The phylogeny and limits of Elateridae (Insecta, Coleoptera): Is there a common tendency of click beetles to soft-bodiedness and neoteny?

摘要

Phylogenetic relationships in Elateroidea were investigated using partial 18S and 28S rDNA and rrnl and cox1 mtDNA sequences with special interest in the phylogeny of Elateridae and the position of soft-bodied lineages Drilidae and Omalisidae that had been classified as families in the cantharoid lineage of Elateroidea until recently. Females in these groups are neotenic and almost completely larviform (Drilidae) or brachypterous (Omalisidae). The newly sequenced individuals of Elateridae, Drilidae, Omalisidae and Eucnemidae were merged with previously published datasets and analysed matrices include either 155 taxa with the complete representation of fragments or 210 taxa when some fragments were missing. The main feature of inferred phylogenetic trees was the monophyly of Phengodidae+Rhagophthalmidae+Omalisidae+Elateridae+Drilidae with Omalisidae regularly occupying a basal node in the group; Drilidae were embedded as a terminal lineage in the elaterid subfamily Agrypninae and soft-bodied Cebrioninae were a part of Elaterinae. The soft-bodied males and incompletely metamorphosed females originated at least three times within the wider Elateridae clade. Their atypical morphology has been considered as a result of long evolutionary history and they were given an inappropriately high rank in the previous classifications. The frequent origins of these modifications seem to be connected with modifications of the hormonal regulation of the metamorphosis. The superficial similarity with other soft-bodied lineages, such as Cantharidae, Lycidae, Lampyridae, Phengodidae and Rhagophthalmidae is supposed to be a result of homoplasious modifications of the ancestral elateroid morphology due to the incomplete metamorphosis. The results of phylogenetic analyses are translated in the formal taxonomic classification. Most Drilidae are placed in Elateridae as a tribe Drilini in Agrypninae, whilst Pseudeuanoma and Euanoma are transferred from Drilidae to Omalisidae. The subfamily Cebrioninae is placed in Elaterinae as tribes Cebrionini and Aplastini. Oxynopterini, Pityobiini and Semiotini are lowered from the subfamily rank to tribes and classified in Denticollinae.