Systematics of Nitidulinae (Coleoptera:Nitidulidae): phylogenetic relationships, convexity and the origin of phallalophagy

Abstract

Nitiduline beetle genera of the Cyllodes complex arestudied in the context of a phylogenetic analysis of 19 ingroup and eightoutgroup taxa and 63 characters derived from adult morphology and hostrelationship. In this analysis, the Cyllodes complex isshown to be monophyletic. By eliminating the problematic taxonCamptodes and a priori weightingof the presence/absence of procoxal rests, two monophyletic taxa areobtained within the Cyllodes complex(Cyllodes and Oxycnemus groups). Aphylogenetic analysis of 13 terminal taxa represented by larval and adultsemaphoronts shows a monophyletic Cyllodes complex inone of two trees. The Cyllodes complex is formallyrecognised as Cyllodini Everts, containing two or more monophyletic groupsthat are recognised on an informal basis. The Oxycnemusgroup is well supported and may include the enigmatic genusCamptodes. Taxonomic actions include two synonymiesunder Apsectochilus Reitter (=Meoncerus Sharp, syn. nov.; =Lordyrops Reitter, syn. nov.) and type speciesdesignations for Neotropical genera described by David Sharp(Apsectochilus, Eusphaerius,Mecyllodes, and Somatoxus).Carinocyllodes, gen. nov. (type species:Eusphaerius lubricus Leschen & Carlton) is describedand includes two additional species (C. belli, sp. nov.and C. depressus, sp.nov.).

Convexity is a character complex in nitidulids, and must be partitioned forphylogenetic reconstruction and character analysis. Two classes of charactervariation (dependent and independent) are discussed with regard to theevolution of convexity in the context of cladograms. A highly convex form withthe capability to roll into a ball by tucking the head beneath the prothoraxhas evolved at least one or more times in Nitidulidae and several times inunrelated beetle families.

Fungal host-use patterns are highly concordant with the phylogenetic branchingpattern in Cyllodini. Most members are associated with large-bodiedBasidiomycetes, with the exception of Camptodes whichoccurs on flowers and develops in rotten vegetation. Most species of theOxycnemus group are restricted to Phallales, an obligatehost pattern that is old relative to those associations in the remainingCyllodini that occur on other fungi. Another significant shift occurred fromphallalophagy to phytophagy if the hypothesis is accepted thatCamptodes is a member of theOxycnemus group.