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| Syagrus harenae B.F.Sant’Anna-Santos, in Sant’Anna-Santos, Nunes, Micheli et Francino, 2025. |
Abstract
Background and aims – The Serra do Ambrósio is a mountain with a unique vegetation called carrasco. The carrasco is characterised by sandy soils of high granulometry and is home to rare species. During the current research on the Arecaceae flora of the Diamantina Plateau, a new Syagrus species was discovered, which is described here.
Material and methods – The morphology and anatomy are described based on field collections. The pinnae anatomy was analysed using LM (free-hand cross sections). The new species belongs to the Syagrus glaucescens complex, and an identification key and a distribution map were created.
Key results – Syagrus harenae resembles S. glaucescens, but some characteristics easily differentiate it, such as the small size, lax pinnae, symmetric pinnae tips, ramenta scales, a scattered thin indumentum on the peduncle, inflorescences and fruits orangish-yellow, and pistil with indumentum. The new species also possesses flowers arranged in tetrads and pentads and is the first species of Syagrus showing two sepals, petals with imbricate tips, staminodes with anthers, and frequently lacks staminodial rings. The pinnae anatomy of the new species also resembles S. glaucescens, which indicates their relatedness. However, reliable differences in pinnae anatomy set the new species apart, such as the fibrous ring reaching the abaxial hypodermis and the large first adaxial fibre bundle near the margin. The new species is assessed as critically endangered.
Conclusion – Syagrus harenae is the first endemic species of the genus described for the Serra do Ambrósio and possesses striking characteristics, such as the re-greening of the pistillate flowers and flowers arranged in tetrads and pentads. The type population corroborates the Diamantina Plateau and its disjunctions as one of the centres of diversity for Syagrus. The discovery of this new species reinforces the uniqueness of the local flora and its classification as a priority area for conservation.
Keywords: campo rupestre, carrasco, Espinhaço Range, Palmae, Serra do Ambrósio, taxonomy
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| Syagrus harenae. A. Prostrated stem. B. Sheathing leaf arranged in 5 nearly vertical or slightly spiralled rows. C. Flowers arranged in tetrads. D. Sepals connate at the base. E. Flowers arranged in pentads. F. Fruits. G. Endocarp pores . A–G from Sant’Anna-Santos & Francino 406 (DIAM, holotype). Illustration by Gustavo Surlo. |
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| Vegetative morphological aspects of Syagrus harenae. A. Landscape photograph of the type locality: a group of individuals (white rectangles) growing on the sandy soils near rock outcrops (ro). B. The white arrowhead indicates the prostrated stem. C. Ramenta (black arrowheads) on the pinnae abaxial surface (ab) and leaf rachis with brownish tomentum (ra). D. Long tapering pinnae tips (white arrowheads). E. Pinnae: dark-green adaxial surface (ad) and glaucous abaxial surface (ab). F. Pinnae inserted in divergent planes over the rachis (rc). G. Fibres (white arrowheads) of the pseudopetiole. H. Leaf sheath (sh), peduncular bract (pb), and prophyll (pr). Photographs by Bruno F. Sant’Anna-Santos. |
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Floral morphology of Syagrus harenae. A. Staminate flowers on rachillae upper 1/3 and triads on its lower 2/3: staminate flowers in pre-anthesis (two black arrowheads). B. Tetrads (two white circles): staminate flowers in anthesis (two black arrowheads). C. Inflorescence bearing only pistillate flowers (after staminate flowers’ senescence). D. Triad: sessile staminate flowers, yellow pistillate flowers. E. Pedicellate staminate flowers (two black arrowheads), green pistillate flowers. F. Tetrad: two central pistillate flowers flanked by two staminate flowers. G. Pentad on lateral view: three central pistillate flowers flanked by two staminate flowers (two black arrowheads). H. Pentad: top view. Staminate flowers (two black arrowheads). I. Apex and base staminate flowers. Three petals (pe). J. Staminate flower: petals (pe) longer than ... Photographs by Bruno F. Sant’Anna-Santos Fruit morphology of Syagrus harenae. A. Infructescence. B. Immature fruit: epicarp green in colour and recovered by a scaly lepidote tomentum. C. Mature fruit: epicarp orange in colour and recovered by a scaly lepidote tomentum. D. Fibrous mesocarp (me). Epicarp (ep). Endocarp (en). E. Three apical endocarp pores: top view. F. Endocarp pore, lateral view. G. Longitudinal section: brownish endocarp (en) and whitish endosperm (ed). Photographs by Bruno F. Sant’Anna-Santos. |
Syagrus harenae B.F.Sant’Anna-Santos, sp. nov.
Diagnosis: Syagrus harenae is similar to S. glaucescens Glaz. ex Beccari, from which it differs by lax pinnae on the leaf rachis (vs congested pinnae), apical pinnae size (8–12 × 0.2–0.4 vs 1.5–6 × 0.2–1.0), pinnae with symmetrical tip (vs asymmetrical); base of the stem not-angular (vs angular), brownish indumentum where pinnae are inserted on the lower leaf rachis (vs glabrous); prostrated stem (vs erect); sheathing leaf base length (10–28 cm vs 42–52 cm), lax sheathing leaf base (vs congested); inflorescence strongly pendulous (vs erect ou slightly pendulous); peduncle with scattered thin indumentum (vs glabrous); petal tips imbricate (vs valvate); pistil with whitish indumentum on lower 1/3 (vs glabrous), inconspicuous staminodial ring (vs conspicuous staminodal ring); fruit yellowish-orange when mature (vs brownish).
Etymology: The specific epithet, harenae, means sand and refers to the unique sandy soil where the new species grows in the Serra do Ambrósio mountain.
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| Morphological aspects of Syagrus harenae with ecological implications. A. Fly on the peduncular bract. B. A bee visiting a pistillate flower. C. A bee visiting a staminate flower. D. Beetle. E–F. Larvae (two white arrowheads). G–H. Fruits and endocarps on the sandy soil. I. Mesocarp damaged (da) by fruit predation. J–K. Pendulous infructescences almost reaching the ground (three white circles), and young plants (two white arrowheads) near adult plants. Photographs by Bruno F. Sant’Anna-Santos. |
Bruno Francisco Sant’Anna-Santos, Elaine Lopes Pereira Nunes, Rafael Micheli and Dayana Maria Teodoro Francino. 2025. Hidden in the Mountain: A New rare Syagrus (Arecaceae) with morphological novelties. Plant Ecology and Evolution. 158(1): 63-81. DOI: doi.org/10.5091/plecevo.140657
