A phylogeny of the treehopper subfamily Heteronotinae (Hemiptera: Auchenorrhyncha: Membracidae) reveals lineage-specific trends in extreme morphological plasticity

Treehoppers in the family Membracidae are entomologically famous for the extreme morphological diversity of their pronotum, which often consists of brightly colored and/or curiously shaped structures that have long puzzled researchers and amateurs alike. With regard to pronotal morphology, the Neotropical treehopper subfamily Heteronotinae is amongst the most diverse, displaying remarkably dissimilar pronota among its 9 currently recognized genera. For example, the genus Heteronotus is conspicuous with complex arrangements of pronotal nodes and spines that mimic ants and wasps; species of Anchistrotus have highly inflated pronota with detachable bulbs; and Rhexia species have scoop-shaped pronotal shields that are thought to mimic beetles. Despite this amazing morphological diversity and the fact that species of Heteronotinae display a range of evolutionarily interesting behaviors (aggregating behavior, maternal care, communication via substrate-borne signals, and ant-tending), the phylogeny and evolution of the subfamily remains virtually unexplored. The present study investigates the phylogenetic relationships within Heteronotinae based on a combination of molecular characters from six nuclear and mitochondrial markers (28S, H2A, H3, Wg, COI, ND1) and coded morphological characters. The objectives of this research are to: 1) reconstruct the phylogeny of Heteronotinae with emphasis on inter-generic relationships; 2) revise the generic-level classification of Heteronotinae in a phylogenetic context such that the classification supports the substantial species diversity in need of formal description; and 3) investigate the evolution of morphological plasticity in traits (such as the pronotum and male genitalia) within seemingly autapomorphic heteronotine lineages.