To be or not to be a tibial comb: A discussion on the (past) use of tibial armature in tribal/subtribal organization in Cholevinae (Coleoptera: Leiodidae)

Abstract

Detailed studies of microstructure has recently been shown to provide phylogenetic signals at several supraspecific levels within leiodid coleopterans, as well as in other insects. The tribe Ptomaphagini (Leiodidae: Cholevinae), with a Holarctic-Neotropical-Oriental distribution, has been characterized, among other things, by having a comb of equal-sized, flat spines around the apex of the tibiae of all legs, with a row of spines extending along the outer edge of the protibiae in the subtribes Baryodirina and Ptomaphaginina (but not in Ptomaphagina). A pattern similar to the one in Ptomaphaginina also occurs in the Neotropical cholevine tribe Eucatopini, and this has been used to indicate a phylogenetic relationship between the two tribes (but recent phylogenetic studies have not supported such a close relationship). We here review and revise the presence and structure of periapical (here called an ‘apical crown’) and marginal (here called an ‘external comb’) combs of spines on tibiae in Ptomaphagini, using other cholevines (with and without apical tibial combs) for comparison. We find a phylogenetic signal in an apical crown of tibial spines not interrupted at the outer spur, which seems to be an additional synapomorphy of Ptomaphagini, differing from the pattern in Eucatopini and remaining cholevines with an apical comb of spines, in which the comb is interrupted. We highlight differences not previously noticed between the apical protibial armature of Ptomaphaginina and Eucatopini.