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Trait matching between the Madagascan orchid Angraecum sesquipedale, with a nectar spur of 33 cm, and a hawkmoth with a tongue almost as long has fascinated biologists since Darwin, who saw only flowers but correctly predicted the moth pollinator. This moth, Xanthopan morgani praedicta, was described from museum specimens in 1903 and documented as the pollinator in photographs and film in 1992 and 2004. However, Madagascar harbours c. 30 species of long-spurred orchids and seven species of long-tongued hawkmoths, and mutualisms between moths and 'Angraecum and other deep tubular flowers' (Darwin, 1862: p. 202) probably involve a network of interacting species. We infer the evolutionary time over which Madagascan sphingids and Angraecum have interacted, based on an orchid phylogeny that includes 62 of 144 Angraecum species on Madagascar and a moth phylogeny with all nine Madagascan Sphinginae. Clock models using either rate- or fossil-based calibrations imply that the Madagascan subspecies X. morgani praedicta and the African morgani diverged 7.4 +/- 2.8 Mya, which overlaps the divergence of An. sesquipedale from its sister, Angraecum sororium, namely 7.5 +/- 5.2 Mya;since both have extremely long spurs, long spurs probably existed before that. The phylogenies moreover show that several long-tongued moths and long-spurred orchids probably coevolved on Madagascar since the mid-Miocene, although field data on the moths' levels of polyphagy and pollen transport are lacking.

Ilustraciones de Sylvia Strigari Angraecum sesquipedaleThouars, Histoire Particulière des Plantes Orchidées (Hist. Orchid.), pl. 66 & 67. 1822. TYPE: Madagascar, without specific locality, 1798, L. M. A.-A. du Petit-Thouars s.n.; lectotype, designated by Du Puy et al. (1999), plates 66 and 67 of Hist. Orch. A large, epiphytic, lithophytic or semiterrestrial, monopodial, erect herb to over 60 cm tall. Roots flexuous, glabrous, thick, to 8 mm in diameter, produced from the base of the node subopposite to the leaf on the lower part of the stem. Stem slightly flattened, to 12 mm wide, completely covered by the conduplicate, subancipitous, tightly clasping leaf sheaths, the oldest ones becoming brownpapyraceous. Leaves articulate with the sheaths, coriaceous, dark green, detaching when old, ligulate, irregularly bilobed at apex, 10–30 × 1.4–2.7 cm. Inflorescence produced laterally from the stem and emerging from the axil of one of the upper sheaths, a lateral, 1- (Ang. sesquipedale var. angustifolium) to few-flowered (no more than six), arched to gently pendent, successive or simultaneously flowering raceme 25–30 cm long including the peduncle; peduncle terete, green, 10–12 cm long, with 2–3 triangular, cucullate, hyaline bracts becoming brownish with age, ca. 1 cm long. UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Agroalimentarias::Jardín Botánico Lankester (JBL)

The display of scent is crucial for plants in attracting pollinating insects to flowers and ensuring successful pollination and reproduction. The large number of aldoxime volatile species present in the scent of the Madagascan orchid Angraecum sesquipedale has been suggested to play a primary role in attracting the sphingid moth Xanthopan morgani praedicta. By solid phase micro-extraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS), we monitored the scent release from different flowers of a single orchid, day and night throughout the entire flowering period. In separate experiments, the diurnal release was monitored in 3h intervals and the tissue specific release from the different floral parts was tracked. Numerous novel compounds related to the aldoxime metabolism not previously detected in A. sesquipedale were identified and positioned into a proposed pathway for aldoxime metabolism. From the results, we hypothesize that (E/Z)-phenylacetaldoxime and its derivatives could be important attractants for the pollinating moth X. morgani praedicta. By applying an untargeted Partitioning Around Medoids (PAM) cluster analysis to the metabolite profiles in the scent, the proposed pathways for the formation of aldoximes were substantiated. With this study, we demonstrate the powerful utility of a bioinformatics tool to aid in the elucidation of the routes of formation for volatiles and provide a benchmark and guidelines for future detailed observations of hawkmoth pollination of Angraecum species, and in particular A. sesquipedale, in the wild.