Revalidation and redescription of three distinct species synonymized as Plagiometriona sahlbergi (Coleoptera: Chrysomelidae: Cassidinae)

Abstract: Plagiometriona sahlbergi (Boheman, 1855), P. multisignata (Boheman, 1855) and P. scenica (Boheman, 1855) were described over a century and half ago as separate species based on dry museum specimens. The latter two were later synonymized with P. sahlbergi. While observations in nature find both P. sahlbergi and P. multisignata co-occurring on the same host plant, subtle morphological differences suggested they may be distinct species. We tested the validity of the original species separation using additional morphological characters and available molecular sequence data. The new evidence supports Boheman’s original separation of species. Accordingly we remove P. multisignata stat. restit. and P. scenica stat. restit. from synonymy with P. sahlbergi and restore their species status. Mitochondrial gene sequence data suggest that P. sahlbergi and P. multisignata bear a closer relationship to other sympatric Plagiometriona species than they do to one another, raising the possibility that these two species have convergent morphologies due to their shared food plant. Biological and ecological notes are also given for these two sympatric species.

Key words: Coleoptera, Chrysomelidae, Cassidinae, Plagiometriona, synonymy, phylogeny, cytochrome oxidase I, morphology, Atlantic Forest, Brazil, Neotropical Region