Molecular evidence places the swallow bug genus Oeciacus Stal within the bat and bed bug genus Cimex Linnaeus (Heteroptera: Cimicidae)

The genera Cimex Linnaeus and Oeciacus Stal (Heteroptera: Cimicidae) are common haematophagous ectoparasites of bats or birds in the Holarctic region. Both their phylogenetic relationship and the systematics of the entire family previously were based on data from morphology and host relationships. Relationships among nine species of the genus Cimex and three species of the genus Oeciacus were analysed here using two mitochondrial and three nuclear genes. Cimex was shown to be paraphyletic with respect to Oeciacus. Oeciacus is thus proposed as a synonym of Cimex. The characteristic phenotype of Oeciacus results from the specific host association with different species of swallows (Hirundinidae). The morphological characters that have been used as diagnostic for the genera were shown to be valid and can be further used for determination at species level. The present analyses recovered the four traditional morphologically defined species groups of the genus Cimex. However, their relationships were poorly resolved - only the C. hemipterus group showed a well-supported relationship to the C. pipistrelli group. The molecular differentiation within the Palaearctic C. pipistrelli and the Nearctic C. pilosellus species groups correlates with their karyotype differentiation. Furthermore, the analyses suggest poly- or paraphyly of the former genus Oeciacus. Either way this indicates there is a large amount of host-associated phenotypic convergence in either bat- or bird-associated groups of species. The probability of host choice and subsequent switch in Cimicidae are discussed and possible scenarios of the evolution of host association in species of Cimex are suggested.