Integrated taxonomy, biology and biogeography of the Afrotropical genus Xyloctonus (Coleoptera, Curculionidae, Scolytinae)

Abstract

The peculiar Afrotropical bark beetle genus Xyloctonus Eichhoff, 1872 is revised and its biology described. Several unusual morphological features reflect adaptations to predator avoidance as they are highly exposed during mating externally on tree trunks and branches. Observations invariably indicate that males and females abandon the nest under bark at an early stage of progeny, the males already before eggs hatch, potentially engaging in subsequent additional matings. Most species have a clear preference for host plants in the plant family Sapotaceae. Although the genus is broadly distributed in forested parts of Africa, Madagascar and Mauritius, most species are found in the eastern part of this range. A Bayesian biogeographical analysis revealed a possible origin of the genus in Madagascar in the early Eocene, with subsequent colonisation of the southern African region in late Eocene. This contrasts with the closely-related xyloctonine genus Ctonoxylon Hagedorn, 1910, which is of western Congolian ancestry and more recently reached Madagascar multiple times during late Miocene. Two new species are described: Xyloctonus magnus sp. nov. from Madagascar and X. genieri sp. nov. from Burkina Faso. Synonyms are proposed for X. subcostatus Eggers, 1939 (= X. striatus Eggers, 1939) and X. scolytoides Eichhoff, 1872 (= X. latus Eggers, 1922). Identification to species is provided in a key illustrated with photographs of most species.