Phylogeny of the flea beetles (Galerucinae: Alticini) from anchored phylogenomics, a new tribe of Galerucinae, and diagnostic insights

The flea beetles (tribe Alticini) are a major component of the global leaf beetle fauna, comprising 601 genera and approximately 10 000 species, and many plant pests. The internal relationships and monophyly of this group remain largely unresolved, with weak taxonomic stability, poor specimen identification capacity and little biological understanding above the generic level. Phylogenomic approaches could solve these and other longstanding taxonomic problems by incorporating vastly more evidence. In this study we generated a genomic dataset using Anchored Hybrid Enrichment (AHE) for 54 genera of Alticini, 16 genera of Galerucini, and 40 other Chrysomelidae genera to test the monophyly of flea beetles, of named and informal genus groups, and examine the utility of characters used to define and group genera.

Maximum likelihood and coalescent phylogenetic analyses produced well-resolved and overall congruent topologies. Notably, Synetinae was found as sister to Cassidinae + Eumolpinae + Lamprosomatinae + Cryptocephalinae, supporting its recognition as a valid subfamily. Within Galerucinae, Aulacothorax Boheman was found to represent a lineage sister to Galerucini + Alticini (each monophyletic), for which we describe new tribe Aulacothoracini. Galerucini and Alticini are reciprocally monophyletic following transfers of several genera. Our work recovered multiple evolutionary origins of jumping hind legs in Galerucinae, making morphological diagnosis of both Alticini and Galerucini difficult. Our analyses provided some phylogenetic resolution within Alticini, but character mapping shows that morphological diagnosis remain elusive. We discuss what will be needed to establish robust subtribal classifications within Galerucini and Alticini.