Syagrus harenae B. F. Sant'Anna-Santos 2025, sp. nov.
Creators: name: Sant'Anna-Santos, Bruno Francisco
name: Lopes Pereira Nunes, Elaine
name: Micheli, Rafael
name: Maria Teodoro Francino, Dayana
Publisher: name: Zenodo
Year: 2025
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Liliopsida
Arecales
Arecaceae
Syagrus
Syagrus harenae

description: Syagrus harenae B. F. Sant’Anna-Santos sp. nov.
Figs 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, Tables 1, 2
Type.
BRAZIL – Minas Gerais • Itamarandiba, Vilarejo de Penha da França; 18°2’44.76”S, 43°4’45.02”W; 1000 m; 15 Feb. 2024; fl., fr.; Sant’Anna-Santos & Francino 406; holotype: DIAM; isotypes: UPCB, IBGE, HCF.
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).
Description.
Small to moderate-sized palm, solitary, 110–160 (– 250) cm tall. Stem 40–110 (– 140) × 15–25 cm, prostrate, with persistent leaf bases arranged in rows with indistinct internodes near the crown, non-angular stem base. Leaves pinnate number 8–15; sheathing leaf base ca 10–28 cm long; pseudopetiole 15–37 cm long; petiole 9–27 × 0.5–1.6 cm and 0.2–0.7 cm thick, rachis 95–167 cm long; abaxial side of petiole and rachis with brownish tomentum; pinnae medium to dark-green, discolourous, abaxial surface glaucous, linear, rigid-coriaceous with apex more or less symmetrical and long tapering, pinnae numbering 63–79 pairs, in clusters of 2–5, lax on leaf rachis, inserted in divergent planes over the rachis; pinnae with inconspicuous ramenta scales along the abaxial midrib (near the rachis) on young leaves; basal pinnae 27–36 × 0.4–0.6 cm, middle pinnae 17.5–30.5 × 1.7–2.3 cm, apical pinnae 8–12 × 0.2–0.4 cm. Inflorescences pendulous, spirally branched, prophyll 11–16 (– 26) × 1.3–2.5 cm; peduncular bract 56–72 cm long, inflated portion 25–31 × 5.2–7.5 cm, including a 1.0– 1.4 cm beak, 6.4–8.5 cm perimeter, 2–3 mm thick, woody, sulcate, exterior glabrous; peduncle 30–41.5 cm long, 8–10 × 4–7 mm wide, with brownish scarce indumentum; inflorescence axis 19.5–24 cm long; rachis 1.5–13.3 cm long; rachillae 3–15, glabrous, yellow, 8.5–20 cm long at the apex, 12–17 cm long at the base; flowers arranged in triads, tetrads (with two central pistillate flowers, each flanked by a staminate flower) or pentads (with three central pistillate flowers flanked by two staminate flowers), staminate flowers with three sepals and three petals, and pistillate flowers with three sepals and three petals, two sepals and four petals, three sepals and four petals. Staminate flowers 9–10 × 4–5 mm at the apex, 11.5–14 × 4–6 mm at the base, those at the apex sessile, sometimes pedicellate, pedicels 1–4 mm long, yellowish-orange, sepals 1.5–3.5 × 1.5–2.5 mm, glabrous, triangular, no visible nerves, keeled, connate at the base, petals 8–10 × 2.5–4.0 mm at the apex, 9–19 × 3.5–4.5 mm at the base, with acute tips, slightly nerved; ovate-triangular, valvate, stamens 5–7 mm long; anthers 4–7 mm long, basally sagittate; filaments 2–3 mm long, free at the base, dorsifixed at the base (basifixed); pistillode trifid, ca 0.8–1.0 mm. Pistillate flowers elongate-pyramidal, 13–17 × 6–7 mm, orangish-yellow when immature and green when mature, glabrous; sepals 13–16 × 5–7 mm, orangish-yellow when immature and green when mature, without visible venation, triangular, imbricate; petals 10–13.5 × 3–5 mm, orangish-yellow when immature and green when mature, imbricate, triangular; pistil 6–8 × 3–4 mm, with whitish indumentum from the base of the pistil to nearly the base of the stigmas, stigmas 3– 3 mm long, glabrous; inconspicuous staminodial ring rarely present, less than 0.5 mm in height, staminodes arranged in pairs or isolated (sometimes with anthers), six in number, ca 1.0– 1.8 mm in height. Fruits ellipsoid, 2.1–3.0 × 1.6–2.0 cm, orange when mature, scaly lepidote tomentum, epicarp less than 0.5 mm thick, mesocarp less than 0.5 mm thick, succulent, and fibrous; endocarp 1.8–2.0 × 1.2–1.9 cm, 2–3 mm thick on the sides, 4–5 mm thick on the tips, trivittate interior. Seeds more or less ellipsoid, endosperm homogeneous. Germination remote tubular.
Distribution.
The type population of Syagrus harenae was found in the village of Penha de França, in the Serra do Ambrósio mountain (Fig. 1 A – E).
Habitat.
The Serra do Ambrósio mountain is characterised by forest formations at its base, which end abruptly at an altitude of around 900 meters, giving way to open vegetation types, such as the carrascos (Meguro et al. 1994). The steepness of the slope, the thickness of the colluvial deposits and the texture of the sandy soils are the main factors determining the vegetation type found on these slopes (see Meguro et al. 1994; Pirani et al. 1994). In this transitional environment, the coarse white sand deposited by rainwater drainage derives from quartzite rocks (Meguro et al. 1994; CODEMIG 2012; Costa et al. 2016) and is the substrate of the area where the new species was discovered.
In areas with a gentle slope and sand deposition, at an altitude range of 800–1200 m, the vegetation is known as carrasco and is characterised by very ramified scrawny bushes, ranging from an open to dense physiognomy (Pirani et al. 1994; Oliveira et al. 2014). The new species is more abundant in the carrasco with dense physiognomy (Figs 3 A, 7 A – B, 8 G, J – K). Costa et al. (2016) state that “ sandy soils are common in the Espinhaço Range, but those in Serra do Ambrósio have a different granulometry ”.
The climate of Serra do Ambrósio is Cwb according to the climatic classification of Köppen (1948), attenuated by altitude, with distinct wet and dry seasons, mean annual temperatures of 14.1–23.8 ° C and a mean annual rainfall of 1405 mm (Meguro et al. 1994). However, the air temperature at noon attains 30 ° C with air humidity at 40–50 %, while 2 cm below the sandy soil surface the temperature can reach 40–50 ° C (Meguro et al. 1994). Where the vegetation is denser on the carrasco, the larger shrubs shade the herbaceous and low subshrubby species, and the sandy soil is partially or entirely covered by the leaf litter (Figs 3 A – B, 8 G, J – K). Besides retaining moisture, the leaf litter might reduce the soil temperature and release organic matter, favouring the greater number of S. harenae specimens observed in these places (Figs 3 A – B, 7 A – B, 8 G – H, J – K).
The high floristic diversity in the carrasco includes species with large distribution (Pirani et al. 2014), such as Ananas ananassoides (Baker) L. B. Sm. (Fig. 7 C), a common species throughout Brazil (Reflora 2024). Moreover, species characteristic of other mountains in the Espinhaço Range, such as Kielmeyera regalis Saddi. (Figs 3 A, 7 B) and Pilosocereus aurisetus (Werderm.) Byles & G. D. Rowley (Fig. 7 D – E) are also common in the carrascos of Serra do Ambrósio. However, the flora in Serra do Ambrósio is also characterised by the presence of rare species (Pirani et al. 1994; Costa et al. 2018), such as Uebelmannia gummifera (Backeb. & Voll) Buining (Fig. 7 F). The Serra do Ambrósio mountain should be highlighted as an outstanding conservation area for other botanical families, especially Eriocaulaceae (see Oliveira et al. 2014; Costa et al. 2016). To date, endemic species of Eriocaulaceae have been recognised for the Serra do Ambrósio (Pirani et al. 1994; Costa et al. 2016).
Ecology.
After peduncular bract opening, the orangish-yellow flowers of S. harenae are prominent in the subshrub layer of the denser carrasco (Figs 7 A, 8 A – C, E). The staminate flowers remain orangish-yellow until they fall off (Figs 4 A – H, M, 5 A, 8 A – C, E, G). On the other hand, the pistillate flowers transition from yellow to green over time (Figs 4 A – H, M, 5 A, 8 A – C, E). Soon after the anthesis of the peduncular bract, the flowers are visited by flies (Fig. 8 A), stingless bees (Fig. 8 B – C), and beetles (Fig. 8 D). In S. harenae, the beetles and their larvae intermingle among the flowers, covered in pollen grains (Fig. 8 D – F).
Palms are well-known as hotspots for insect abundance and diversity, but so far for Syagrus, the evidence points to pollination both by beetles and bees (Silberbauer-Gottsberger et al. 2013; Núñez-Avellaneda et al. 2015; Guerrero-Olaya and Núñez-Avellaneda 2017; Núñez-Avellaneda and Carreño 2017). According to Medeiros et al. (2019), beetles breed on floral tissues of S. coronata as larvae. Besides pollen, nectar is another floral reward associated with Syagrus (Silberbauer-Gottsberger et al. 2013). In addition, the presence of osmophores in pistillate flowers has already been recorded for the genus (see Sant’Anna-Santos et al. 2023 a). In S. harenae, nectar drops were not observed, a strong sweet odour was released, and the visit of bees to both pistillate and staminate flowers may indicate that they are looking for a resource other than just pollen (Fig. 8 B – C). However, future studies will be necessary to identify which secretory structure is associated with offering rewards to pollinators and verify the presence of osmophores or nectaries in S. harenae.
In Syagrus, most species display flowers in shades ranging from green to yellow (see Noblick 2017 a), but the re-greening of flowers after anthesis is rare. This phenomenon has only been documented twice: first in Syagrus coronata (Mart.) Becc. (Medeiros et al. 2019) and now in Syagrus harenae. Flower colour changes after anthesis (e. g. Weiss 1995; Lunau 1996; Nadot and Carrive 2021) due to ageing or pollination, though observed across various plant taxa, are relatively uncommon (Ruxton and Schaefer 2016) and are often seen as signals to pollinators (Weiss 1995). Notwithstanding, Ruxton and Schaefer (2016) argue that there is limited evidence that floral colour change is sufficiently beneficial in modifying pollinator behaviour to evolve and be maintained.
Re-greening after anthesis, while rare in flowers, has been reported in some species (see Weiss 1995; Knapp et al. 2001; Medeiros et al. 2019; Sun et al. 2021). It is more common in extrafloral organs, where it may provide energy for seed development (Pélabon et al. 2015) and, in a Zantedeschia hybrid, was due to the masking of carotenoids by chlorophyll (Chen et al. 2009). In S. harenae and S. coronata, the re-greening occurs in entire pistillate flowers, which may point to a dual strategy: signalling pollinators while contributing to energy production. The occurrence of dimorphism in floral colours (sexual dichromatism) in two species of Syagrus warrants further studies to investigate its role in the group’s evolution.
On the soil, next to the specimens of S. harenae, it is noticeable that many fruits from different reproductive periods are deposited just below the infructescences where they were produced (Fig. 8 G – I). As they ripen, the fruits increase in weight, and the infructescence draws closer to the ground (Fig. 8 J – K), where the fruits complete their ripening and fall. The large number of fruits close to the mother plant, with the mesocarp only partially consumed (Fig. 8 G – I), provides evidence that animals feeding on these fruits are either not able to swallow or are not able to carry their seeds. In addition, it was very common to observe young plants next to the mother plant (Fig. 8 J – K).
For rare species such as S. harenae, natural selection would probably favour limited dispersal where drivers such as environmental conditions, surrounding vegetation and ineffective dispersal would be relevant causes of philomatry (Cheplick 2022). According to this author, the mother-site hypothesis (MSH) proposes that the selection should favour philomatry in a population adapted to a particular habitat because offspring will likewise be adapted to that same habitat. Philomatry can be applied to a plant species with limited spatial dispersal and a tendency for their offspring to remain in the site where they were produced (Cheplick 2022). Therefore, MSH can at least partly explain the several rare species of Syagrus along the Espinhaço Range and should be further explored to understand the ecology and evolution of these species.
Phenology.
The new species was collected with flowers and fruits in February 2024.
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.
Preliminary IUCN conservation assessment.
The population of the new species has only been recorded in the Serra do Ambrósio mountain, where there is no conservation unit. Close to the type population, there is a mining site for sand extraction, which has been closed. Sand extraction has also been recorded in other parts of Serra do Ambrósio (see Costa et al. 2018: fig 4 a). Taking into account the area of occupancy (AOO = 12 km 2) and the extent of occurrence (EOO = 1.231 km 2), and according to the IUCN (2022) categories and criteria, S. harenae should be considered Critically Endangered (CR): B 1 ab (i, iii).
Additional specimens examined.
BRAZIL – Minas Gerais • Rio Vermelho, Pedra Menina, Serra do Ambrósio, Morro da Virada do Mato Virgem; 31 Jul. 1985; fl.; Mello-Silva et al. 7833; SPF • Penha da França, ca 100 km ao nordeste de Diamantina; 18°4’48”S, 43°4’48”O; 11 Mar. 1995; Splett 875; UB.
Pinnae anatomy.
Stomata occur only on the abaxial surface (Fig. 9 A – B), with guard cells located at the same level as ordinary epidermal cells (Fig. 9 B). In the transverse section of the pinnae, the subsidiary cells are arciform and located entirely beneath the cuticle level (Fig. 9 B). The hypodermis on both surfaces of the pinnae consists of one to two layers of cells that are elongated longitudinally or have a quadrangular shape (Fig. 9 A – B). The hypodermis forms two layers between the adaxial non-vascular fibre bundles (Fig. 9 A). On the abaxial surface, the hypodermis is interrupted by substomatal chambers (Fig. 9 B). Tiny fibres and rounded groups with a larger number of fibres are observed in the abaxial hypodermis (Fig. 9 C – E). Large fibre bundles are connected to the adaxial hypodermis and reach nearly ½ across the mesophyll (Fig. 9 E). The primary vascular bundles are connected to the adaxial hypodermis and are always entirely surrounded by fibres (Fig. 9 E, H). The primary vascular bundles always have a larger diameter, two phloem poles, and noticeable protoxylem and metaxylem elements (Fig. 9 E). The secondary and tertiary vascular bundles are only abaxially surrounded by a sclerenchymatous sheath (Fig. 9 C, E – G, I). While the secondary vascular bundles are non-connected to the abaxial hypodermis, the tertiary vascular bundles are connected to the abaxial hypodermis (Fig. 9 C, E – G, I). The mesophyll is dorsiventral, with four to six bands of palisade parenchyma near the hypodermis on the adaxial surface and 10 to 12 chlorenchyma layers adjacent to the abaxial surface (Fig. 9 I). Regarding the margin, there is a large first adaxial non-vascular fibre bundles and, sometimes, a tertiary vascular bundle connected to the adaxial hypodermis (Fig. 9 I). The midrib is transversally triangular and adaxially projected, and the expansion tissue is interrupted and packed with fibre groups (Fig. 9 J – K). The main vascular system of the midrib consists of five collateral bundles, surrounded by a fibrous ring and 1 accessory bundle with a reinforced sheath connected to the adaxial hypodermis (Fig. 9 J, N). There are 2–4 non-vascular fibre bundles around the fibrous ring (Fig. 9 M). Table 2 compares the pinnae anatomy of S. harenae, S. aristeae, S. duartei, S. evansiana, and S. glaucescens.
Notes.
All the known species in the Syagrus glaucescens complex occur in neighbouring regions of the Espinhaço Range in the state of Minas Gerais (Fig. 1 A): Serra do Cipó, Diamantina Plateau, Serra do Cabral massif, and northern mountains complex (Noblick 2017 a; Firmo et al. 2021; Sant’Anna-Santos et al. 2023 c). Syagrus glaucescens Glaz. ex. Becc. is one of the rupicolous species found mainly on the Diamantina Plateau (see Fig. 1 A). To the south of the Diamantina Plateau, in the region known as Serra do Cipó, Syagrus duartei Glassman was the second species described for the complex (see Glassman 1968), and perhaps the most controversial. Also rupicolous, in the Flora Palmae da Serra do Cipó by Marcato and Pirani (2001), the authors did not recognise a morphological basis to support S. duartei as a species distinct from S. glaucescens. In fact, S. duartei is similar to S. glaucescens, and they are likely related and probably sympatric in the northernmost portion of the Serra do Cipó (Noblick 2017 a; SpeciesLink Network 2024). However, Marcato and Pirani (2001) did not consider anatomical data from Glassman (1972), which supported the species as distinct taxa – which was later corroborated by Noblick (2010, 2017 a).
The third species in the complex, the dwarf Syagrus evansiana Noblick, is more easily differentiated from S. duartei and S. glaucescens by characteristics such as acaulescence, leaves not arranged in vertical rows, spiciform inflorescences (not just branched) and the rare variation of 3 to 5 pores in the endocarp (Noblick 2009; 2010; 2017 a; Sant’Anna-Santos et al. 2023 c). Populations of S. evansiana have been recorded along the Espinhaço Range, such as in the disjunct Serra do Cabral and Serra do Ambrósio (see Noblick et al. 2014; Noblick 2017 a; Firmo et al. 2021; SpeciesLink Network 2024). In Serra do Cabral, morphological and anatomical studies showed that although similar to S. evansiana, the population was a fourth distinct species for the complex – the also dwarf and rupicolous Syagrus aristeae Sant’Anna-Santos (Firmo et al. 2021; Sant’Anna-Santos et al. 2023 c). The discovery of S. aristeae raised the suspicion that other populations thought to be S. evansiana, but without a greater collection effort and detailed morphoanatomical studies, could be unresolved species. Especially in the case of disjunct mountains with records of rare and microendemic species – such as the Serra do Ambrósio (see Costa et al. 2016).
The first record in the Serra do Ambrósio dates back to 1985, viz. Mello-Silva et al. 7833 (Pirani et al. 1994; SpeciesLink Network 2024). Although identified as S. glaucescens, the specimen has a very short stem, a characteristic of S. evansiana. A decade later, a second S. glaucescens was recorded in the Serra do Ambrósio. However, 20 years after the collection, the identity of Splett 875 was changed to S. evansiana and the Serra do Ambrósio was then included as an area of occurrence for both species (see Noblick 2017 a; SpeciesLink Network 2024).
description: Published as part of Sant'Anna-Santos, Bruno Francisco, Lopes Pereira Nunes, Elaine, Micheli, Rafael & Maria Teodoro Francino, Dayana, 2025, Hidden in the mountain: a new rare Syagrus (Arecaceae) with morphological novelties, pp. 63-81 in Plant Ecology and Evolution 158 (1) on pages 63-81, DOI: 10.5091/plecevo.140657