Revista de Biología Tropical ISSN: 0034-7744 ISSN: 2215-2075 Universidad de Costa Rica Rocha-Dantas, Adelson; Carneiro-Guedes, Marcelino; Vasconcelos, Caroline- da-Cruz; Lôbo-Isacksson, Jaynna-Gonar; Barbosa-Pastana, Dayane- Nathália; Lira-Guedes, Ana-Cláudia; Fernandez-Piedade, Maria-Teresa Morphology, germination, and geographic distribution of Pentaclethra macroloba (Fabaceae): a hyperdominant Amazonian tree Revista de Biología Tropical, vol. 69, no. 1, 2021, January-March, pp. 181-196 Universidad de Costa Rica DOI: https://doi.org/10.15517/rbt.v69i1.43446 Available in: https://www.redalyc.org/articulo.oa?id=44967852015 How to cite Complete issue Scientific Information System Redalyc More information about this article Network of Scientific Journals from Latin America and the Caribbean, Spain and Journal's webpage in redalyc.org Portugal Project academic non-profit, developed under the open access initiative ISSN Printed: 0034-7744 ISSN digital: 2215-2075 DOI 10.15517/rbt.v69i1.43446 Morphology, germination, and geographic distribution of Pentaclethra macroloba (Fabaceae): a hyperdominant Amazonian tree Adelson Rocha Dantas1*, Marcelino Carneiro Guedes2, Caroline da Cruz Vasconcelos3, Jaynna Gonar Lôbo Isacksson4, Dayane Nathália Barbosa Pastana5, Ana Cláudia Lira-Guedes2 & Maria Teresa Fernandez Piedade1 1. Programa de Pós-graduação em Ecologia, Instituto Nacional de Pesquisas da Amazônia, Manaus, Brasil; [email protected], [email protected] 2. Departamento de Recursos Florestais, Empresa Brasileira de Pesquisa Agropecuária, Macapá, Brasil; [email protected], [email protected] 3. Programa de Pós-graduação em Botânica, Instituto Nacional de Pesquisas da Amazônia, Manaus, Brasil; [email protected] 4. Grupo de Pesquisa em Ecologia Florestal, Instituto de Desenvolvimento Sustentável Mamirauá, Tefé, Brasil; [email protected] 5. Programa de Pós-graduação em Engenharia Florestal, Universidade Federal de Lavras, Lavras, Brasil; [email protected] * Correspondence Received 10-VIII-2020. Corrected 04-XI-2020. Accepted 13-XI-2020. ABSTRACT. Introduction: Pentaclethra macroloba is a hyperdominant tree in the Amazon estuary of great socioeconomic importance for the region because the oil from its seeds is a powerful herbal medicine. Objective: We aimed to characterize the morphological structure, the morphological adaptations in response to the daily flooding of the Amazon estuary and the biogeographic area of P. macroloba. Methods: Detailed description of the external morphology, from germination to the adult tree, was obtained from individuals located in floodplain forest, Northeast Amazonia. The occupation area and the geographical extension of P. macroloba were determined from point of geographical coordinates of botanical samples deposited in the digital collections of Mobot and SpeciesLink. Results: Adult individuals have adapted structures in response to daily flooding, such as: adventitious roots to increase respiratory efficiency and lenticels in the trunk, serving as a connection point for oxygen transport between the root and the aerial part. Dried fruit favours the activation of the explosive dehiscence mechanism, allowing the seed to be expelled long distance. Deltoid shape of the seed allows water fluctuation and more efficient dispersal. Seedling is phanerocotylar hypogeal and with one pair of reserve cotyledons that provide the seedling an extra source of energy to escape the flood. Germination rate was 78 % and the speed was 0.2 seeds.day-1. Circular buffer method revealed the presence of 123 subpopulations of P. macroloba distributed in a radius of 5 699 943 km² across the Neotropical region. Conclusions: Much of the morphological structures of P. macroloba are adaptive and evolutionary responses to the periodically flooded environment of the Amazon estuary, showing that these environments select the trees, best adapted, to inhabit the flood. P. macroloba has a wide geographical area denotes the plasticity of adapting to different environments, which may justify its monodominance in some regions. Key words: morphological adaptation; tidal flooding; Neotropical tree; adventitious roots; pracaxi oil; manage- ment, conservation. Rocha Dantas, A., Carneiro Guedes, M., da Cruz Vasconcelos, C., Lôbo Isacksson, J.G., Barbosa Pastana, D.N., Lira-Guedes, A.C., & Fernandez Piedade, M.T. (2021). Morphology, germination, and geographic distribution of Pentaclethra macroloba (Fabaceae): a hyperdominant Amazonian tree. Revista de Biología Tropical, 69(1), 181-196. DOI 10.15517/rbt.v69i1.43446 Rev. Biol. Trop. (Int. J. Trop. Biol.) • Vol. 69(1): 181-196, March 2021 181 Some tree species in the Amazon region the natural history of the population that lives have great dominance, occurring in a wide in the Amazon Basin (Hartshorn, 1983). area, others have isolated populations and P. macroloba is an important non-timber their distribution is restricted to a specific species in the local socioeconomic, source of environment (ter Steege et al., 2013). The income for several riverside Amazon, due to great challenge for many forest ecologists is to its multiple uses. The bark of the tree trunk has understand the mechanisms and strategies that triterpenoid saponins that have anti-haemor- trees develop over time to colonize the most rhagic action against the venom of snakes of varied environments in the Amazon rainforest. the Bothrops genus (Silva et al., 2007). The oil In the Amazon floodplain, the periodically extracted from the seeds is a powerful natural flooded environment can promote speciation medicine, which is very common riverside and adaptation processes in the trees that Amazon people to use this oil to treat muscle inhabit this environment. Various adaptations pain and inflammation. The oil has a high con- in the external morphology of the plants are centration of fatty acids that moisturize the skin observed in response to the low availability of (Costa et al., 2014), which is highly requested oxygen in the rhizosphere and the constant ero- by the cosmetics industry as raw material. Despite the great arboreal biodiversity of sion of the soil, such as high density of lenticels the Amazon, information on the basic morphol- in the trunk and the presence of roots and aerial ogy of plant species is still lacking, difficult structures: rhizophores, pneumatophores, haus- to understand the evolutionary adaptations of toria and buttresses (Almeida, Amaral, & Silva, trees to the environment. In addition, studies 2004; Parolin, 2012). of plant morphology are important to ensure In Central Amazonia, flooding in the for- the correct identification of trees and natural est can last up to 243 days and reach a height regeneration (Melo, Mendonça, & Mendes, of up to 6 m on the tree trunk (Schöngart, 2004), indispensable requirement in biodiver- Piedade, Ludwigshausen, Horna, & Worbes, sity inventory. 2002). Trees respond to this long period of Dispersion patterns of the trees has great flooding reducing metabolic activity, which in contribution to the diversification of the Ama- many cases leads to leaf fall in the canopy (De zon rainforest (Gentry, 1981). The biogeo- Simone, Junk, & Schmidt, 2003) and formation graphic patterns of trees are the result, in many of annual rings on the trunk (Schöngart et al., cases, of limited dispersion (Wiens, 2011) 2004). However, in the Eastern Amazon, the and reveal characteristics of its ecology and knowledge of the morphological and ecophysi- evolutionary biology (Gaston & Fuller, 2009), ological adaptations of tree species that grow important knowledge for conservation strate- under the regime of daily flooding and low gies of species that have economic potential, amplitude of the Amazon estuary (Junk et al., such as P. macroloba. 2011) is still quite modest. In this study, we evaluated the morpho- The floodplains of the Amazon estuary logical adaptations of P. macroloba in response have several endemic and dominant species as to the daily flooding of the Amazon estuary. We Pentaclethra macroloba. Species of the Faba- provide a detailed description of the external ceae family, popularly known by name “pra- morphology of P. macroloba and evaluate its caxi” (Dantas, Marangon, Guedes, Feliciano, & biogeographic area to assist in the management Lira-Guedes, 2017). This species is hyperdomi- and conservation of this species. nant Amazon (Ter Steege et al., 2013) and large occurrence in Amazon estuary (Carim, Wit- MATERIALS AND METHODS tmann, Piedade, Guimarães, & Tostes, 2016). Among the three populations of P. macroloba Study area: Botanical material was in Neotropical America, little is known about collected from individuals located in two 182 Rev. Biol. Trop. (Int. J. Trop. Biol.) • Vol. 69(1): 181-196, March 2021 floodplain areas: Mazagão Experimental Field and morphological description was conducted, (CEM) and Fazendinha Environmental Pro- through a specialized form with botanical tection Area (APA da Fazendinha hereafter), terms. After the description, exsiccates were State of Amapá, Brazil. CEM belongs to the prepared for deposit in the Embrapa Herbarium Brazilian Agricultural Research Corporation, Amazônia Oriental - IAN, Belém, Pará (regis- located in the city of Mazagão (00°02’33” S tration numbers IAN192676 and IAN192677). & 51°15’24” W), it has 55.95 ha of floodplain Morphological structures of the trunk, forest and is bathed by the tributary of the branches, leaves, flowers, fruits, seeds and Amazon River called “furo do Mazagão”. The