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| Leoheo domatiophorus Chaowasku, D.T. Ngo & H.T. Le
in Chaowasku, Damthongdee, Jongsook, et al., 2018.
Lèo Heo || DOI: 10.15553/c2018v732a11
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Recent botanical expeditions in central Vietnam yielded an unknown species of Annonaceae that could not be confidently identified to subfamily, tribe, and genus. Preliminary BLAST® searches based on plastid data have suggested that this taxon is genetically closely-related to the following tribes of subfamily Malmeoideae: Malmeeae, Fenerivieae, Maasieae, Phoenicantheae, Dendrokingstonieae, Monocarpieae, and Miliuseae. Using representatives of Piptostigmateae, another tribe of Malmeoideae, as outgroups and including representatives of all other tribes of Malmeoideae, molecular phylogenetic analyses of seven combined plastid markers (rbcL, matK, ndhF, ycf1 exons; trnL intron; trnL-trnF, psbA-trnH intergenic spacers) inferred the enigmatic Vietnamese taxon as belonging to the monotypic tribe Monocarpieae. Detailed morphological comparisons between this taxon and its sister group, Monocarpia Miq., warranted the recognition of a second genus of Monocarpieae to accommodate our unknown taxon: Leoheo Chaowasku with a single species, Leoheo domatiophorus Chaowasku, D.T. Ngo & H.T. Le. The morphology of the new genus agrees well with the diagnostic traits of Monocarpieae, e.g., a percurrent tertiary venation of the leaves, a highly reduced number of carpels per flower, enlarged and lobed stigmas, multiple ovules/seeds per ovary/monocarp, considerably large monocarps with a hardened pericarp when dry, and spiniform ruminations of the endosperm. However, the new genus does not exhibit two characteristic features of Monocarpia: terminal inflorescences and generally distinct intramarginal leaf veins. In addition, the new genus possesses three autapomorphic characters: hairy domatia on the lower leaf surface, longitudinal ridges on the monocarp surface, and subsessile monocarps with a stout stipe. The tribe Monocarpieae is consequently enlarged to include the genus Leoheo. The enlarged Monocarpieae, along with the recently established monotypic tribe Phoenicantheae and two other related tribes, Dendrokingstonieae and Miliuseae, are discussed.
Keywords: ANNONACEAE, Monocarpieae, Leoheo, Vietnam, Molecular phylogeny, New genus, New species, Taxonomy
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| Fig. 5. – Reproductive organs of Leoheo domatiophorus Chaowasku, D.T. Ngo & H.T. Le: A. Flower with petals and stamens removed; B. Flower with petals, stamens, and carpels removed, back view, showing outer side of sepals; C. Same as (B), but on another side, showing a volcano-shaped torus and inner side of sepals; D. Inner side of an outer petal; E. Outer side of an outer petal; F. Inner side of an inner petal; G. Outer side of an inner petal; H. Stamen, abaxial side; I. Stamen, adaxial side; J. Carpels, showing enlarged and irregularly lobed stigmas; K. Fruit, showing longitudinal ridges on monocarp surface; L. Seed, lateral view, showing a raphe; M. Seed, lateral view, showing a pitted and slightly rugose surface; N. Cross section of a seed, showing spiniform endosperm ruminations.
[A–J: HUAF collectors 2009-03-19-ND, CMUB; K: Chaowasku 131, CMUB; L–N: Chaowasku 165, CMUB]
[Drawing: A. Damthongdee]
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| Fig. 6. – Leoheo domatiophorus Chaowasku, D.T. Ngo & H.T. Le, showing habit with inflorescences and flowers. [HUAF collectors 2009-03-19-ND,CMUB] [Drawing: A. Damthongdee] |
Taxonomy
Leoheo Chaowasku, gen. nov.
Typus: Leoheo domatiophorus Chaowasku, D.T. Ngo & H.T. Le.
Etymology. – The generic epithet Leoheo is from the local Vietnamese name of “Lèo Heo” for this plant and is designated as a masculine noun of nominative singular in third declension with genitive singular “Leoheonis”.
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| C–H: Leoheo domatiophorus Chaowasku, D.T. Ngo & H.T. Le; C. Leaf without intramarginal veins; D. Fruit, showing monocarps with longitudinal ridges; E. Flowering branches; F. Dissected flower and young fruit; G. Dissected flower, showing detached stamens and stigmas; H. Flower, showing enlarged and irregularly lobed stigmas.
[C–D: Chaowasku 131, CMUB; E–H: HUAF collectors 2009-03-19-ND, CMUB]
[Photos: A: Arbainsyah; B: S. Gardner & P. Sidisunthorn; C–H: D.T. Ngo]
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Leoheo domatiophorus Chaowasku, D.T. Ngo & H.T. Le.
Leoheo domatiophorus Chaowasku, D.T. Ngo & H.T. Le, spec. nova
Holotypus: Vietnam. Prov. Thua Thien-Hue: Nam Đông Distr., ... (CMUB!; iso-: G!, P!).
Leoheo domatiophorus Chaowasku, D.T. Ngo & H.T. Le differs from species of the genus Monocarpia Miq. by the lack of intramarginal leaf veins and by having axillary inflorescences, leaf domatia, longitudinal ridges on the monocarp surface, and subsessile monocarps with a stout stipe.
Etymology. – The specific epithet domatiophorus is a masculine adjective in first and second declensions, referring to “domatia” on the lower leaf surface.
Tanawat Chaowasku, Anissara Damthongdee, Hathaichanok Jongsook, Dung T. Ngo, Hung T. Le, Duc M. Tran and Somran Suddee. 2018. Enlarging the Monotypic Monocarpieae (Annonaceae, Malmeoideae): Recognition of A Second Genus from Vietnam informed by Morphology and Molecular Phylogenetics. Candollea. 73(2); 261–275. DOI: 10.15553/c2018v732a11
