using gammarid amphipods from Sicily

溪流生态系统中神秘物种共存的驱动因素——使用西西里岛伽马科片足类动物的案例研究

• 批准号: 418153139
• 负责人: Professor Dr. Florian Leese
• 金额: --
• 依托单位: Abteilung Aquatische Ökologie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/418153139?language=en
• 关键词: Drivers; cryptic; species; coexistence; stream

Over the past decades, DNA-based bioassessments have uncovered that species diversity has been greatly underestimated due to the presence of cryptic species. Because cryptic species are morphologically undistinguishable, the true number of cryptic species as well as their distribution and ecological characteristics remain largely unknown. Present evidence supports that cryptic species typically do not co-occur but rather live in different regions or if co-occurring in a region, they are rarely found in syntopy. This finding is expected given that coexistence is typically enabled by niche differences between different species. As cryptic species are phylogenetically very similar, it is often assumed that they resemble 'ecological clones' and thus may not coexist in view of competition exclusion theory. Interestingly, few studies have reported coexisting cryptic species. One prominent example is the occurrence of six cryptic species of a gammaridean amphipod taxon (Echinogammarus sicilianus) in a river basin in Sicily. This finding is unexpected and raises the question whether co-existence is stable or unstable, and how it is maintained. Different mechanisms have been proposed by community ecological theory which allow stable coexistence of species: i) resource partitioning, ii) spatial or temporal avoidance strategies, and iii) density-dependent biotic mechanisms such as apostatic selection that balance communities. In our project, we will use the exceptional case of cryptic species co-occurrence in Sicily as an example to study how different cryptic species are partitioned at the local scale and over time. To answer this question, we will sample the available stream microhabitats in the river network over the course of one year. We will use DNA-based species assignment methods to identify all specimens. Subsequently, we will study the gut contents and microbiome of the different species per site and microhabitat using DNA metabarcoding to analyse whether there is a dietary specialisation among the cryptic species. With isotopic analyses we will back up the data on trophic specialisation. In a last step we will study the prevalence and diversity of microsporidian and acanthocephalan parasites in the individual cryptic species. We will test whether prevalence and host specificity changes over time in order to test the density-dependent control of cryptic species through parasites. Finally, all data will be used together with land-use data to test competing hypotheses on the impact of abiotic and biotic factors on species presence and coexistence. From this we will derive whether coexistence of cryptic species is stable or unstable. While only a single such case of cryptic species co-occurring has been reported so far, the results from this project will provide a blueprint on how to combine different methodological and conceptual approaches in ecology to analyse and understand drivers of cryptic species coexistence in freshwater habitats.

在过去的几十年里，基于DNA的生物评估发现，由于神秘物种的存在，物种多样性被大大低估。由于隐种在形态上难以区分，隐种的真实数量以及它们的分布和生态特征在很大程度上仍然未知。目前的证据支持，神秘的物种通常不共现，而是生活在不同的地区，或者如果共现在一个地区，他们很少被发现的同生。这一发现是预期的，因为共存通常是由不同物种之间的生态位差异实现的。由于隐种在遗传学上非常相似，人们通常认为它们类似于“生态克隆”，因此根据竞争排斥理论，它们可能不会共存。有趣的是，很少有研究报道共存的神秘物种。一个突出的例子是在西西里的一个流域发现了6个隐种的伽马阶片足类（Echinogammarus sicilianus）。这一发现是出乎意料的，并提出了一个问题，即共存是稳定的还是不稳定的，以及它是如何维持的。群落生态学理论提出了不同的机制，允许物种稳定共存：i）资源分配，ii）空间或时间的回避策略，iii）密度依赖的生物机制，如平衡群落的离位选择。在我们的项目中，我们将使用特殊的情况下，在西西里作为一个例子，研究如何在当地规模和随着时间的推移，不同的隐藏物种的共存。为了回答这个问题，我们将在一年的时间里对河网中可用的溪流微生境进行采样。我们将使用基于DNA的物种分配方法来识别所有标本。随后，我们将研究每个站点和微生境的不同物种的肠道内容物和微生物组，使用DNA元条形码分析隐藏物种之间是否存在饮食专业化。通过同位素分析，我们将支持营养专门化的数据。在最后一步中，我们将研究微孢子虫和棘头虫寄生虫在个体隐种中的流行率和多样性。我们将测试流行率和宿主特异性是否随着时间的推移而变化，以测试通过寄生虫对隐藏物种的密度依赖性控制。最后，所有数据将与土地使用数据一起用于检验关于非生物和生物因素对物种存在和共存的影响的相互竞争的假设。由此我们将得出隐种共存是稳定的还是不稳定的。虽然到目前为止只报告了一个神秘物种共存的案例，但该项目的结果将提供一个蓝图，说明如何将生态学中不同的方法和概念方法联合收割机结合起来，以分析和理解淡水栖息地中神秘物种共存的驱动因素。