Key long-proboscid fly pollinator overlooked: morphological and molecular analyses reveal a new Prosoeca (Nemestrinidae) species

Abstract

Abstract Long-proboscid nemestrinid flies are keystone pollinators of dozens of Southern African plants and, consequently, their taxonomic status might have important consequences for insect and plant conservation. We focus on Prosoeca peringueyi, considered to be a single, morphologically variable species, upon which a guild of ~28 plants in the winter rainfall region depends for pollination. We quantified morphological variation and established whether it was associated with genetic variation within and among sites. Phylogenetic analyses of the mitochondrial COI gene revealed two well-supported clades. One clade contains long-proboscid individuals that conform morphologically to the holotype of P. peringueyi. The sister clade contains individuals that frequently occur sympatrically with P. peringueyi and have shorter proboscides, with additional diagnostic characters that set it apart from P. peringueyi. A haplotype analysis based on nuclear ribosomal 28S DNA sequences of a subset of individuals corroborated these results. Based on our results, we propose the recognition of two species: P. peringueyi and Prosoeca torquata sp. nov., which is described here. Future research is required to quantify the interaction networks of these two fly species and the plant guilds with which they interact, to facilitate conservation in the global biodiversity hotspot where they occur.