Constant diversification rates of endemic gastropods in ancient Lake Ohrid: ecosystem resilience likely buffers environmental fluctuations
Constant diversification rates of endemic gastropods in ancient Lake Ohrid: ecosystem resilience likely buffers environmental fluctuations
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DOI：
10.5194/bg-12-7209-2015
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发表时间：
2015-01-01
期刊：
影响因子：
4.9
通讯作者：
Wilke, T.
中科院分区：
文献类型：
--
作者：
Foeller, K.;Stelbrink, B.;Wilke, T.
古代湖泊是特有淡水物种的关键生态系统。这种高度的地方性生物多样性已被证明主要是湖内多样化的结果。虽然这种多样化模式的主要作用得到了普遍承认，但古代湖泊的实际多样化速度仍然鲜为人知。至少有四种类型可以想象。多样化比率可能会随着时间的推移保持不变，可能会波动，多样化初期的比率可能会更高，或者在殖民和随后的多样化之间可能会有一个明显的滞后阶段。由于了解古代湖泊环境中物种多样化的节奏可能有助于揭示导致物种形成和灭绝的潜在过程，我们在这里以巴尔干湖奥赫里德为模式系统，以该湖中最大的物种--非金龟科水生动物为模式分类群，研究多样性比率随时间的变化以及各自的驱动因素。基于系统发育、分子时钟、通过时间的谱系图和多样化比率分析，我们发现这个潜在的单系类群相对较老，很可能是以恒定的多样化速度进化的。SCOPSCO(关于过去奥赫里德湖物种形成条件的科学合作)深层钻探计划的初步数据确实表明奥赫里德湖存在严重的环境/气候扰动迹象。然而，到目前为止，没有证据表明发生了灾难性的环境事件。因此，我们认为，在地方性腹足动物中观察到的持续多样化是由两个因素造成的：(I)奥赫里德湖可能缺乏灾难性的环境事件和/或(Ii)可能具有较高的生态系统弹性，缓冲了环境变化。奥赫里德湖独特的水深测量、持续的构造活动和岩溶水文作用可能是该湖高生态系统韧性的潜在因素。目前的研究不仅有助于实现SCOPSCO深部钻探计划的总体目标之一--推断奥赫里德湖生物进化的驱动力。它还可能加强我们对生态系统弹性一般如何在孤立的生态系统中促进相对恒定的多样化比率的理解。然而，我们鼓励未来的研究，以检验关于奥赫里德湖没有灾难性事件的假设。这些研究应该以整个湖泊地质历史的高分辨率数据为基础，它们可能会涉及沉积物化石记录中的信息，不仅是腹足类，而且还有其他特有类群的信息。
Ancient lakes represent key ecosystems for endemic freshwater species. This high endemic biodiversity has been shown to be mainly the result of intra-lacustrine diversification. Whereas the principle role of this mode of diversification is generally acknowledged, actual diversification rates in ancient lakes remain little understood. At least four types are conceivable. Diversification rates may be constant over time, they may fluctuate, rates may be higher in the initial phase of diversification, or there may be a pronounced lag phase between colonization and subsequent diversification. As understanding the tempo of diversification in ancient lake environments may help reveal the underlying processes that drive speciation and extinction, we here use the Balkan Lake Ohrid as a model system and the largest species flock in the lake, the non-pyrgulinid Hydrobiidae, as a model taxon to study changes in diversification rates over time together with the respective drivers.Based on phylogenetic, molecular-clock, lineage-through-time plot, and diversification-rate analyses we found that this potentially monophyletic group is comparatively old and that it most likely evolved with a constant diversification rate. Preliminary data of the SCOPSCO (Scientific Collaboration On Past Speciation Conditions in Lake Ohrid) deep-drilling program do indicate signatures of severe environmental/climatic perturbations in Lake Ohrid. However, so far there is no evidence for the occurrence of catastrophic environmental events. We therefore propose that the constant diversification rate observed in endemic gastropods has been caused by two factors: (i) a potential lack of catastrophic environmental events in Lake Ohrid and/or (ii) a probably high ecosystem resilience, buffering environmental changes. Parameters potentially contributing to the lake's high ecosystem resilience are its distinct bathymetry, ongoing tectonic activities, and karst hydrology.The current study not only contributes to one of the overall goals of the SCOPSCO deep-drilling program - inferring the driving forces for biotic evolution in Lake Ohrid. It might also enhance our understanding of how ecosystem resilience, in general, may promote relatively constant diversification rates in isolated ecosystems. However, we encourage future studies testing hypotheses about the lack of catastrophic events in Lake Ohrid. These studies should be based on high-resolution data for the entire geological history of the lake, and they should potentially involve information from the sediment fossil record, not only for gastropods but also for other groups with a high share of endemic taxa.