Close relatives of Mediterranean endemorelict hoverflies (Diptera, Syrphidae) in South Africa : Morphological and molecular evidence in the Merodon melanocerus subgroup

An ongoing study of the genus Merodon Meigen, 1803 in the Republic of South Africa (RSA) has revealed the existence of new species related to M. melanocerus Bezzi, 1915. The M. melanocerus subgroup belongs to the Afrotropical lineage of the M. desuturinus group. Revision of all available material from museums and detailed analyses of newly -collected specimens from our own expeditions to RSA resulted in delimitation of five species: M. capensis Hurkmans sp. n., M. commutabilis Radenkovic et Vujic sp. n., M. drakonis Vujic et Radenkovic sp. n., M. flavocerus Hurkmans sp. n. and M. melanocerus. In addition to classical morphological characters, sequences of the mitochondrial COI gene are provided for four related taxa. Results of molecular phylogenetic analyses supports monophyly of the M. desuturinus group and confirmed delimitation between species. Links between Palaearctic and Afrotropical faunas of this group, as well as possible evolutionary paths, are discussed. Based on phylogenetic analyses, four lineages (putative subgenera) have been recognized within the genus Merodon; besides the three previously established ones, albifrons+desuturinus, aureus (sensu lato) and avidus-nigritarsis, one new lineage named natans is distinguished.Peer reviewe

Molecular and Morphological Inference of Three Cryptic Species within the Merodon aureus Species Group (Diptera:Syrphidae)

The Merodon aureus species group (Diptera: Syrphidae: Eristalinae) comprises a number of different sub-groups and species complexes. In this study we focus on resolving the taxonomic status of the entity previously identified as M. cinereus B, here identified as M. atratus species complex. We used an integrative approach based on morphological descriptions, combined with supporting characters that were obtained from molecular analyses of the mitochondrial cytochrome c oxidase I gene as well as from geometric morphometry of wing and surstylus shapes and environmental niche comparisons. All applied data and methods distinguished and supported three morphologically cryptic species: M. atratus stat. nov., M. virgatus sp. nov. and M. balkanicus sp. nov., which constitute the M. atratus species complex. We present an identification key for the sub-groups and species complexes of the M. aureus species group occurring in Europe, describe the taxa and discuss the utility of the applied methods for species delimitation. The estimated divergence times for the species splits of these taxa coincide with the Pleistocene Gunz-Mindel interglaciation and the Great interglaciation (between the Ris and Mindel glacial periods).Peer reviewe

Defining species boundaries in the Merodon avidus complex (Diptera, Syrphidae) using integrative taxonomy, with the description of a new species

Several recent studies have detected and described complexes of cryptic and sibling species in the genus Merodon (Diptera, Syrphidae). One representative of these complexes is the Merodon avidus complex that contains four sibling species, which have proven difficult to distinguish using traditional morphological characters. In the present study, we use two geometric morphometric approaches, as well as molecular characters of the 5' -end of the mtDNA COI gene, to delimit sibling taxa. Analyses based on these data were used to strengthen species boundaries within the complex, and to validate the status of a previously-recognized cryptic taxon from Lesvos Island (Greece), here described as Merodon megavidus Vujic & Radenkovic sp. nov. Geometric morphometric results of both wing and surstylus shape confirm the present classification for three sibling species-M. avidus (Rossi, 1790), M. moenium Wiedemann in Meigen, 1822 and M. ibericus Vujic, 2015-and, importantly, clearly discriminate the newly-described taxon Merodon megavidus sp. nov. In addition to our geometric morphometric results, supporting characters were obtained from molecular analyses of mtDNA COI sequences, which clearly differentiated M. megavidus sp. nov. from the other members of the M. avidus complex. Molecular analyses revealed that the earliest divergence of M. ibericus occurred around 800 ky BP, while the most recent separation happened between M. avidus and M. moenium around 87 ky BP.Peer reviewe

The Merodon planifacies subgroup (Diptera, Syrphidae) : Congruence of molecular and morphometric evidences reveal new taxa in Drakensberg mountains valleys (Republic of South Africa)

Hoverflies (Syrphidae) represent an insect group of great importance in ecosystems and indicators of ecosystem change. The genus Merodon Meigen, 1803 (tribe Merodontini) is one of the most species-rich hoverfly genera, distributed across the Palaearctic and Afrotropical regions. The genus Merodon Meigen, 1803 is less diverse in the Afrotropical Region than in the Palaearctic (11 versus 160 known species). An ongoing study of the genus Merodon in Africa has revealed the existence of two new species into the taxon previously known as Merodon planifacies Bezzi, 1915. The M. planifacies subgroup belongs to the Afrotropical lineage of the Merodon desuturinus group. Morphological analysis of male genitalia has classified the available specimens of the M. planifacies taxon into two sets: the first one corresponds to M. planifacies with folded theca, while the other with smooth theca, later named Merodon capi complex was found exclusively at the Drakensberg mountains in the Republic of South Africa, specifically in the Cathedral Peak National Park and the Royal Natal National Park. Further, molecular and morphometric evidences revealed two cryptic taxa within this complex: M. capi sp. nov. Vujic et Radenkovic and Merodon roni sp. nov. Radenkovic et Vujic. (c) 2020 Elsevier GmbH. All rights reserved.Peer reviewe

An integrative approach in the assessment of species delimitation and structure of the Merodon nanus species group (Diptera: Syrphidae)

The Merodon nanus group (Diptera, Syrphidae) is a small group of closely related species with high morphological similarity. Until now, based on morphological characters, this group consisted of five species: M. nanus Sack, 1931; M. telmateia Hurkmans, 1987; M. kopensis Vuji et Hayat, 2015; M. neonanus Vuji et Taylor, 2015; and M. rasicus Vuji et Radenkovi, 2015. Here, using an integrative approach based on molecular characters (sequences of the D2-3 region of the nuclear 28S rRNA gene and the mitochondrial COI gene) and data obtained from geometric morphometry of wing shape, we distinguish all five previously morphologically defined species of the group. Additionally, we identify one species as being new to science, M. vladimiri Vuji et Koi Tubi sp. n. We emphasize the separation of this newly described species according to the sequences obtained from the slowly evolving 28S rRNA gene, which demonstrated four to five mutation positions between this species and morphologically the most similar M. neonanus species. Also, our results show a clear division of M. telmateia into at least three population groups that we designate as the subspecies: M. telmateia mediterraneus Aanski et Koi Tubi subsp. n. and M. telmateia samosensis Aanski et Koi Tubi subsp. n. exhibiting western distributions (western Anatolia and the Greek island of Samos, respectively) and the nominative subspecies M. telmateia telmateia with an eastern Anatolian distribution.Peer reviewe

Genetic architecture of disease resistance and tolerance in Douglas-fir trees.

Understanding the genetic basis of how plants defend against pathogens is important to monitor and maintain resilient tree populations. Swiss needle cast (SNC) and Rhabdocline needle cast (RNC) epidemics are responsible for major damage of forest ecosystems in North America. Here we investigate the genetic architecture of tolerance and resistance to needle cast diseases in Douglas-fir (Pseudotsuga menziesii) caused by two fungal pathogens: SNC caused by Nothophaeocryptopus gaeumannii, and RNC caused by Rhabdocline pseudotsugae. We performed case-control genome-wide association analyses and found disease resistance and tolerance in Douglas-fir to be polygenic and under strong selection. We show that stomatal regulation as well as ethylene and jasmonic acid pathways are important for resisting SNC infection, and secondary metabolite pathways play a role in tolerating SNC once the plant is infected. We identify a major transcriptional regulator of plant defense, ERF1, as the top candidate for RNC resistance. Our findings shed light on the highly polygenic architectures underlying fungal disease resistance and tolerance and have important implications for forestry and conservation as the climate changes