Evolution and recent speciation in two disparate endemic South African insect genera: Macroderes (Coleoptera: Scarabaeidae) and Nemopterella (Neuroptera: Nemopteridae)

Abstract

Phylogenetic, taxonomic and biogeographic analyses were conducted to investigate the role of the paleoclimatic and geological oscillations on the diversification and evolutionary history of two disparate southern African insect genera: the dung beetle genus Macroderes Westwood, 1842 and the lacewing genus Afroptera Abdalla & Mansell, 2019. The taxonomic revision of Macroderes resulted in the description of seven new species: M. cederbergensis Abdalla & Deschodt, 2018, M. tortuosus Abdalla & Scholtz, 2018, M. gifboomi Abdalla & Scholtz, 2018, M. leipoldti Abdalla & Deschodt, 2018, M. oreatus Abdalla & Deschodt, 2018, M. porselinus Abdalla, 2018 and M. soleiana Abdalla & Deschodt, 2018. One species, Macroderes nitidus Harold, 1877 is redescribed and its lectotype designated. The diagnostic characters as well as an updated geographic distribution of each species are considered. An identification key to the species in the genus, photographs of habitus, internal sac sclerite, pronotum, pronotal punctures and elytra are also provided. The phylogenetic analyses, based on concatenated molecular and combined concatenated molecular and morphological datasets, suggest Macroderes as a monophyletic group within the Scarabaeinae with strong statistical support. Molecular dating estimation suggests that the genus emerged approximately 38.9 Mya. Rapid recent speciation occurred during the late Miocene and throughout the Plio-Pleistocene eras (5.0-0.1 Mya), which is ascribed to the effects of the paleoclimatic and geological oscillations during the late Mio-Pliocene and the recurrent warming and cooling of the Pleistocene. Taxonomic revisions of the genera Nemopterella Banks, 1910 and Nemia Navás, 1915 resulted in the split of Nemopterella into three: Nemopterella sensu stricto with type species Nemopteryx africana Leach, 1815 (= Nemopterella africana), Afroptera Abdalla & Mansell, 2019 with type species Nemopterella munroi Tjeder, 1967, and the monotypic genus Siccanda Abdalla & Mansell, 2019, with type species Nemopterella arenaria Tjeder, 1967. Eight new species are described in the genus Afroptera these are: A. acuta Abdalla & Mansell, 2019, A. alba Mansell & Abdalla, 2019, A. brinkmani Abdalla & Mansell, 2019, A. balli Abdalla & Mansell, 2019, A. cylindrata Abdalla & Mansell, 2019, A. folia Abdalla & Mansell, 2019, A. koranna Mansell & Abdalla, 2019 and A. maraisi Abdalla & Mansell, 2019. In addition, two new species are added to Nemopterella: N. kabas Mansell & Abdalla, 2019 and N. cedrus Mansell & Abdalla, 2019. Nemia remained unaffected by these changes. The phylogenetic analyses based on concatenated molecular and combined concatenated molecular and morphological datasets Afroptera resulted in well-supported phylogeny and two major clades were identified. The Divergence time estimates suggest that Afroptera originated in the early Eocene (53.9 Mya) but commenced diversification in the late Eocene 36.5 Mya. Most descendant species underwent rapid recent speciation during the late Mio-Pliocene and through the Pleistocene 4.6-0.2 Mya. Biogeographic analyses of Macroderes and Afroptera indicate that the genera have different spatiotemporal origins. The most common ancestor of Macroderes originated in the Cape Floristic Region or the Namaqualand-Namib Domain and the Cape Floristic Region (CFR) during the late Eocene 38.9 Mya and evolved in the Namaqualand-Namib Domain and CFR in the late mid-Miocene 14.5 Mya. By contrast, the most common ancestor of Afroptera is shown to have originated earlier, during the Early Eocene (53.9 Mya) in the Namaqualand-Namib Domain, the Cape Floristic Region and Namib Desert Eco-region and evolved in the Namaqualand-Namib Domain and Namib Desert Eco-region during late Eocene 36.5 Mya. Dispersal was found to be the most prominent ecological mechanism that led to the present-day distribution of extant species. The late Mio-Pliocene witnessed synchronised dispersal and vicariant events for both genera resulting in synchronised lineage splitting in many of their populations; indicating that the genera experienced the same paleoclimatic and geological processes driving speciation. The extant species of both genera appear to have evolved during the Pleistocene.