Lima Francoise D, Strugnell Jan M, Leite Tatiana S, Lima Sergio M Q
Department of Botany and Zoology, Universidade Federal do Rio Grande do Norte, Natal, Rio Grande do Norte, Brazil.
Centre for Sustainable Tropical Fisheries and Aquaculture, James Cook University, Townsville, Queensland, Australia.
PeerJ. 2020 Mar 27;8:e8691. doi: 10.7717/peerj.8691. eCollection 2020.
The uplift of the Isthmus of Panama (IP) created a land bridge between Central and South America and caused the separation of the Western Atlantic and Eastern Pacific oceans, resulting in profound changes in the environmental and oceanographic conditions. To evaluate how these changes have influenced speciation processes in octopods, fragments of two mitochondrial (Cytochrome oxidase subunit I, COI and 16S rDNA) and two nuclear (Rhodopsin and Elongation Factor-1α, EF-1α) genes were amplified from samples from the Atlantic and Pacific oceans. One biogeographical and four fossil calibration priors were used within a relaxed Bayesian phylogenetic analysis framework to estimate divergence times among cladogenic events. Reconstruction of the ancestral states in phylogenies was used to infer historical biogeography of the lineages and species dispersal routes. The results revealed three well-supported clades of transisthmian octopus sister species pair/complex (TSSP/TSSC) and two additional clades showing a low probability of species diversification, having been influenced by the IP. Divergence times estimated in the present study revealed that octopod TSSP/TSSC from the Atlantic and Pacific diverged between the Middle Miocene and Early Pliocene (mean range = 5-18 Ma). Given that oceanographic changes caused by the uplift of the IP were so strong as to affect the global climate, we suggest that octopod TSSP/TSSC diverged because of these physical and environmental barriers, even before the complete uplift of the IP 3 Ma, proposed by the Late Pliocene model. The results obtained in this phylogenetic reconstruction also indicate that the octopus species pairs in each ocean share a recent common ancestor from the Pacific Ocean.
巴拿马地峡的隆起在中美洲和南美洲之间形成了一座陆桥，并导致了西大西洋和东太平洋的分离，从而引发了环境和海洋条件的深刻变化。为了评估这些变化如何影响八腕目动物的物种形成过程，从大西洋和太平洋的样本中扩增了两个线粒体基因片段（细胞色素氧化酶亚基I，COI和16S rDNA）和两个核基因片段（视紫红质和延伸因子-1α，EF-1α）。在宽松的贝叶斯系统发育分析框架内，使用了一种生物地理和四种化石校准先验来估计分支事件之间的分歧时间。通过系统发育树中祖先状态的重建来推断谱系的历史生物地理学和物种扩散路线。结果揭示了三个得到充分支持的跨地峡章鱼姐妹物种对/复合体（TSSP/TSSC）分支，以及另外两个显示物种多样化可能性较低的分支，它们受到了巴拿马地峡的影响。本研究估计的分歧时间表明，来自大西洋和太平洋的八腕目TSSP/TSSC在中新世中期和上新世早期之间发生了分歧（平均范围=5-18 Ma）。鉴于巴拿马地峡隆起引起的海洋学变化如此强烈，以至于影响了全球气候，我们认为八腕目TSSP/TSSC的分歧是由于这些物理和环境障碍，甚至早于上新世晚期模型提出的3 Ma巴拿马地峡完全隆起之前。在这个系统发育重建中获得的结果还表明，每个海洋中的章鱼物种对都有一个来自太平洋的最近共同祖先。
