First conservation assessment of selected long-proboscid flies (Moegistorhynchus and Prosoeca, Diptera: Nemestrinidae) endemic to South Africa’s Cape region

Abstract

Long-proboscid flies of the genera Moegistorhynchus and Prosoeca (Nemestrinidae) are charismatic nectar-feeding insects with several species considered to be keystone pollinators, yet their conservation status is unknown. Recent taxonomic work has improved our understanding of some species identities and distributions, therefore providing a basis for conservation assessments. Building on this updated taxonomy, we conducted baseline IUCN Red List assessments for eight endemic species to evaluate their extinction risk. We estimated range-size metrics following IUCN guidelines and incorporated national spatial overlays to assess habitat loss, ecosystem threat status, and protected area coverage. We found that two species are classified as Endangered, one as Near Threatened, three as Data Deficient and two as Least Concern. All species assessed have experienced high habitat loss (28–57%) as a result of agriculture and urban expansion, particularly along coastal areas, and 8–31% of the remaining habitat falls within threatened ecosystems. Less than 11% of the ranges of the Endangered and Near Threatened species overlap with protected areas. Data Deficient species are known from fewer than three localities, underscoring the need for systematic surveys and intensive sampling of these poorly known taxa. Information on distributions, population sizes, host plants, and larval biology remains extremely limited for all taxa and is urgently needed. As the first Red List assessment for flies in South Africa, and for a specialist fly pollinator, this study identifies threatened species, highlights data-deficient taxa, and provides important baseline information for future research and conservation efforts on this hyper-diverse insect group.