Gauffre-Autelin Pauline, von Rintelen Thomas, Stelbrink Björn, Albrecht Christian
Department of Animal Ecology and Systematics, Justus Liebig University, Giessen, Germany.
Museum für Naturkunde, Leibniz Institute for Evolution and Biodiversity Science, Berlin, Germany.
Parasit Vectors. 2017 Mar 6;10(1):126. doi: 10.1186/s13071-017-2043-6.
The planorbid snail Indoplanorbis exustus is the sole intermediate host for the Schistosoma indicum species group, trematode parasites responsible for cattle schistosomiasis and human cercarial dermatitis. This freshwater snail is widely distributed in Southern Asia, ranging from Iran to China eastwards including India and from the southeastern Himalayas to Southeast Asia southwards. The veterinary and medical importance of this snail explains the interest in understanding its geographical distribution patterns and evolutionary history. In this study, we used a large and comprehensive sampling throughout Indo-Malaya, including specimens from South India and Indonesia, areas that have been formerly less studied.
The phylogenetic inference revealed five highly divergent clades (genetic distances among clades: 4.4-13.9%) that are morphologically indistinguishable, supporting the assumption that this presumed nominal species may represent a cryptic species complex. The species group may have originated in the humid subtropical plains of Nepal or in southern adjacent regions in the Early Miocene. The major cladogenetic events leading to the fives clades occurred successively from the Early Miocene to the Early Pleistocene, coinciding with major periods of monsoonal intensification associated with major regional paleogeographic events in the Miocene and repeated climate changes due to the Plio-Pleistocene climatic oscillations. Our coverage of the Indo-Australian Archipelago (IAA) highlights the presence of a single clade there. Contrary to expectations, an AMOVA did not reveal any population genetic structure among islands or along a widely recognised zoogeographical regional barrier, suggesting a recent colonisation independent of natural biogeographical constraints. Neutrality tests and mismatch distributions suggested a sudden demographic and spatial population expansion that could have occurred naturally in the Pleistocene or may possibly result of a modern colonisation triggered by anthropogenic activities.
Even though Indoplanorbis is the main focus of this study, our findings may also have important implications for fully understanding its role in hosting digenetic trematodes. The existence of a cryptic species complex, the historical phylogeographical patterns and the recent range expansion in the IAA provide meaningful insights to the understanding and monitoring of the parasites potential spread. It brings a substantial contribution to veterinary and public health issues.
扁卷螺属的印度扁卷螺是印度血吸虫物种组的唯一中间宿主，该吸虫寄生虫可导致牛血吸虫病和人类尾蚴性皮炎。这种淡水螺广泛分布于南亚，从伊朗向东至中国，包括印度，以及从喜马拉雅山脉东南部向南至东南亚。这种螺在兽医和医学方面的重要性解释了人们对了解其地理分布模式和进化历史的兴趣。在本研究中，我们在整个印度 - 马来亚地区进行了大规模且全面的采样，包括来自印度南部和印度尼西亚的标本，这些地区以前研究较少。
系统发育推断揭示了五个高度分化的分支（分支间的遗传距离为4.4 - 13.9%），它们在形态上无法区分，这支持了这样一种假设，即这个假定的指名物种可能代表一个隐存物种复合体。该物种组可能起源于中新世早期尼泊尔的湿润亚热带平原或相邻的南部地区。导致这五个分支的主要分支形成事件从中新世早期到更新世早期相继发生，与中新世主要区域古地理事件相关的季风增强的主要时期以及上新世 - 更新世气候振荡导致的反复气候变化相吻合。我们对印度 - 澳大利亚群岛（IAA）的覆盖突出了那里存在一个单一分支。与预期相反，一项分子方差分析（AMOVA）未揭示岛屿之间或沿着一个广泛认可的动物地理区域屏障存在任何种群遗传结构，这表明是最近的一次殖民化，独立于自然生物地理限制。中性检验和失配分布表明人口和空间种群突然扩张，这可能在更新世自然发生，也可能是由人为活动引发的现代殖民化的结果。
尽管印度扁卷螺是本研究的主要焦点，但我们的发现对于充分理解其在容纳复殖吸虫中的作用也可能具有重要意义。隐存物种复合体的存在、历史系统地理学模式以及印度 - 澳大利亚群岛最近的范围扩张为理解和监测寄生虫的潜在传播提供了有意义的见解。它对兽医和公共卫生问题做出了重大贡献。
