Departamento de Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, IEGEBA (CONICET-UBA), Ciudad Autónoma de Buenos Aires, Argentina.
Mol Phylogenet Evol. 2013 Sep;68(3):644-56. doi: 10.1016/j.ympev.2013.04.011. Epub 2013 Apr 25.
Population genetic theory shows that asexual organisms may evolve into species, which behave as independent evolutionary units. As a result, they form genotypic clusters separated by deep gaps due to geographic isolation and/or divergent selection. Identification of several genetically divergent groups of weevils embodied in the nominal species Naupactus cervinus deserves further study, in order to test if these lineages are evolving independently. In the present paper we tested if the parthenogenetic weevil N. cervinus, native to South America and broadly distributed throughout the world, contains more than one evolutionary unit. For this purpose, we applied three different approaches, a multilocus phylogenetic analysis, the GMYC approach and the K/θ method. We accomplished these analyses through a survey of mitochondrial (COI and COII genes) and nuclear (ITS1 sequence) genetic variation and morphometric analysis in a sample which included individuals from different locations within the native geographic range of N. cervinus. In addition, we compared the divergence accumulated in this species with that in another weevil of the same tribe (Naupactini) showing identical reproductive mode to see if similar levels of morphological variation matches similar levels of genetic divergence. We report the presence of two independent evolutionary units living in sympatry in forest areas. The incongruence between mitochondrial and nuclear datasets analyzed herein reflects incomplete lineage sorting of the nuclear marker and different evolutionary rates between genomes. Ecological divergence driven by natural selection (sympatry) or secondary contact after geographic isolation (allopatry) might explain the deep gaps in mitochondrial phylogenies. Instead, Wolbachia infection was ruled out as a causal factor for such differentiation. We conclude that N. cervinus is probably a species complex with at least two well differentiated lineages that would represent a cluster of species in statu nascendi.
种群遗传理论表明，无性生物可能进化成表现为独立进化单位的物种。因此，它们形成了由于地理隔离和/或分歧选择而形成的由深沟隔开的基因型聚类。在名义物种 Naupactus cervinus 中鉴定出的几个遗传上不同的象鼻虫群值得进一步研究，以检验这些谱系是否在独立进化。在本文中，我们测试了原产于南美洲并广泛分布于世界各地的单性生殖象鼻虫 N. cervinus 是否包含一个以上的进化单位。为此，我们应用了三种不同的方法，即多点系统发育分析、GMYC 方法和 K/θ 方法。我们通过对来自 N. cervinus 原生地理范围内不同地点的个体进行线粒体（COI 和 COII 基因）和核（ITS1 序列）遗传变异和形态测量分析，并结合形态测量分析，完成了这些分析。此外，我们比较了该物种与具有相同生殖模式的另一类象鼻虫（Naupactini）积累的分化程度，以确定类似的形态变异程度是否与类似的遗传分化程度相匹配。我们报告了两个独立的进化单位在森林地区共生的存在。本文分析的线粒体和核数据集之间的不一致反映了核标记不完全谱系分选和基因组之间不同的进化速度。由自然选择（同域）或地理隔离后二次接触（异域）驱动的生态分化可能解释了线粒体系统发育中的深沟。相反，沃尔巴克氏体感染被排除为这种分化的因果因素。我们得出结论，N. cervinus 可能是一个具有至少两个分化良好谱系的物种复合体，代表了处于萌芽状态的物种群。
