Data from: Hybridization and adaptation to introduced balloon vines in an Australian soapberry bug

Contemporary adaptation of plant feeding insects to introduced hosts provides clear cases of ecologically based population divergence. In most cases the mechanisms permitting rapid differentiation are not well known. Here we study morphological and genetic variation associated with recent shifts by the Australian soapberry bug Leptocoris tagalicus onto two naturalized Neotropical balloon vines, Cardiospermum halicacabum and C. grandiflorum that differ in time since introduction. Our results show that these vines have much larger fruits than the native hosts (Whitewood tree –Atalaya hemiglauca– and Woolly Rambutan –Alectryon tomentosus–) and that bugs living on them have evolved significantly longer beaks and new allometries. Genetic analyses of mitochondrial haplotypes and amplified fragment length polymorphic (AFLP) markers indicate that the lineage of bugs on the annual vine C. halicacabum, the older introduction, is intermediate between the two subspecies of L. tagalicus found on native hosts. Moreover, where the annual vine and Whitewood tree co-occur together, the morphology and genomic composition of the bugs are similar to those occurring in allopatry. These results show that hybridization provided the genetic elements underlying the strongly differentiated ‘Halicacabum bugs’. In contrast, the bugs feeding on the recently introduced perennial balloon vine (C. grandiflorum) showed no evidence of admixture, and are genetically indistinguishable from the nearby populations on a native host.

植食性昆虫对引入宿主的当代适应性，为基于生态机制的种群分化提供了清晰的研究案例，但多数情况下支撑这类快速分化的分子机制仍未被充分阐明。本研究聚焦于澳洲肥皂草椿象（Leptocoris tagalicus）近期的宿主转移事件：该物种现已侵染两种新热带界归化气球藤——倒地铃（Cardiospermum halicacabum）与大花倒地铃（C. grandiflorum），二者的归化时间存在差异。研究结果显示，这两种气球藤的果实远大于其本土宿主——白木树（Atalaya hemiglauca）与毛叶红毛丹（Alectryon tomentosus）；取食这两种外来藤本的椿象，已演化出显著更长的喙部，并形成了全新的异速生长模式。针对线粒体单倍型与扩增片段长度多态性（amplified fragment length polymorphic, AFLP）标记的遗传分析表明，取食归化时间更早的一年生藤本C. halicacabum的椿象种群，其遗传位置介于本土宿主上的两个L. tagalicus亚种之间。此外，在一年生藤本与白木树同域分布的区域，椿象的形态与基因组组成与异域种群的个体高度相似。上述结果证实，杂交事件为分化显著的‘倒地铃椿象种群’提供了关键的遗传基础。与之形成对比的是，取食新近归化的多年生气球藤C. grandiflorum的椿象种群未表现出遗传混合的迹象，其遗传特征与周边本土宿主上的种群无显著差异。