Santos IAWAet al. –Journal Wood anatomy 34 (3), 2013:of selected 313–323 Myrtaceae 313 WOOD ANATOMY OF MYRCIARIA, NEOMITRANTHES, PLINIA AND SIPHONEUGENA SPECIES (MYRTEAE, MYRTACEAE) Gabriel U.C.A. Santos1,*, Cátia H. Callado2, Marcelo da Costa Souza3 and Cecilia G. Costa4 1 Colégio Pedro II, CSCII, Campo de São Cristóvão 177, 20921-440 São Cristóvão, Rio de Janeiro, RJ, Brazil 2Universidade do Estado do Rio de Janeiro, Departamento de Biologia Vegetal, Instituto de Biologia Roberto Alcantara Gomes, Rua São Francisco Xavier 524, PHLC - sala 224, 20550-900 Maracanã, Rio de Janeiro, RJ, Brazil 3Museu Nacional / UFRJ, Departamento de Botânica, Quinta da Boa Vista, 20940-040 São Cristóvão, Rio de Janeiro, RJ, Brazil 4Instituto de Pesquisas Jardim Botânico do Rio de Janeiro, Laboratório de Botânica Estrutural, Rua Pacheco Leão 915, 22460-030 Jardim Botânico, Rio de Janeiro, RJ, Brazil *Corresponding author; e-mail: [email protected] absTracT Myrciaria, Neomitranthes, Plinia and Siphoneugena are closely related genera whose circumscriptions are controversial. The distinctions between Myrciaria vs. Plinia, and Neomitranthes vs. Siphoneugena, have been based on a few fruit characters. The wood anatomy of 24 species of these genera was examined to determine if wood anatomical features could help delimit the genera. It was determined the four genera cannot reliably be separated by wood anatomy alone. Characteristics seen in all four genera are: growth rings usually poorly-defined; diffuse porous; exclusively solitary vessels, usually circular to oval in outline; simple perforation plates; vessel-ray pits alternate and distinctly bordered; fibers with distinctly bordered pits in radial and tangential walls, usually very thick- walled; vasicentric tracheids typically absent; scanty paratracheal parenchyma, sometimes unilateral, and diffuse to diffuse-in-aggregates; chambered crystal- liferous axial parenchyma in many species, usually both prismatic and smaller crystals; rays 1–4-seriate, uniseriate rays composed of upright/square cells, multiseriate rays with procumbent body cells and 1 to many marginal rows of upright/square cells; disjunctive ray parenchyma cells usually present. Key words: Comparative wood anatomy, generic boundaries, South American Myrteae, Plinia group. INTRODUCTION Myrtaceae has 132 genera and 5671 species, of which 49 genera and c. 2500 species are in the tribe Myrteae (Lucas et al. 2007). The Myrteae comprises trees or occasional- ly shrubs and has a Pantropical distribution (Lucas et al. 2007), with high species diversity occurring along the eastern coast of Brazil, the Guayana Highlands and the Caribbean (McVaugh 1968). Although the family is considered well-delimited and © International Association of Wood Anatomists, 2013 DOI 10.1163/22941932-00000026 Published by Koninklijke Brill NV, Leiden Downloaded from Brill.com10/08/2021 06:52:18AM via free access 314 IAWA Journal 34 (3), 2013 easily recognizable in the field, the circumscription of its genera and species has been debated since the 19th century (Landrum & Kawasaki 1997; Lucas et al. 2005). One of the reasons for this confusion in generic boundaries is that many genera are distinguished by a single or relatively few, often cryptic characters, such as the degree of fusion in the calyx and in the embryo (Landrum & Kawasaki 1997; Salywon & Landrum 2007). Generic boundaries within Myrteae have attracted attention in past decades. Lucas et al. (2005, 2007) carried out molecular phylogenetic studies to clarify relationships within the tribe. They concluded that the traditional three subtribe system based on embryology and proposed by Berg (1855–56, 1857–59) is artificial, with subtribes Myr- ciinae and Eugeniinae being polyphyletic. The Plinia group is one of the well-supported monophyletic informal groups proposed by Lucas et al. (2007). It comprises four gen- era: Myrciaria, Neomitranthes, Plinia and Siphoneugena. Myrciaria O. Berg has 25 species (Govaerts et al. 2012) that occur from northern Argentina to Mexico and the Caribbean (Landrum & Kawasaki 1997). It is closely related to Plinia L., a genus dis- tributed from Brazil and Peru to the West Indies and Cuba (Barrie 2004). The distinc- tion between Myrciaria and Plinia is controversial, since only the persistence of the calyx in the fruit distinguishes them, which has led some authors (e.g. Legrand & Klein 1978) to consider Plinia species as Myrciaria. Plinia is considered artificial by some authors (e.g. Landrum & Kawasaki 1997); Barrie (2004) states that the range of the esti- mates of the number of species of Plinia (6–40 species) indicates its poor generic limits. Another indication is the controversial placement of species known as “jaboticabas”, a small group of eight species treated either as Myrciaria (e.g. Landrum & Kawasaki 1997) or Plinia (e.g. Govaerts et al. 2012). Those species will be treated here as Plinia. Neomitranthes Kausel ex D. Legrand comprises 14 species from the Brazilian Atlantic Domain (Souza 2009). It is closely related to Siphoneugena O.Berg, a small genus of 9 species ranging from southern Brazil to the Antilles (Sobral & Proença 2006). The distinction between them is also obscure, the principal difference being hypanthium morphology (circumscissile below the staminal ring in Siphoneugena and above in Neomitranthes) (Landrum & Kawasaki 1997). Due to these controversies about the generic limits within the Plinia group, the present study was undertaken to determine whether wood anatomical characters might be useful for distinguishing the genera. MATERIALS AND METHODS Wood samples of 19 species were obtained either from field expeditions or from various institutional wood collections, data on five species were obtained from the literature (Table 1). In the field, all samples were taken at breast height, either cut with a saw or sampled with an increment borer. Transverse, radial and tangential sections 20–25 µm thick were cut using a sliding microtome. Sections were bleached in 2–3% sodium hypochlorite, stained in 1% Astra blue and then in 1% safranin in 50% ethanol, dehydrated, and mounted in synthetic resin. Macerations were prepared using Frank- lin’s method, as modified by Kraus and Arduin (1997). Terminology, definitions and measurements follow recommendations of an IAWA Committee (1989). Measurements were taken using Image Pro-Plus 4.0. Downloaded from Brill.com10/08/2021 06:52:18AM via free access Santos et al. – Wood anatomy of selected Myrtaceae 315 Table 1. Specimens details. Genus / Species Registration number Specimen origin Myrciaria O. Berg M. disticha O. Berg RBw 8638 Linhares (ES), Brazil RBw 9022 Santa Teresa (ES), Brazil M. ferruginea O. Berg BOTw 854, BCTw 7939 Linhares (ES), Brazil M. floribunda(H. West ex Willd.) RBw 8598, RBw 8599, Quissamã (RJ), Brazil O. Berg RBw 8604 M. glazioviana (Kiaersk.) G.M. Barroso RBw 8755, RBw 8966, Rio de Janeiro (RJ), Brazil ex Sobral RBw 8989 M. guaquiea (Kiaersk.) Mattos & RBw 8754 Niterói (RJ), Brazil Legrand M. strigipes O. Berg BOTw 853 Linhares (ES), Brazil RBw 9024, RBw 9025 São Mateus (ES), Brazil Neomitranthes D. Legrand N. cordifolia (D. Legrand) D. Legrand RBw 8262 Sombrio (SC), Brazil N. glomerata (D. Legrand) D. Legrand RBw 8263 Palhoça (SC), Brazil N. obscura (DC.) N. Silveira RBw 8402 Rio de Janeiro (RJ), Brazil RBw 9023 Santa Teresa (ES), Brazil N. sp. (species unassigned) RBw 8639 Linhares (ES), Brazil Plinia Plum. ex L. P. cauliflora(Mart.) Kausel RBw 8751 Rio de Janeiro (RJ), Brazil P. costata Amsh. Tw 37774, Tw 37797 Nickerie, Suriname P. edulis (Vell.) Sobral RBw 8721, RBw 8749 Rio de Janeiro (RJ), Brazil P. ilhensis G.M. Barroso RBw 8753 Niterói (RJ), Brazil P. oblongata (Mattos) Mattos RBw 8981, RBw 8982 Santa Teresa (ES), Brazil P. peruviana (Poir.) Govaerts RBw 8722, RBw 8723 Rio de Janeiro (RJ), Brazil P. renatiana G.M. Barroso & RBw 9020, RBw 9021 Santa Teresa (ES), Brazil A. L. Peixoto BCTw 18482 Linhares (ES), Brazil Siphoneugena O. Berg S. kiaerskoviana (Burret) Kausel RBw 7307, RBw 7538 Nova Friburgo (RJ), Brazil S. reitzii D. Legrand RBw 8283 São Joaquim (SC), Brazil RESULTS We found that wood anatomy of the four genera is quite homogenous and so present a general description for them. Summaries of the qualitative and quantitative features that varied among species are in Tables 2 and 3, respectively. There is the possibility that some individual species can be recognized by their wood anatomy, but more samples need to be studied to verify this. Growth rings – Usually poorly marked, rarely absent, described as distinct in P. martinellii (Barros & Callado 1997) and P. rivularis (Santos 2012). Usually marked by radially-flattened, thick-walled fibers and lower frequency of axial parenchyma; some species also show lower frequency of vessels (Fig. 1A, D). Downloaded from Brill.com10/08/2021 06:52:18AM via free access 316 IAWA Journal 34 (3), 2013 Table 2. Summary of qualitative features that varied among Myrciaria, Neomitranthes, Plinia and Siphoneugena woods. Data are from direct observation, except when noted (1Santos 2012; 2Marchori & Muñiz 1987; 3Barros & Callado 1997; 4Paula et al. 2000). SVO = solitary vessel outline (A = angular, CO = circular to oval); DHV = deposits in heartwood vessels (C = common, O = occasional, A = absent/not observed); FWT = fiber wall thickness (T = thin to thick, VT = very thick); RMP = rays with multiseriate portions as wide as uniseriate portions (Y = yes, N = no); crystals (PC = in chambered axial parenchyma cells, E = crystals in enlarged axial parenchyma cells, T = two sizes of crystals in the same chambered cell, A = absent/not observed); vitreous silica (P = present in axial parenchyma cells; A = absent/not observed); * = unknown. Species Samples SVO DHV FWT Ray width RMP Crystals Vitreous silica M. cuspidata1 1 CO O T 1; 2 O A A M. disticha 2 CO C VT 1; 2 O T A M. ferruginea 2 CO O VT 1; 2 N A A M. floribunda 3 CO C T 1; 2–3 N A A M. glazioviana 3 CO A T 1; 2 N A A M. guaquiea 2 CO A VT 1; 2 N A A M.