Beyond the obvious: diversity and evolution of cuticular microsculpture in jumping plant lice of the subfamilies Aphalarinae and Rhinocolinae (Hemiptera, Psylloidea, Aphalaridae)

Cuticular microsculpture is an important morphological feature in insects, but it has not been systematically investigated in psyllids (Hemiptera: Psylloidea). Here, we examine the microsculpture of the vertex and thoracic dorsum in two subfamilies of Aphalaridae, focusing mainly on European taxa and using scanning electron microscopy to evaluate its taxonomic and phylogenetic significance. In Aphalarinae, imbricate microsculpture was observed in Aphalara , Eumetoecus and Rhodochlanis ; rugose microsculpture in most species of Colposcenia ; and several microsculptural types in Craspedolepta , including imbricate, smooth–imbricate, areolate–rugose, and alveolate patterns. A unique tuberculate microsculpture was found in Rhinocola aceris (Linnaeus, 1758), whereas other Rhinocolinae exhibited an imbricate pattern. Ancestral state reconstruction indicates that imbricate microsculpture represents the plesiomorphic condition in Aphalaridae and remains expressed to varying degrees in most extant representatives of the family. Multiple transitions among sculptural types within Craspedolepta and partly also Colposcenia indicate that microsculpture can evolve relatively rapidly, although the distribution of character states across the phylogeny shows that it still retains phylogenetic signal at shallow to intermediate taxonomic levels, despite a moderate level of homoplasy. Overall, these results demonstrate that head and dorsal thoracic microsculpture constitute diagnostic and phylogenetically informative characters that can be more widely applied in taxonomy, systematics and evolutionary research on psyllids.