Restricted Gene Flow among Lineages of <i>Thrips tabaci</i> Supports Genetic Divergence Among Cryptic Species Groups

Knowledge of the relative influence of population- versus species-level genetic variation is important to understand patterns of phenotypic variation and ecological relationships that exist among and within morphologically indistinguishable cryptic species and subspecies. In the case of cryptic species groups that are pests, such knowledge is also essential for devising effective population management strategies. The globally important crop pest Thrips tabaci is a taxonomically difficult group of putatively cryptic species. This study examines population genetic structure of T. tabaci and reproductive isolation among lineages of this species complex using microsatellite markers and mitochondrial COI sequences. Overall, genetic structure supports T. tabaci as a cryptic species complex, although limited interbreeding occurs between different clonal groups from the same lineage as well as between individuals from different lineages. These results also provide evidence that thelytoky and arrhenotoky are not fixed phenotypes among members of different T. tabaci lineages that have been generally associated with either reproductive mode. Possible biological and ecological factors contributing to these observations are discussed.明晰种群水平与物种水平遗传变异的相对影响，对于理解形态上难以区分的隐存种（cryptic species）及亚种内部和之间存在的表型变异模式与生态关系至关重要。对于作为害虫的隐存种群类群而言，此类认知对于制定有效的种群管理策略同样不可或缺。全球重要的农作物害虫烟蓟马（Thrips tabaci）是一类分类学上较为棘手的疑似隐存种群类群。本研究借助微卫星标记与线粒体COI序列，解析了烟蓟马的种群遗传结构，以及该物种复合群内不同演化支之间的生殖隔离情况。总体而言，种群遗传结构支持烟蓟马属于隐存种复合群这一结论，尽管同一演化支内的不同克隆群之间，以及不同演化支的个体之间，均存在有限的杂交繁殖现象。本研究结果还证实，通常分别与两种生殖模式相关联的不同烟蓟马演化支类群中，产雌孤雌生殖（thelytoky）与产雄孤雌生殖（arrhenotoky）并非固定的表型特征。本研究对可能促成上述观测结果的生物学与生态学因素展开了讨论。