Insect-bacteria parallel evolution in multiple-co-obligate-aphid association: a case in Lachninae (Hemiptera: Aphididae)

Abstract

Parallel phylogenies between aphid and its obligate symbiont Buchnera are hot topics which always focused on aphid lower taxonomic levels. Symbionts in the subfamily Lachninae are special. Buchnera in many lachnine species has undergone functional and genome size reduction that was replaced by other co-obligate symbionts. In this study, we constructed the phylogenetic relationships of Lachninae with a combined dataset of five genes sequenced from Buchnera to estimate the effects of a dual symbiotic system in the aphid-Buchnera cospeciation association. The phylogeny of Buchnera in Lachninae was well-resolved in the combined dataset. Each of the genera formed strongly supported monophyletic groups, with the exception of the genus Cinara. The phylogeny based on sequences from Buchnera was divided into five tribes according to the clades of the Lachninae hosts tree, with the phylogenies of Buchnera and Lachninae being generally congruent. These results first provided evidence of parallel evolution at the aphid subfamily level comprehensively and supported the view that topological congruence between the phylogenies of Buchnera and Lachninae would not be interfered with the other co-obligate symbionts, such as Sarretia, in aphid-entosymbiont association. These results also provided new insight in understanding host-plant coevolution in lachnine lineages.

Figure 1

ML phylogram of Buchnera based on the combined dataset. The sequences of Buchnera species are represented by the names of their host species. The outgroup strains are designated by the names of the bacteria. The three numbers near nodes refer to ML bootstrap support, Bayesian posterior probability, and MP bootstrap support, respectively.

Figure 2

Cophylogeny of aphid and Buchnera from Jane at the generic level, with the reconciled trees based on the molecular-based aphid tree and the combined genes Buchnera tree. Blue and black lines indicate the phylogenies of the Buchnera and aphids, respectively. Hollow red circles indicate cospeciation events; solid red and yellow circles indicate duplications; arrows indicate host switch events; dotted lines indicate loss events.

Figure 3

Cophylogeny of aphid and Buchnera from Jane at the tribe level with the reconciled trees based on the molecular-based aphid tree and the combined genes Buchnera tree: (A) Stomaphidini; (B) Tramini + Tuberolachnini; (C) Lachnini; (D) Eulachini. Blue and black lines indicate the phylogenies of the Buchnera and aphids, respectively. Hollow red circles indicate cospeciation events; solid red and yellow circles indicate duplications; arrows indicate host switch events; dotted lines indicate loss events.