Newly sequenced genomes reveal patterns of gene family expansion in select dragonflies (Odonata: Anisoptera)

Abstract Gene family evolution plays a key role in shaping patterns of biodiversity across the tree of life. In Insecta, adaptive gene family turnover has broadly been tied to vision, diet, pesticide resistance, immune response, and survival in extreme environments. Patterns of gene family evolution are of particular interest in Odonata (dragonflies and damselflies), which represents the first lineage to fly, and one of the most exceptional groups of predators. Previous work in Odonata found expansions of opsin genes are correlated with the diversification of the herbivorous insects that Odonata prey upon, but general trends in gene family turnover have not been studied in this order. Here, we show that two families of suborder Anisoptera (dragonflies), Libellulidae and Petaluridae, have expanded gene repertoire related to their unique life history and diversification patterns. These results are an important step towards understanding why Libellulidae is, generally, a species-rich family of short-lived species that are highly tolerant to poor water quality, while Petaluridae is a species-poor family of habitat and behavioral specialists. Specifically, Libellulidae share expanded gene families related to immune response, desiccation response, and processing of free radicals, which all potentially enable many Libellulidae to inhabit low-quality water bodies. Likewise, Petaluridae show unique patterns of gene turnover in gene families implicated in sensory perception, which could be tied to the unique semi-terrestrial lifestyle of the nymphs of this family. Furthermore, Odonata as a whole has a gene turnover rate that is an order of magnitude smaller than other studied insect orders, potentially contributing to the relatively low species diversity in the order Odonata compared to other insects. These results offer important hypotheses for the consideration of evolutionary drivers across Insecta.