Phylogeny of the wasp subfamily Metopiinae and patterns of speciation in the Exochus albiceps species-group

Abstract

Metopiinae is a moderately large subfamily with over 850 described species distributed in 28 genera. The validity of Metopiinae had been doubted as they were suggested to be a derived member of the Ctenopelmatinae; and four genera—Apolophus, Bremiella, Ischyrocnemus, and Lapton—were only tentatively placed within the subfamily. Thus, there have been some doubts regarding the monophyly of the subfamily as currently circumscribed, whether the subfamily renders others paraphyletic, what genera should be contained within Metopiinae, and how these genera are interrelated. The results presented here represent only a first step toward revising the systematics of metopiine wasps and creating a phylogenetically sound classification. The morphology-based phylogeny based on 101 terminal taxa (90 for the ingroup plus 11 outgroups) and 176 morphological characters, recovered Metopiinae as monophyletic, and sister to a clade formed by Tryphoninae, Mesochorinae, and Ctenopelmatinae. With respect to the four genera tentatively placed in Metopiinae, only Scolomus clustered well within the subfamily, while Bremiella, Ischyrocnemis, and Lapton were found as sister to the remaining metopiines, with their definitive placement remaining far from being resolved. Four main clades were recovered within the subfamily. The monophyly of most genera was recovered and with good support, and additional synapomorphies are proposed for several genera. However, in all the analyses Stethoncus was nested within Hypsicera; and the genus Forrestopius was not recovered as monophyletic, as Forrestopius larryi clustered within Leurus. Additionally, five new genera were found: Finisterra gen. nov., Huetzin gen. nov., Jirajara gen. nov., Wira gen. nov., and Yanesha gen. nov. The new genera inhabit high elevation regions of the Neotropical Region, areas that are poorly explored. Base on this phylogenetic analysis of the subfamily, the monophyly of Exochus albiceps species-group was demonstrated. The monophyly of the albiceps species-group was well supported by morphological characters but poorly supported by the gene 28S, the combined molecular (28S, ND1, and Wg), and the combined molecular and morphological analyses. In addition to E. albiceps and E. tegularis, three species are newly assigned—E. ablatus Gauld & Sithole, 2002, E. izbus Gauld & Sithole, 2002, and E. jacintus Gauld & Sithole, 2002—and another six species newly described from the Neotropical region. In order to investigate the spatial variation and niche requirements of the albiceps species-group, a climate-based modelling of species’ niches was employed to estimate the level of niche overlap between species within the E. albiceps species-group, seeking to elucidate the relationship between elevational range and niche breadth. Segregation in the environmental space was found between species inhabiting the lowlands and the ones inhabiting montane regions. There is niche partitioning among the species that inhabit in montane regions while the lowland species occupied similar ecological space. The species show to have a narrow physiological thermal tolerance and are specialized for life at specific elevations.