Leasi Francesca, Andrade Sónia Cristina da Silva, Norenburg Jon
Department of Invertebrate Zoology, Smithsonian National Museum of Natural History, PO Box 37012, NMNH, Washington, DC, 20013-7012, USA.
Departamento de Genética e Biologia Evolutiva-IB, USP, São Paulo, SP, 05508-090, Brazil.
Mol Ecol. 2016 Mar;25(6):1381-97. doi: 10.1111/mec.13568. Epub 2016 Mar 6.
Most meiofaunal species are known to have a broad distribution with no apparent barriers to their dispersion. However, different morphological and/or molecular methods supported patterns of diversity and distribution that may be different among taxa while also conflicting within the same group. We accurately assessed the patterns of geographic distribution in actual genetic species of a marine meiofaunal animal model: Ototyphlonemertes. Specimens were collected from several sites around Europe, Northern and Central America, Southern America, Pacific Islands and Asia. We sequenced regions of two mitochondrial and two nuclear genes. Using single-gene, a concatenated data set, multilocus approaches and different DNA taxonomy methods, we disentangled the actual diversity and the spatial structures of haplotypes and tested the possible correlation between genetic diversity and geographic distance. The results show (i) the importance of using several genes to uncover both diversity and highlight phylogeographic relationships among species and that (ii) independent genetic evolutionary entities have a narrower distribution than morphological species. Moreover, (iii) a Mantel test supported a positive correlation between genetic and geographical distance. By sampling from the two sides of Isthmus of Panama, we were additionally able to identify lineage divergence times that are concordant with vicariance mechanisms caused by the geological closure of the seaway across the Isthmus. We therefore propose that in addition to distance, other geological and ecological conditions are also barriers to the dispersion of and gene flow in marine meiofaunal organisms.
大多数小型底栖动物物种的分布范围很广，其扩散没有明显障碍。然而，不同的形态学和/或分子方法所支持的多样性和分布模式在不同分类群之间可能不同，同时在同一类群内部也存在冲突。我们准确评估了一种海洋小型底栖动物模型——盲纽虫（Ototyphlonemertes）实际遗传物种的地理分布模式。样本采集自欧洲、北美洲北部和中部、南美洲、太平洋岛屿以及亚洲的多个地点。我们对两个线粒体基因区域和两个核基因区域进行了测序。使用单基因、串联数据集、多位点方法以及不同的DNA分类方法，我们厘清了实际的多样性和单倍型的空间结构，并测试了遗传多样性与地理距离之间可能存在的相关性。结果表明：（i）使用多个基因来揭示物种之间的多样性并突出系统发育地理关系非常重要；（ii）独立的遗传进化实体的分布范围比形态学物种更窄。此外，（iii）曼特尔检验支持了遗传距离与地理距离之间存在正相关。通过从巴拿马地峡两侧采样，我们还能够确定与因地峡处海道地质封闭导致的隔离机制相一致的谱系分歧时间。因此，我们提出除了距离之外，其他地质和生态条件也是海洋小型底栖生物扩散和基因流动的障碍。
