Phylogeny of Ochlerini (Hemiptera: Pentatomidae: Discocephalinae) and the evolution of the apical tarsomere in hind legs

Tarsal morphology in insects is highly variable and has attracted the attention of scientists in different fields, but the dorsal tarsal morphology is virtually unexplored. We evaluated the morphological diversity of the dorsal surface of the apical tarsomere in Ochlerini under a phylogenetic framework, ascertaining whether the presence of a depression is influential in the phylogeny and whether the features in the apical tarsomere of the hind legs evolved in the same way in females and in males. The presence and extent of a depression, the presence of setae and the presence and type of cuticular microsculpture were evaluated through reconstruction of ancestral character states and correlation analysis. Depressed tarsomeres were found in a few species outside Ochlerini, and dorsal setae were not observed in ochlerine females. The setae were lost first in females; their absence was correlated with the presence of both basal and discal depression. The dorsal tarsomere surface in females more probably evolved from convex at the base to flat in the Neoadoxoplatys clade and concave in the Pseudadoxoplatys clade, whereas the discal concavity showed a history of several independent acquisitions or losses. The more structured pattern for this character in females might be speculated to result from female-specific evolutionary trends, such as oviposition behaviour.