The discovery of Iberobaeniidae (Coleoptera: Elateroidea): a new family of beetles from Spain, with immatures detected by environmental DNA sequencing

Abstract

The ongoing exploration of biodiversity and the implementation of new molecular tools continue to unveil hitherto unknown lineages. Here, we report the discovery of three species of neotenic beetles for which we propose the new family Iberobaeniidae. Complete mitochondrial genomes and rRNA genes recovered Iberobaeniidae as a deep branch in Elateroidea, as sister to Lycidae (net-winged beetles). Two species of the new genus Iberobaenia, Iberobaenia minuta sp. nov. and Iberobaenia lencinai sp. nov. were found in the adult stage. In a separate incidence, a related sequence was identified in bulk samples of soil invertebrates subjected to shotgun sequencing and mitogenome assembly, which was traced to a larval voucher specimen of a third species of Iberobaenia Iberobaenia shows characters shared with other elateroid neotenic lineages, including soft-bodiedness, the hypognathous head, reduced mouthparts with reduced labial palpomeres, and extremely small-bodied males without strengthening structures due to miniaturization. Molecular dating shows that Iberobaeniidae represents an ancient relict lineage originating in the Lower Jurassic, which possibly indicates a long history of neoteny, usually considered to be evolutionarily short-lived. The apparent endemism of Iberobaeniidae in the Mediterranean region highlights the importance of this biodiversity hotspot and the need for further species exploration even in the well-studied European continent.

Keywords: biodiversity; endemism; mitogenomes; molecular phylogeny; neoteny; soil arthropods.

Figure 1.

(a) Phylogenetic hypothesis of Elateroidea inferred from the four-gene BlastAlign dataset using maximum-likelihood optimality criterion. Iberobaenia represented by a four-gene chimera. (b) Relative species diversity of soft-bodied and completely sclerotized elateroid lineages. (c) Phylogenetic position and relative species diversity of neotenic and completely metamorphosing lineages. The numbers of species are taken from Bocak et al. [2,6]. (d) Maximum clade credibility ultrametric tree resulting from the Bayesian analysis of 13 mtDNA genes, LSU and SSU rRNA in the program Beast (8-partitions applied). (Online version in colour.)

Figure 2.

Morphology of Iberobaenia minuta sp. nov. (a–e, adult) and Iberobaenia sp. (f–h, larva). (a) General appearance, (b) thorax ventrally, (c) pronotum, (d) terminal abdominal segments, (e) male genitalia, (f) thorax and head ventrally, (g) abdomen ventrally, (h) head ventrally. Scale bars: 1.0 mm (a,b), 0.5 mm (g), 0.25 mm (c–f,h). (Online version in colour.)