An extraordinary case of elytra loss in Coleoptera (Elateroidea: Lycidae): discovery and placement of the first anelytrous adult male beetle

Abstract

Insects are one of the few groups of animals that developed the ability of active flight. Such mobility allowed the group to successfully explore and thrive in nearly all kinds of ecological niches. At the same time, during the evolutionary history of insects, due to high costs of wing development, flight was lost independently in many groups. In beetles, the reduction or complete loss of hind wings has been reported in multiple lineages, especially in several extreme paedomorphic and larviform females, mainly in Elateroidea, in which not only the hind wings but also the elytra are lost. However, the complete absence of elytra in adult males was hitherto unknown, despite nearly half a million described species in Coleoptera. In this study, we report the discovery of Xenomorphon baranowskii gen. et sp. nov., the first completely anelytrous and wingless adult male beetle, belonging to the family Lycidae (Coleoptera: Elateroidea). Xenomorphon baranowskii is illustrated, described, and provisionally placed in Calopterini, based on our morphology-based phylogenetic analyses. We discuss the possible scenarios that could lead to such a rare event, when a beetle loses its elytra, and its evolutionary consequences.

Performance of tree-building methods using a morphological dataset and a well-supported Hexapoda phylogeny

“…We performed a series of classic nonparametric tree topology tests ( i.e ., paired-site tests sensu Felsenstein, 2004b ) that can be used in parsimony- and likelihood-based phylogenies ( Felsenstein, 2004b ; Goldman, Anderson & Rodrigo, 2000 ; Shimodaira, 2002 ), following a well-known similar approach used in many studies ( e.g ., Buckley, 2002 ; Černý & Simonoff, 2023 ; Ferreira et al, 2023 ; Schneider, 2007 ). Our topology tests included both parsimony- and likelihood-based tests to avoid any bias favouring any tested phylogenetic tree-building method.…”

When a key innovation becomes redundant: Patterns, drivers and consequences of elytral reduction in Coleoptera

“…Although females are more affected than males in the paedomorphic lineages, even the latter sometimes show more-or-less similar morphological modifications, including shortening or even loss of the elytra (Ferreira et al, 2023;Kusy et al, 2019). In Dexorinae, females are unknown but hypothesized to be paedomorphic.…”

“…In many cases, however, females are unknown and we can only hypothesise that they are also highly paedomorphic (for more information, see Kusy et al, 2019). Although females are more affected than males in the paedomorphic lineages, even the latter sometimes show more‐or‐less similar morphological modifications, including shortening or even loss of the elytra (Ferreira et al, 2023; Kusy et al, 2019). In Dexorinae, females are unknown but hypothesized to be paedomorphic.…”

“…In Lycinae, paedomorphic females are reported in Leptolycini and likely also occur in some Calopterini (Ferreira, 2020; Ferreira & Ivie, 2022; Miller, 1991). Ferreira et al (2023) recently described Xenomorphon baranowskii Ferreira et al from a high‐altitude region in Mexico, which represents a very rare case of anelytrous adult male in Coleoptera; the authors tentatively placed it in Calopterini. Lyropaeinae are the largest lycid group containing larviform females.…”

“…Ferreira et al (2023) recently described Xenomorphon baranowskii Ferreira et al from a highaltitude region in Mexico, which represents a very rare case of anelytrous adult male in Coleoptera; the authors tentatively placed it in Calopterini. Lyropaeinae are the largest lycid group containing larviform females.…”