Taxonomic revision of Chilean <i>Liogenys</i> (Coleoptera: Melolonthidae) and molecular assessment of a species complex

Abstract Liogenys is a neotropical genus widely distributed in South America and characterized by rhizophagous feeding habits. Taxonomy survey of Liogenys from Chile revealed a species complex consisting of L. palpalis, L. obesula and an undescribed morphotype. Morphological data alone are not sufficient to distinguish between them. The three-species hypothesis was tested using phylogenetic and preliminary phylogeographic analyses, as well as unilocus delimitation methods using mitochondrial (COI) and nuclear (ITS2) markers. The tree-based PTP method based on ITS2 considers both L. obesula and the undescribed morphotype to be variants of L. palpalis, a single, polymorphic species. Haplotypes from 12 localities along central Chile revealed four genetically structured populations, with statistical variance (54.34%) only within them. Isolated populations occur in Southern Santiagan Region and coastal desert. There are eight species of Liogenys in Chile. Diagnoses are provided for five species. Liogenys elguetai sp. nov. is described. Five synonyms are proposed for three species. Liogenys pubisternis, a new synonym of L. palpalis, is transferred from Diplotaxis. Lectotypes are provided for four names (L. castaneus, L. grandis, L. pubisternis, and Melolontha palpalis). Liogenys boliviensis is recorded for the first time from Chile and Peru, extending the distribution of Liogenys to northernmost Chile.