Grabowski Michał, Mamos Tomasz, Bącela-Spychalska Karolina, Rewicz Tomasz, Wattier Remi A
Department of Invertebrate Zoology and Hydrobiology, University of Lodz , Łódź , Poland.
Laboratory of Microscopic Imaging and Specialized Biological Techniques, University of Lodz , Łódź , Poland.
PeerJ. 2017 Feb 28;5:e3016. doi: 10.7717/peerj.3016. eCollection 2017.
The Balkans are a major worldwide biodiversity and endemism hotspot. Among the freshwater biota, amphipods are known for their high cryptic diversity. However, little is known about the temporal and paleogeographic aspects of their evolutionary history. We used paleogeography as a framework for understanding the onset of diversification in : (1) we hypothesised that, given the high number of isolated waterbodies in the Balkans, the species is characterised by high level of cryptic diversity, even on a local scale; (2) the long geological history of the region might promote pre-Pleistocene divergence between lineages; (3) given that thrives both in lakes and rivers, its evolutionary history could be linked to the Balkan Neogene paleolake system; (4) we inspected whether the Pleistocene decline of hydrological networks could have any impact on the diversification of .
DNA was extracted from 177 individuals collected from 26 sites all over Balkans. All individuals were amplified for ca. 650 bp long fragment of the mtDNA cytochrome oxidase subunit I (COI). After defining molecular operational taxonomic units (MOTU) based on COI, 50 individuals were amplified for ca. 900 bp long fragment of the nuclear 28S rDNA. Molecular diversity, divergence, differentiation and historical demography based on COI sequences were estimated for each MOTU. The relative frequency, geographic distribution and molecular divergence between COI haplotypes were presented as a median-joining network. COI was used also to reconstruct time-calibrated phylogeny with Bayesian inference. Probabilities of ancestors' occurrence in riverine or lacustrine habitats, as well their possible geographic locations, were estimated with the Bayesian method. A Neighbour Joining tree was constructed to illustrate the phylogenetic relationships between 28S rDNA haplotypes.
We revealed that includes at least 13 cryptic species or molecular operational taxonomic units (MOTUs), mostly of Miocene origin. A substantial Pleistocene diversification within-MOTUs was observed in several cases. We evidenced secondary contacts between very divergent MOTUs and introgression of nDNA. The Miocene ancestors could live in either lacustrine or riverine habitats yet their presumed geographic localisations overlapped with those of the Neogene lakes. Several extant riverine populations had Pleistocene lacustrine ancestors.
Neogene divergence of lineages resulting in substantial cryptic diversity may be a common phenomenon in extant freshwater benthic crustaceans occupying areas that were not glaciated during the Pleistocene. Evolution of could be associated with gradual deterioration of the paleolakes. The within-MOTU diversification might be driven by fragmentation of river systems during the Pleistocene. Extant ancient lakes could serve as local microrefugia during that time.
巴尔干地区是全球主要的生物多样性和特有性热点地区。在淡水生物群中，双足虾类以其高度的隐性多样性而闻名。然而，关于它们进化历史的时间和古地理方面却知之甚少。我们将古地理学作为理解以下方面多样化起始的框架：（1）我们假设，鉴于巴尔干地区孤立水体数量众多，即使在局部尺度上，该物种也具有高度的隐性多样性；（2）该地区漫长的地质历史可能促进谱系间更新世前的分化；（3）鉴于[物种名称]在湖泊和河流中都能繁盛，其进化历史可能与巴尔干新近纪古湖系统有关；（4）我们研究了更新世水文网络的衰退是否会对[物种名称]的多样化产生任何影响。
从巴尔干地区各地26个地点采集的177个个体中提取DNA。所有个体都扩增了线粒体DNA细胞色素氧化酶亚基I（COI）约650 bp长的片段。在基于COI定义分子操作分类单元（MOTU）后，对50个个体扩增了核28S rDNA约900 bp长的片段。针对每个MOTU，基于COI序列估计分子多样性、分歧、分化和历史种群统计学。COI单倍型之间的相对频率、地理分布和分子分歧以中位数连接网络呈现。COI也用于通过贝叶斯推断重建时间校准的系统发育。用贝叶斯方法估计祖先出现在河流或湖泊栖息地的概率以及它们可能的地理位置。构建了邻接树以说明28S rDNA单倍型之间的系统发育关系。
我们发现[物种名称]至少包括13个隐性物种或分子操作分类单元（MOTU），大多起源于中新世。在几个案例中观察到了MOTU内显著的更新世多样化。我们证明了非常不同的MOTU之间的二次接触以及核DNA的渗入。中新世祖先可能生活在湖泊或河流栖息地，但其假定的地理定位与新近纪湖泊的定位重叠。几个现存的河流种群有更新世湖泊祖先。
谱系的新近纪分化导致大量隐性多样性可能是现存淡水底栖甲壳类动物中常见的现象，这些动物占据了更新世期间未被冰川覆盖的地区。[物种名称]的进化可能与古湖的逐渐退化有关。MOTU内的多样化可能是由更新世期间河流系统的破碎化驱动的。现存的古代湖泊在那个时期可能充当了局部微避难所。
