Morfologia comparada e evolução do pigídio em Apionini (Coleoptera, Brentidae, Apioninae)

Abstract

Apioninae (Coleoptera: Brentidae) is a monophyletic group, with approximately 2,200 species of phytophages insects, distributed over the continents. Comparative morphological and phylogenetic studies are preliminary for the subfamily, reflecting on a classification system considered controversial and lacking in evolutionary understanding, such as the inconsistent division of the Apioninae into the supertribes Aspidapiitae and Apionitae based on two general morphological patterns of the pygidium: aspidapionine type and apionine type, respectively, which makes it difficult to understand of the phylogenetic relationships and delimitation of Apionini taxa, a group that comprises 90% of the diversity of the Apioninae. The detailed and comparative understanding of pygidium morphology is fundamental for taxonomy, stabilization of the classification system and development of studies about the relationships between the taxa of Apioninae and, therefore, needs to be revised. Taking this into account, a phylogenetic analysis was carried out based on molecular and morphological data of 170 species of Brentidae, 28 species of the outgroup, belonging to Nanophyinae, Brentinae, Cyladinae, Eurhynchinae, and Apioninae [Antliarhinitae, Rhadinocybitae (Rhadinocybini) and Rhinorhynchidiini], and 142 ingroup species, representing 13 of the 14 valid Apionini subtribes: Aplemonina, Apionina, Trichapiina, Piezotrachelina, Exapiina, Ixapiina, Malvapiina, Aspidapiina, Kalcapiina, Ceratapiina, Catapiina, Metapiina, and Oxystomatina. The phylogenetic reconstruction and relationships obtained were used to infer the evolution of 25 morphological characters of the pygidium, collected from the literature and/or from the examination of specimens of museums. The findings suggest, in an unprecedented way, a hypothesis about the possible plesiomorphic condition of the pygidium for the hypothetical common ancestor of the Apionini, with the following character states: 1) partially exposed pygidium between the elytral apices and the margin of the 5th ventrite, 2) transverse sulcus present, 3) apical flange present, 4) distinct, punctate, pubescent apical rim, and 5) tongue-like process absent. Furthermore, the reinterpretation of the pygidium characters and the results presented suggest the abandonment of the use of pygidium types in the delimitation of taxa and in the proposition of relationships among the Apionini, as they are inconsistent in the delimitation of basal and apical groups of Apioninae, and reinforces the need for morphological studies with more detailed descriptions of the pygidium morphology, fundamental for the delimitation of taxa and for the elucidation about the relationships between groups of Apioninae.