Hamdan Breno, Pereira Anieli G, Loss-Oliveira Letícia, Rödder Dennis, Schrago Carlos G
Departamento de Genética, Universidade Federal do Rio de Janeiro, RJ, Brazil; Laboratório de Coleções Biológicas e Biodiversidade, Instituto Vital Brazil, Niterói, RJ, Brazil.
Departamento de Genética, Universidade Federal do Rio de Janeiro, RJ, Brazil.
Mol Phylogenet Evol. 2017 Nov;116:108-119. doi: 10.1016/j.ympev.2017.08.004. Epub 2017 Aug 10.
Recent hypotheses to explain tropical diversity involves the Neogene and Quaternary geoclimatic dynamics, but the absence of unambiguous data permitting the choice between alternative hypotheses makes a general theory for the origin of tropical biodiversity far to be achieved. The occurrence of Chironius snakes in well-defined biogeographical regions led us to adopt Chironius as a model to unveil patterns of vertebrate diversification in the Neotropics. Here, we used molecular markers and records on geographic distribution to investigate Chironius evolution and, subsequently, providing hints on diversification in the Neotropics. To avoid analyzing nominal species that do not constitute exclusive evolutionary lineages, we firstly conducted a species delimitation study prior to carrying out the species distribution modeling analysis. We generated 161 sequences of 12S, 16S, c-mos and rag2 for 15 species and 50 specimens, and included additional data from GenBank yielding a matrix of 137 terminals, and performed the following evolutionary analyses: inference of a concatenated gene tree, estimation of gene divergence times, inference of the coalescent-based phylogeny of Chironius, estimation of effective population sizes and modeling potential distribution of species across the last millennia. We tested for species boundaries within Chironius by implementing a coalescent-based Bayesian species delimitation approach. Our analyses supported the monophyly of Chironius, although our findings underscored cryptic candidate species in C. flavolineatus and C. exoletus. The inferred timetree suggested that Chironius snakes have evolved in the early Miocene (ca. 20.2Mya) and began to diversify from the late Miocene to the early Pliocene, values that are much older than previously reported. Following genetic divergence of virtually all extant Chironius species investigated, the effective sizes of the populations have expanded when compared to their MRCAs. The evolutionary and SDM data from C. brazili and C. diamantina provided additional evidence of the origin of species in the Neotropics. We argue that temperature, instead of altitude, has been the major driving factor in the evolution of both species, and thus we present a case for the consequences of global warming.
近期关于解释热带地区生物多样性的假说涉及新近纪和第四纪的地质气候动态，但由于缺乏明确的数据来在不同假说之间做出选择，使得热带生物多样性起源的通用理论远未达成。在明确界定的生物地理区域中出现的Chironius蛇类，促使我们将Chironius作为一个模型，以揭示新热带地区脊椎动物的多样化模式。在此，我们使用分子标记和地理分布记录来研究Chironius的进化，并随后为新热带地区的多样化提供线索。为避免分析不构成独立进化谱系的名义物种，我们在进行物种分布建模分析之前，首先开展了一项物种界定研究。我们为15个物种和50个标本生成了12S、16S、c-mos和rag2的161个序列，并纳入了来自GenBank的额外数据，形成了一个包含137个终端的矩阵，然后进行了以下进化分析：推断串联基因树、估计基因分歧时间、推断基于溯祖的Chironius系统发育、估计有效种群大小以及模拟过去几千年物种的潜在分布。我们通过实施基于溯祖的贝叶斯物种界定方法来检验Chironius内部的物种界限。我们的分析支持了Chironius的单系性，尽管我们的研究结果强调了黄纹Chironius和小斑Chironius中存在隐存候选物种。推断出的时间树表明，Chironius蛇类在中新世早期（约2020万年前）已经进化，并从中新世晚期到上新世早期开始多样化，这些时间比之前报道的要古老得多。在几乎所有被研究的现存Chironius物种发生遗传分歧之后，与它们的最近共同祖先相比，种群的有效大小有所扩大。来自巴西Chironius和钻石Chironius的进化和物种分布模型数据，为新热带地区物种的起源提供了额外证据。我们认为，温度而非海拔高度，一直是这两个物种进化的主要驱动因素，因此我们阐述了全球变暖的后果。
