Molecular phylogeny and evolution of Calaphidinae (Hemiptera: Aphididae)

Calaphidinae is the second-largest subfamily in the family Aphididae. Despite their species diversity and some taxonomic controversy, no phylogenetic studies have been conducted on them thus far. Herein, we report the first molecular phylogeny of Calaphidinae and two related lineages, Phyllaphidinae and Saltusaphidinae, based on five genes (3418 bp) for 126 taxa. Maximum parsimony, maximum-likelihood and Bayesian inference phylogenetic analyses were performed on the multilocus dataset. Divergence time estimation, biogeographical reconstruction, ancestral host plant reconstruction and PhyloType analyses were performed to identify evolutionary trends in Calaphidinae. Our phylogenetic results lead to several conclusions: Phyllaphidinae is a sister group to Calaphidinae s.l.; Calaphidinae is paraphyletic with respect to the former "Saltusaphidinae"; the ingroup clade was subdivided into nine newly recognized lineages; and three subtribes of Calaphidinae (Monaphidina, Calaphdina and Panaphidina) and many genera were not recovered as monophyletic. A new classification is proposed with eight tribal divisions that reflect our phylogenetic results, including three new tribes (Pterocallidini trib.n., Pseudochromaphidini trib.n. and Shivaphidini trib.n.) and three new statuses (Saltusaphidini stat.n., Therioaphidini stat.n. and Myzocallidini stat.n.). The ancestral reconstruction results imply that the ingroup taxa's common ancestor originated in the Eastern Palaearctic and might have fed on Fagaceae in the Late Cretaceous. Later, multiple host shifts and an expanding geographical distribution led to the current species diversity of Calaphidinae. Our reconstructions suggest that species diversification cannot solely be explained by speciation via host shifts and that geographical isolation probably also played a key role. Our results provide new insight into the natural classification and history of the host plant associations and biogeography of Calaphidinae s.l.