In good form: Morphological adaptations to burrowing lifestyles in cockroaches (Dictyoptera: Blattodea)

Abstract Investigating forms specialized for their ecology (i.e. ecomorphs) is a major theme in ecology and evolution. Among the remarkable ecomorphs, those associated with fossorial habits have received increasing attention in vertebrates, but less so in invertebrates. Here, we focus on cockroaches, insects whose burrowing ecomorphs have long been observed but never formally investigated at a large taxonomic scale. Our goal is to characterize different cockroach ecomorphs, with a particular focus on fossorial organisms in the broadest sense, that is, including cockroaches digging galleries and feeding in deadwood. The study of these wood‐eating species is particularly important because of the role of this diet in the evolution of eusociality in Blattodea (i.e. cockroaches and termites). We used two sets of morphological data while taking into account the phylogenetic relationships of 62 species of cockroaches, sampled from nine families and covering three fossorial (hollow trunk, sand, dead wood) and two non‐fossorial microhabitats (litter and under bark). The first set of data corresponded to linear measurements for 13 morphological traits, while the second set comprised 3D models of pronotums obtained by photogrammetry and microtomography and analysed by geometric morphometrics. To account for shared ancestry between species, phylogenetic comparative analyses were then carried out, including predictive analyses for six species whose microhabitat are unknown. We identified morphological differences associated with different burrowing lifestyles while highlighting the importance of considering shared ancestry. Among the most discriminating morphological traits are body length and anterior tibial spine length, which distinguish species burrowing in deadwood from those digging in sand. 3D analyses of the pronotum also revealed interesting differences related to the microhabitat. Despite the ability to characterize ecomorphs from both sets of data, predictive analyses, which would be particularly valuable for all the living and fossil species whose microhabitats is unknown—that is, the vast majority of cockroach species‐need further refinement. Read the free Plain Language Summary for this article on the Journal blog.