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A new taxonomic status for Darwin’s “predicted” pollinator: Xanthopan praedicta stat. nov.
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Edité par CCSD ; Imprimitur -
International audience. The taxonomic status of the famous Malagasy hawkmoth known as “Darwin’s Moth” or “Wallace’s Sphinx Moth” is revised after a thorough integrative study combining comparative analyses of morphological characters (“habitus”, genitalia, proboscis length, etc.) and molecular data (DNA barcoding essentially). While the existence of this long-tongued, large moth in Madagascar had been predicted by Charles DARWIN (in 1862), who considered such insect as the probable pollinator of the endemic, long-spurred orchid Angraecum sesquipedale Thouars, 1822, the discovery and description of this moth occurred about two decades after Darwin’s death. It was named praedicta by Lord Walter ROTHSCHILD and Karl JORDAN, in 1903, in reference to Alfred Russel WALLACE’s prediction (in 1867, about a hawkmoth pollinator) and has always been regarded, until now, as a subspecies of Xanthopan morganii (Walker, 1856), a species known to occur in the continental afrotropical region (remarkably, the hawkmoth species envisioned by WALLACE to be a possible close relative of the hypothetical pollinator of A. sesquipedale). We propose to raise the taxon praedicta to species rank on account of several clear-cut morphological differences and a high genetic divergence (ca. 7.8 % for the DNA barcode) with the African and Comorian taxon X. morganii. Delimiting species with such criteria is indeed presently considered an appropriate method in the case of allopatric taxa (within the framework of the Biological Species Concept). Our work reveals that the proboscides of Xanthopan morganii and Xanthopan praedicta differ significantly in average length (with a difference of ca. 6.6 cm), suggesting a probable adaptation to different sets of visited flower species.
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