A molecular phylogeny of Ceratophyllomorpha (Insecta: Siphonaptera): geographical distribution, origins, and host associations

From a taxonomic and systematic perspective, the order Siphonaptera is a neglected and overlooked group of insects. The classification of fleas is further hampered by a few classical taxonomic keys published over 40 years ago and, in many cases, they are not digitized and thus not easily accessible. More recently, molecular data have been utilized with great success in an attempt to resolve some of the higher level taxonomic uncertainties for Siphonaptera, but detailed phylogenetic studies of fleas are still scarce. Here we conduct a comprehensive phylogenetic and evolutionary review using 148 taxa within the infraorder Ceratophyllomorpha with 4689 aligned sites derived from seven different molecular markers. Bayesian phylogenetic analyses supported the monophyly of 34/48 genera (71%), and also supported the monophyly of most members within the Leptopsyllidae, Ceratophyllidae, and Ischnopsyllidae. The dated phylogeny constructed shows that diversification within the Ceratophyllomorpha dates back to ~23.1 Mya, and from this period onwards, the evolution of the fleas included herein was influenced by both host association and host distribution. The most common hosts of the Ceratophyllomorpha group were various families of rodents, with the exception of the Ischnopsyllidae, that was specific to the order Chiroptera. The rich extant Ceratophyllomorpha diversity is mainly confined to the Palaearctic region, and this geographic pattern was most evident for the family Leptopsyllidae. The present study emphasizes the need for a comprehensive taxonomic revision for the order Siphonaptera. Since the current taxonomic schemes are mainly based on morphology, future focus should be given to those species where no molecular data are available and where molecular data are scarce.