Filling a distribution gap: a new record of Pradosia ptychandra (Sapotaceae) from eastern Brazilian Amazonia

Preenchendo uma lacuna de distribuição: um novo registro de Pradosia ptychandra (Sapotaceae) para a Amazônia oriental brasileira

ABSTRACT

Based on fertile material collected in January 2019, we report the first record of Pradosia ptychandra (Sapotaceae, Chrysophylloideae) to the flora of Amapá state, eastern Brazilian Amazonia. This new record fills a geographical gap between its previously known occurrences in the Guiana Shield and central Amazonia, improving our knowledge of its distribution pattern. We also provide comments on the taxonomy, preliminary conservation status, and current distribution of the species, in addition to an illustrative plate on its morphology and habitat.

KEYWORDS:
Chrysophylloideae; flora of Amapá; conservation status; new occurrence; taxonomy

RESUMO

Com base em material fértil coletado em janeiro de 2019, relatamos o primeiro registro de Pradosia ptychandra (Sapotaceae, Chrysophylloideae) para a flora do estado do Amapá, Amazônia oriental brasileira. Esse novo registro preenche uma lacuna geográfica entre suas ocorrências anteriormente conhecidas no Escudo das Guianas e na Amazônia central, ampliando nosso conhecimento sobre seu padrão de distribuição. Também fornecemos comentários sobre a taxonomia, o estado preliminar de conservação e a distribuição atual da espécie, além de uma prancha ilustrativa sobre sua morfologia e habitat.

PALAVRAS-CHAVE:
Chrysophylloideae; flora do Amapá; estado de conservação; nova ocorrência; taxonomia

Despite being home to the world’s most biodiverse tropical forest, the Amazon biome is currently highly threatened by climate change and deforestation (Gomes et al. 2019; Stropp et al. 2020). Biodiversity studies have increased considerably in this region, but many areas remain scientifically neglected and poorly documented from a floristic perspective (Carvalho et al. 2023).

Estimates suggest 6,000 to 16,000 tree species with diameter at breast height ≥ 10 cm in Amazonia (Cardoso et al. 2017; ter Steege et al. 2020). Approximately 280 tree species can be recorded in a single hectare of terra-firme (non-flooded) forest in central Amazonia (Oliveira and Mori 1999). These numbers are impressive and likely underestimated, as new tree species are frequently revealed in the biome (Vasconcelos et al. 2021b; Mouzinho et al. 2022; Costa et al. 2023).

In January 2019, during a field expedition conducted in a remote area in the southern portion of Amapá state, in the extreme northeast of Brazilian Amazonia, we collected samples of a flowering tree of Pradosia Liais (Sapotaceae) in a terra-firme forest at the confluence of the rivers Maracá-Parú and Igarapé Grande in the municipality of Mazagão. After examining the morphological, ecological, and geographic characteristics of Pradosia species, the samples were identified as Pradosia ptychandra (Eyma) T.D.Penn., the first record of this tree species for eastern Brazilian Amazonia.

Pradosia forms a monophyletic lineage within the Neotropical Chrysophylloideae, distinguished by a rotate corolla with a short tube, absence of staminodes, a drupaceous fruit with plano-convex cotyledons, an exserted radicle below the cotyledons, and the absence of endosperm (Terra-Araujo et al. 2015; Faria et al. 2017; Swenson et al. 2023). It comprises 24 species of trees and shrubs growing in moist and dry tropical forests throughout Central and South America (Pennington 1990; Terra-Araujo et al. 2016; Fernández et al. 2022). The highest diversity of Pradosia is found in Amazonia (10 species) and the Atlantic Forest (6 species) (Alves-Araújo and Alves 2012; Terra-Araujo et al. 2016).

Pradosia ptychandra was first recorded in Suriname (Eyma 1936), and its known distribution comprises the Guiana Shield (Guyana, Suriname, and French Guiana) and central Amazonia (Brazil). This sparse and patchy distribution can reflect gaps in botanical sampling, particularly in remote areas (Nelson et al. 1990; Hopkins 2007; Schulman et al. 2007). Limited knowledge of species distributions results from many factors, including low collection intensity, scarcity of adequate taxonomic studies, and unreliable species identification. Species with narrow distributions or those rarely collected, for example, may result from misidentifications, irregular blooms, or occurrence in areas historically unexplored by botanists (Hopkins 2019).

We deposited the examined material at the INPA herbarium (acronym follows Thiers 2024). We identified the material using a Leica& #174;S8APO stereomicroscope (coupled to a Leica DFC295 camera), following descriptions of Pennington (1990) and Terra-Araujo et al. (2016). We used web-based resources such as the Reflora Virtual Herbarium (https://reflora.jbrj.gov.br/reflora/herbarioVirtual/), SpeciesLink (https://specieslink.net/search/), and Global Biodiversity Information Facility (https://www.gbif.org/) to search records of P. ptychandra. The pre-processed and geo-referenced dataset (20 unique occurrences) was imported into the ConR package (Dauby et al. 2017) using the R environment (R Core Team 2022) to assess conservation status based on IUCN Red List Categories and Criteria (IUCN 2012, 2022). We estimated the extent of occurrence (EOO), area of occupancy (AOO; 2-km² grid) and the number of subpopulations. A species distribution model was used to predict the current potential distribution of P. ptychandra, following Vasconcelos et al. (2021a). We prepared the final map using QGIS v.3.28.1 (QGIS Development Team 2022).

Pradosia ptychandra (Eyma) T.D.Penn.

(Figures 1 and 2)

New record: BRAZIL. Amapá: Mazagão, BR-156, ramal do Assentamento Maracá, Comunidade Caranã do Maracá, confluência entre os rios Maracá-Pacú e Igarapé Grande, floresta de terra-firme (submontana), 0°01’23.4”S, 51°56’40.0”W, 70 m alt., 13 Jan 2019 (fl.), C.C. Vasconcelos & B.F. Vasconcelos-Filho 176 (INPA 298002).

Figure 1
Pradosia ptychandra. A - Branch; B - Apical bud; C - Leaf (lower and upper surface); D - Tertiary leaf venation; E - Midrib (lower surface); F - Petiole; G - Fascicle of flowers; H - Flower bud (oblique-top view); I - Flower bud (longitudinal section); J - Part of open corolla exposing a stamen; K - Gynoecium; L - Panoramic view of the Maracá-Pacú River in Amapá state.

Figure 2
Distribution map of Pradosia ptychandra, showing previous records (black transparent circles) and a new record (black transparent star). The color gradient indicates habitat suitability.

Medium-sized tree 11 m tall. Trunk 30 cm DBH, cylindrical. Bark grayish-brown, smooth. Latex whitish, copious. Leaves clustered, spirally arranged, 8.0-16.3 × 2.0-5.5 cm long, predominantly obovate, discolorous, glabrous; base cuneate or attenuate; apex cuspidate; margin entire and non-revolute; venation eucamptodromous, midrib sunken on the upper surface and with appressed indument on the lower surface (visible only with lens); secondaries in 11-13 pairs, parallel (50-60°); intersecondaries absent; tertiaries oblique. Petiole 0.8-2.0 cm long, strongly canaliculate, glabrescent, and without scales. Fascicles many-flowered, ramiflorous (twigs or larger branches). Flowers 5-merous; pedicel 9.9-12.7 mm long, densely appressed-tomentulose. Calyx quincuncial, sepals suborbicular, 1.8-2.3 mm long, sparsely tomentulose outside, glabrous inside. Corolla ca. 5.4 mm long, wine-red (in fresh material), densely appressed-tomentulose outside, glabrous inside; tube 1.3-1.8 mm long, lobes narrowly ovate. Stamens fixed near the top of the corolla tube; filaments 1.3-1.9 mm long, glabrous; anthers 1.2-1.5 long, glabrous. Ovary 5-locular, 1.4-2.0 mm long, conical, densely strigose; style 0.8-1.1 mm long, glabrous; stigma simple.

Pradosia ptychandra belongs to the “red-flowered” clade, recognized by non-sweet bark, leaves with sunken midrib, reddish or wine-red flowers, and larger corolla (Terra-Araujo et al. 2015). Some species in this clade also have cauliflory, scales attached at the middle of the petiole, and fruits with muricate exocarp as diagnostic features (Terra-Araujo et al. 2015, 2016). Pradosia ptychandra could be confused with P. lactescens (Vell.) Radlk. and P. lahoziana Terra-Araujo by the similar foliage, presence of wine-red flowers, and cauliflory; however, they can be distinguished by several characteristics (Table 1).

Table 1
Comparisons between Pradosia ptychandra and its morphologically related species. Information following Pennington (1990) and Terra-Araujo et al. (2015, 2016).

Characteristic	P. ptychandra	P. lahoziana	P. lactescens
Known geographic distribution	central and northeastern Amazonia	central Amazonia	Atlantic Forest
Soil type	clayish	sandy or occasionally clayish	clayish
Altitude (m)	70-770	50-125	~980
Buttress roots	usually absent or poorly developed	absent	present
Secondary venation (cross-section)	slightly sunken above	slightly raised or flat above	slightly sunken above
Pairs of secondary veins	10-13	≥ 13	7-12
Scales on the petiole	absent	present	absent
Pedicel length (mm)	≥ 7.0	≥ 7.0	≤ 6.0
Corolla length (mm)	5.0-5.5	≥ 6.4	4.8-6.5
Corolla indumentum	sparsely tomentulose outside	glabrous outside	usually glabrous outside
Fruit length (cm)	2.5-4.0	≤ 3.0	3.0-4.5
Fruit indumentum	glabrous	tomentulose	glabrous

Considering the currently known range of P. ptychandra, 14 subpopulations were identified with EOO = 508,780 km², AOO = 68 km², and 15 locations (five within protected areas, two in French Guiana, two in Suriname, and one in Brazil). Habitat loss by deforestation, anthropogenic fires, and logging and mining activities are potential threats in this region (Funi and Pase 2012; Dezécache et al. 2017; Siqueira-Gay et al. 2020; Jébrak et al. 2021; Santana et al. 2023). Moreover, given the relatively narrow area of occupancy and few locations within protected areas, this species qualifies under the Near Threatened NT [B1a+B2a] conservation status (IUCN 2012, 2022).

When consulting the species-level unidentified specimens of Pradosia from Amapá in the SpeciesLink database, we observed that specimen H. Medeiros et al. 3223 (INPA 282538) collected in the Tumucumaque National Park is likely to be P. ptychandra because of its foliage resemblance. However, the specimen is sterile, which currently prevents us from making a definitive identification. In any case, our new record from Amapá contributes to fill a gap in the previously known distribution range of this species. Our ensemble distribution model indicates that the suitable habitat for P. ptychandra occurs predominantly in northeastern Pan-Amazonia (Guiana Shield and Amapá in Brazil), as well as patches towards eastern and central Amazonia in Pará and Amazonas states, respectively (Figure 2). The temperature annual range (difference between maximum temperature of warmest month and minimum temperature of coldest month) (10-11.6 °C), wind speed (1.2-2.5 m s^-1), precipitation (104-303 mm), and maximum temperature (29.2-30.1 °C) are important climate parameters affecting the distribution of suitable habitat for P. ptychandra.

This study reinforces the importance of targeting botanical collecting efforts in remote and undersampled areas in Amazonia, such as Amapá state. We recommend prioritizing gap regions in species distributions, actively searching areas where the species presence is predicted by models. This strategy has the potential of significantly forwarding our knowledge about species distribution and discovery of new species in the Amazon.

ACKNOWLEDGMENTS

The authors thank the Programa de Pós-Graduação em Botânica (PPGBOT) of Instituto Nacional de Pesquisas da Amazônia (INPA), Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES, finance code 001), and Fundação de Amparo à Pesquisa do Estado do Amazonas (FAPEAM) for financial support, and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, process 142214/2018-3) for the doctoral scholarship granted to CCV. We are grateful to the team of the INPA herbarium, especially Michael Hopkins and Jaqueline Gomes; and the team of the Seed Laboratory for their overall support, especially Gabriel Jaquetto. CCV thanks Marcelino Guedes and Ana Lira-Guedes for kindly providing the infrastructure of Embrapa Amapá to prepare the samples; and her father, Benedito Vasconcelos-Filho, who accompanied her on the adventure that led to this discovery. We also thank the editors and reviewers for their insightful comments.

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• CITE AS:

  Vasconcelos, C. C.; Diele-Viegas, L.M.; Camargo, J.L.C.; Ferraz, I.D.K.; Terra-Araujo, M.H. 2024. Filling a distribution gap: a new record of Pradosia ptychandra (Sapotaceae) from eastern Brazilian Amazonia. Acta Amazonica 54: e54bc23421.

Data availability

The data that support the findings of this study are available, upon reasonable request, from the corresponding author, Caroline da Cruz Vasconcelos.

Edited by

ASSOCIATE EDITOR:

Natália Ivanauskas

Publication Dates

• Publication in this collection
  08 July 2024
• Date of issue
  Apr-Jun 2024

History

• Received
  13 Jan 2024
• Accepted
  27 May 2024