A tale of two ends: Evolution of head and male genitalic morphology of Nannocoris Reuter (Hemiptera: Schizopteridae)

Nannocoris Reuter, a diverse genus of minute litter bugs within the family Schizopteridae (Hemiptera: Dipsocoromorpha), is currently known from 12 described species from the New World, with greatest diversity in the Neotropics. Assessing the diversity, let alone natural history, of these obscure insects is difficult as they are tiny (1mm) and rarely collected. Our ongoing survey of Nannocoris has revealed at least four times as many undescribed species that exhibit drastic species-specific differences with respect to head shape and male genitalic morphology. Compared to other genera of Schizopteridae, Nannocoris displays dramatic variation in length of the male intromittent organ, the so-called vesica, ranging from one quarter of the total body length to about 10 times the body length in different species – a trait that has potentially driven the diversification in this genus. Our molecular hypothesis is the first phylogenetic analysis of the group, testing the monophyly of the genus and investigating species level relationships across Nannocoris. Using ancestral state reconstruction, this phylogeny is used to investigate the origin of the pointed, elongate head that is found in some but not all species of Nannocoris and to trace the evolution of the exaggerated male vesica.