Department of Entomology, University of Georgia, Athens, GA 30602, USA.
Syst Biol. 2010 Mar;59(2):162-84. doi: 10.1093/sysbio/syp089. Epub 2009 Dec 14.
Species delimitation has been invigorated as a discipline in systematics by an influx of new character sets, analytical methods, and conceptual advances. We use genetic data from 68 markers, combined with distributional, bioclimatic, and coloration information, to hypothesize boundaries of evolutionarily independent lineages (species) within the widespread and highly variable nominal fire ant species Solenopsis saevissima, a member of a species group containing invasive pests as well as species that are models for ecological and evolutionary research. Our integrated approach uses diverse methods of analysis to sequentially test whether populations meet specific operational criteria (contingent properties) for candidacy as morphologically cryptic species, including genetic clustering, monophyly, reproductive isolation, and occupation of distinctive niche space. We hypothesize that nominal S. saevissima comprises at least 4-6 previously unrecognized species, including several pairs whose parapatric distributions implicate the development of intrinsic premating or postmating barriers to gene flow. Our genetic data further suggest that regional genetic differentiation in S. saevissima has been influenced by hybridization with other nominal species occurring in sympatry or parapatry, including the quite distantly related Solenopsis geminata. The results of this study illustrate the importance of employing different classes of genetic data (coding and noncoding regions and nuclear and mitochondrial DNA [mtDNA] markers), different methods of genetic data analysis (tree-based and non-tree based methods), and different sources of data (genetic, morphological, and ecological data) to explicitly test various operational criteria for species boundaries in clades of recently diverged lineages, while warning against over reliance on any single data type (e.g., mtDNA sequence variation) when drawing inferences.
物种界定作为系统学中的一个学科，由于新的特征集、分析方法和概念的涌现而得到了复兴。我们使用来自 68 个标记的遗传数据，结合分布、生物气候和颜色信息，假设广泛且高度多变的指名红火蚁种 Solenopsis saevissima 内进化独立谱系（物种）的边界，该种是包含入侵害虫以及生态和进化研究模型物种的物种组的成员。我们的综合方法使用多种分析方法来依次测试种群是否符合作为形态上隐匿物种候选资格的特定操作标准（偶然属性），包括遗传聚类、单系性、生殖隔离和独特生态位空间的占据。我们假设，名义上的 S. saevissima 至少包含 4-6 个以前未被识别的物种，包括几个近缘种，它们的边缘分布暗示了内在的交配前或交配后障碍的发展，以阻止基因流动。我们的遗传数据还表明，S. saevissima 中的区域遗传分化受到与其他在同域或边缘域发生的名义物种杂交的影响，包括亲缘关系较远的 Solenopsis geminata。这项研究的结果说明了在最近分化的谱系的类群中明确测试物种边界的各种操作标准时，使用不同类别的遗传数据（编码和非编码区域以及核和线粒体 DNA[mtDNA]标记）、不同的遗传数据分析方法（基于树和非树的方法）以及不同的数据来源（遗传、形态和生态数据）的重要性，同时警告不要在得出推论时过度依赖任何单一数据类型（例如 mtDNA 序列变异）。
