Cryptic diversity and gene flow among three African agricultural pests: Ceratitis rosa, Ceratitis fasciventris and Ceratitis anonae (Diptera, Tephritidae)

The ‘Ceratitis FAR complex’ is a species complex of African fruit flies (Diptera, Tephritidae) including the major agricultural pest Ceratitis rosa and the morphologically similar Ceratitis fasciventris and Ceratitis anonae. To resolve their intra- and interspecific genetic relationships and to estimate gene flow within this complex, we surveyed allelic variation at 16 microsatellite loci in 27 African populations of the three morphospecies. Interpopulation genetic distances and individual Bayesian assignments distinguished five genotypic clusters: two involving C. rosa (R1, R2; that may occur in sympatry), two involving C. fasciventris (F1, F2; with parapatric distributions) and one involving C. anonae (A). Intra- and interspecific patterns of genetic differentiation were not hierarchically structured and genetic differentiation between conspecific clusters (F1–F2 and R1–R2) was higher or comparable with differentiation between heterospecific clusters (e.g. F1-A or R2-A). In some cases, gene flow estimates among morphospecies or among heterospecific genotypic clusters were significantly different from zero, showing the lack of reproductive isolation. Genetic differentiation between genotypic clusters was partly supported by morphological differences observed a posteriori in male secondary sexual characters. These results suggest important revisions to current models of ecological niche requirements and invasion risk of the major agricultural pest C. rosa and provide a basis for a taxonomic re-interpretation of the FAR complex.

‘Ceratitis FAR复合体（Ceratitis FAR complex）’是一类隶属于双翅目（Diptera）实蝇科（Tephritidae）的非洲实蝇物种复合体，包含主要农业害虫玫瑰实蝇（Ceratitis rosa），以及形态上与其高度相似的拟橄榄实蝇（Ceratitis fasciventris）和阿氏实蝇（Ceratitis anonae）。为解析该复合体的种内与种间遗传关系，并估算其内部的基因流水平，我们对3个形态物种的27个非洲种群开展了16个微卫星（microsatellite）位点的等位基因变异检测。种群间遗传距离分析与个体贝叶斯（Bayesian）聚类归属分析共区分出5个基因型簇：2个对应玫瑰实蝇（R1、R2，二者可能呈同域分布）、2个对应拟橄榄实蝇（F1、F2，分布呈邻域格局），以及1个对应阿氏实蝇（A）。种内与种间的遗传分化模式并非呈层级结构；同物种内不同簇（F1–F2与R1–R2）间的遗传分化水平，高于或等同于异物种簇间的分化水平（例如F1–A或R2–A）。部分案例中，形态物种间或异物种基因型簇间的基因流估算值显著非零，表明二者间不存在完全的生殖隔离。基因型簇间的遗传分化，得到了后续观察到的雄性第二性征形态差异的部分支持。本研究结果表明，当前针对主要农业害虫玫瑰实蝇的生态位需求与入侵风险模型亟需重要修订，同时也为FAR复合体的分类学重新解读提供了科学依据。