Higher-level phylogenetics and character evolution of the millipede assassin bugs (Heteroptera: Reduviidae: Ectrichodiinae)

Millipede assassin bugs, or Ectrichodiinae, comprise the fifth largest subfamily (>600 species, ~120 genera) of Reduviidae (Heteroptera). Ectrichodiinae specialize on chemically defended millipedes (Diplopoda), a group few arthropods exploit. They further stand out among other reduviids in the large number of brightly or metallically colored, sexually dimorphic, and wing polymorphic species. These phenomena make Ectrichodiinae an attractive group for ecological, behavioral, and evolutionary research, which is currently hindered by a lack of phylogenetic hypotheses. The few morphological and molecular phylogenies of Reduviidae that incorporate millipede assassin bugs support a clade formed by Ectrichodiinae and Tribelocephalinae, a small subfamily of ~130 dull-colored species (16 genera) with few known cases of extreme sexual dimorphism. However, the monophyly of neither subfamily is firmly established. To investigate Ectrichodiinae monophyly and generic relationships, the first comprehensive cladistic analysis of Ectrichodiinae is performed for 72 ectrichodiine and 8 tribelocephaline genera using morphological and, for a subset of taxa, molecular data (COI, 28S D2, 28S D3-D5, 16S, 18S). Ancestral state reconstruction is performed to investigate evolution of coloration and extreme sexual dimorphism. This analysis will serve as a foundation for a suprageneric classification based on diagnostic characters and relationships among genera.