The puzzling mitochondrial phylogeography of the black soldier fly (Hermetia illucens), the commercially most important insect protein species

Gunilla Ståhls (Corresponding Author), Rudolf Meier, Christoph Sandrock, Martin Hauser, Ljiljana Šašić Zorić, Elina Laiho, Andrea Aracil, Jovana Doderović, Rozane Badenhorst, Phira Unadirekkul, Nur Arina Binte Mohd Adom, Leo Wein, Cameron Richards, Jeffery K. Tomberlin, Santos Rojo, Sanja Veselić, Tuure Parviainen

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    Abstract

    Background: The black soldier fly (Diptera: Stratiomyidae, Hermetia illucens) is renowned for its bioconversion ability of organic matter, and is the worldwide most widely used source of insect protein. Despite varying extensively in morphology, it is widely assumed that all black soldier flies belong to the same species, Hermetia illucens. We here screened about 600 field-collected and cultured flies from 39 countries and six biogeographic regions to test this assumption based on data for three genes (mitochondrial COI, nuclear ITS2 & 28S rDNA) and in order to gain insights into the phylogeography of the species. Results: Our study reveals a surprisingly high level of intraspecific genetic diversity for the mitochondrial barcoding gene COI (divergences up to 4.9%). This level of variability is often associated with the presence of multiple species, but tested nuclear markers (ITS2 and 28S rDNA) were invariant and fly strain hybridization experiments under laboratory conditions revealed reproductive compatibility. COI haplotype diversity is not only very high in all biogeographic regions (56 distinct haplotypes in total), but also in breeding facilities and research centers from six continents (10 haplotypes: divergences up to 4.3%). The high genetic diversity in fly-breeding facilities is mostly likely due to many independent acquisitions of cultures via sharing and/or establishing new colonies from field-collected flies. However, explaining some of the observed diversity in several biogeographic regions is difficult given that the origin of the species is considered to be New World (32 distinct haplotypes) and one would expect severely reduced genetic diversity in the putatively non-native populations in the remaining biogeographic regions. However, distinct, private haplotypes are known from the Australasian (N = 1), Oriental (N = 4), and the Eastern Palearctic (N = 4) populations. We reviewed museum specimen records and conclude that the evidence for introductions is strong for the Western Palearctic and Afrotropical regions which lack distinct, private haplotypes. Conclusions: Based on the results of this paper, we urge the black soldier fly community to apply molecular characterization (genotyping) of the fly strains used in artificial fly-breeding and share these data in research publications as well as when sharing cultures. In addition, fast-evolving nuclear markers should be used to reconstruct the recent invasion history of the species.

    Original languageEnglish
    Article number60
    Pages (from-to)60
    JournalBMC Evolutionary Biology
    Volume20
    Issue number1
    DOIs
    Publication statusPublished - 24 May 2020
    MoE publication typeA1 Journal article-refereed

    Keywords

    • Black soldier fly
    • Hermetia illucens
    • mtDNA COI haplotypes
    • Nuclear rDNA

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