Molecular phylogeny reveals the gradual evolutionary transition to soft-bodiedness in click-beetles and identifies sub-Saharan Africa as a cradle of diversity for Drilini (Coleoptera: Elateridae)

Abstract

Drilini are soft-bodied predatory click-beetles (Elateridae: Agrypninae) with incompletely metamorphosed females. Due to divergent morphology, their classification has been contentious. We present the first densely sampled molecular phylogeny of Drilini based on nuclear and mitochondrial markers. Altogether, 44 species, representing all genera, were analysed using maximum likelihood and the Bayesian approach. Molecular analyses recovered five major clades that were also well supported by morphology. Afrotropical lineages mark deep splits. Most Palearctic species belong to a terminal clade. A few species of the predominantly Afrotropical Selasia are distributed from Arabia up to the Himalayas and Thailand. The origin of Drilini is dated to the Late Eocene (~35.5 Mya) and rapid radiation is identified from the Eocene/Oligocene to the Middle Miocene. We describe the gradual transformation of male morphological traits, e.g. the level of sclerotization, structure of mouthparts, loss of the thoracic interlocking mechanism, shortened elytra and expanded larviform abdomen. Five new genera, Austroselasia, Habeshaselasia, Illubaboria, Malacodrilus and Mashaselasia are proposed. Latoselasia, previously a subgenus of Wittmerselasia, is elevated to the genus rank. Five new species, Habeshaselasia nekemtensis, H. illubaborensis, Illubaboria bicolor, Malacodrilus hajeki and Mashaselasia aethiopica are described.

Hidden diversity in the Brazilian Atlantic rainforest: the discovery of Jurasaidae, a new beetle family (Coleoptera, Elateroidea) with neotenic females

“…The discovery of Jurasaidae and their placement in the basal Elateroidea shed new light on the evolution of neoteny in this beetle superfamily. Neoteny in Elateroidea has long been a widely studied phenomenon 19,21 , and recent studies repeatedly confirmed that it originated several times not only within the superfamily but also within several distantly related families 14,20,22,23,29 . Elateroidea are divided into the "basal grade" with mostly hard-bodied groups with only Omethidae and Jurasaidae having a soft body, and the robustly supported clade of "higher elateroids" which contains predominantly fully sclerotized click-beetles and the vast majority of soft-bodied lineages 13 .…”

“…Not only females, but also males in Jurasaidae, present interesting morphological modifications connected with soft-bodiedness and neoteny. In Elateroidea, divergence in the abdominal morphology represents a continuous scale from five ventrites of which all or at least some are connate (the majority of the well-sclerotized elateroids) through various intermediate stages to seven or eight ventrites, which are all free and connected by extensive intersegmental membranes (majority of the soft-bodied lineages) 29 . Jurasaidae males represent an intermediate form; their abdomen is soft and with five free ventrites (Figs.…”

Congruence Between Molecular Data and Morphology: Phylogenetic Position of Senodoniini (Coleoptera: Elateridae)

“…Recent studies showed that the molecular analyses may help to understand the phylogenetic relationships of the taxonomically problematic groups in Elateridae [4,5,6,37,38]. Here we used for the first time the combination of nuclear and mitochondrial markers to infer the phylogenetic position of the currently defined Senodoniini (i.e., Senodonia and Sossor ).…”

Unlocking the mystery of the mid-Cretaceous Mysteriomorphidae (Coleoptera: Elateroidea) and modalities in transiting from gymnosperms to angiosperms

“…Recent molecular phylogenetic analyses show that none of the previously defined superfamilies are monophyletic, and both well-sclerotized and soft-bodied lineages are present in the early-branching groups (Artematopodidae, Omethidae, Cerophytidae, Jurasaidae, Eucnemidae, Throscidae and Brachypsectridae) as well as in the so-called "higher Elateroidea" (Lycidae, Iberobaeniidae, Lampyridae, Cantharidae, Phengodidae, Rhagophthalmidae, and Elateridae including Drilini, Cebrionini, Omalisinae, and Plastocerinae) 10 , 24 , 26 , 30 – 32 . Apparently, the soft-bodied condition originated multiple times within Elateroidea 24 , and the transitions from a completely to a poorly sclerotized body include various changes in external morphology, such as the loss of interlocking devices, reduction of the prosternum and mesoventrite, and expression of basal abdominal sternites as ventrites (for a review, see 27 ). The independent origins, together with the different degrees of these traits in various elateroid lineages, cause problems in phylogenetic analyses based on morphology alone 22 .…”

“…The phylogenetic relationships within Elateriformia, as well as within Elateroidea and Byrrhoidea, are far from fully understood, despite the effort of numerous recent morphological and molecular-based studies 22 – 26 . Moreover, the morphology of taxa within this lineage should be treated carefully when establishing a classification, attributable to the independent evolutionary origins of the soft-body condition, neoteny and other confounding traits within the encompassing clade 24 – 27 .…”