Fundación para el Estudio de Especies Invasivas (FuEDEI), Hurlingham, Buenos Aires, Argentina.
Instituto de Ecología Genética y Evolución de Buenos Aires (IEGEBA), Departamento de Ecología Genética y Evolución, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina.
PLoS One. 2019 Jul 25;14(7):e0220366. doi: 10.1371/journal.pone.0220366. eCollection 2019.
Hypogeococcus pungens, a mealybug native of southern South America, is devastating native cacti in Puerto Rico and threatening cactus diversity in the Caribbean, and potentially in Central and North America. The taxonomic status of H. pungens is controversial since it has been reported feeding not only on Cactaceae but also on other plant families throughout its distribution range. However, in Australia, where the species had been exported from Argentina to control weedy American cacti, it was never found on host plants other than Cactaceae. These conflicting pieces of evidence not only cast doubt on the species identity that invaded Puerto Rico, but also have a negative impact on the search for natural enemies to be used in biological control programs against this pest. Here we present reproductive incompatibility and phylogenetic evidences that give support to the hypothesis that H. pungens is a species complex in which divergence appears to be driven by the host plants. The nuclear EF1α and 18S and the mitochondrial COI genes were used as markers to evaluate the phylogenetic relationships among H. pungens populations collected in Argentina, Australia and Puerto Rico feeding on Cactaceae and/or Amaranthaceae. Additionally, we conducted reciprocal crosses between mealybugs from both hosts. Species delimitation analysis revealed two well-supported putative species within H. pungens, one including mealybugs feeding on Amaranthaceae (H. pungens sensu stricto), and a new undescribed species using Cactaceae as hosts. Additionally, we found asymmetric reproductive incompatibility between these putative species suggesting recent reproductive isolation. The Bayesian species delimitation also suggested that the Australian mealybug population may derive from another undescribed species. Overall, the patterns of genetic differentiation may be interpreted as the result of recent speciation events prompted by host plant shifts. Finally, the finding of a single haplotype in the Puerto Rico population suggests only one invasive event. We still need to identify the geographical origin of the pest in order to enable the use of biological control to reduce the threat to cacti diversity in the Caribbean.
刺角隐唇瓢虫原产于南美洲南部，正在摧毁波多黎各的本地仙人掌，并威胁到加勒比地区、可能还有中美洲和北美洲的仙人掌多样性。由于刺角隐唇瓢虫的报道不仅在其分布范围内以仙人掌科为食，而且还以其他植物科为食，因此其分类地位存在争议。然而，在澳大利亚，该物种已从阿根廷出口用于控制杂草丛生的美洲仙人掌，但从未在仙人掌科以外的宿主植物上发现过。这些相互矛盾的证据不仅对入侵波多黎各的物种身份提出了质疑，而且对寻找用于该害虫生物防治计划的天敌也产生了负面影响。在这里，我们提出了生殖不相容性和系统发育证据，支持刺角隐唇瓢虫是一个物种复合体的假设，其中分化似乎是由宿主植物驱动的。核 EF1α 和 18S 以及线粒体 COI 基因被用作标记，以评估在阿根廷、澳大利亚和波多黎各收集的以仙人掌科和/或苋科为食的刺角隐唇瓢虫种群之间的系统发育关系。此外，我们还在来自这两个宿主的粉蚧之间进行了正反交。物种划分分析显示，刺角隐唇瓢虫内存在两个支持良好的假定种，一个包括以苋科为食的粉蚧（刺角隐唇瓢虫狭义种），另一个新的未描述种以仙人掌科为宿主。此外，我们还发现这两个假定种之间存在不对称的生殖不相容性，表明最近发生了生殖隔离。贝叶斯物种划分也表明，澳大利亚粉蚧种群可能源自另一个未描述的物种。总的来说，遗传分化的模式可以解释为宿主植物转移引发的新物种形成事件的结果。最后，波多黎各种群中发现的单一单倍型表明只有一次入侵事件。为了利用生物防治来降低对加勒比地区仙人掌多样性的威胁，我们仍需确定该害虫的地理起源。
