Beetles and lichens: tracing the origins and evolution of lichenophagy within the darkling beetle tribe Helopini (Coleoptera: Tenebrionidae)

Abstract

Abstract Although the complex evolutionary history of lichen-forming fungi has gained considerable attention, particularly regarding the long-debated role of these organisms in shaping early terrestrial ecosystems, the evolution of lichenivory and its potential impact on the diversification of lichenophages have been largely neglected. With > 800 described species worldwide and a broad geographical distribution, the tribe Helopini (Coleoptera: Tenebrionidae) represents a diverse, yet poorly studied, group of predominantly lichenophagous beetles. Using a dataset of 52 ingroup taxa and five gene fragments, a first phylogenetic hypothesis of the tribe was generated, which was subsequently used for reconstructing the ancestral state of the trophic and habitat associations of the beetles and for estimating a time frame of diversification. Our phylogenetic reconstruction sheds light on the higher-level systematics of the tribe, supporting the current subtribal division of the group while also providing a framework for understanding the intergeneric relationships within subtribes. The results also indicate an Early Cretaceous origin of the tribe, highlighting the close association between Helopini and lichen-forming fungi since the emergence of the group. Nevertheless, at least seven independent switches from lichenophagy to alternative feeding habits have occurred since the middle Eocene, which can be linked temporally to transitions from forests to open habitats.