BONPLANDIA 13(1-4): 21-29. 2004 SYSTEMATICS OF AMOMYRTUS (BURRET) D. LEGRAND & KAUSEL (MYRTACEAE) LESLIE R. LANDRUM1 & ANDREW SALYWON2 Summary: Landrum, L. R. & Salywon, A. 2004. Systematics of Amomyrtus (Burret) D. Legrand & Kausel (Myrtaceae). Bonplandia 13(1-4): 21-29. ISSN: 0524-0476. The systematics of Amomyrtus, an endemic genus of southwestern temperate South America, is reviewed. In molecular phylogenetic studies the genus is supported as monophyletic, with its closest relatives being other American genera such as Legrandia and Pimenta. A lectotype for Myrcia lechleriana Miquel is chosen. Key words: Taxonomy, Amomyrtus luma, Amomytus meli, South America. Resumen: Landrum, L. R. & Salywon, A. 2004. Sistemática de Amomyrtus (Burret) D. Legrand & Kausel (Myrtaceae). Bonplandia 13(1-4): 21-29. ISSN: 0524-0476. Se revisa la sistemática de Amomyrtus, un género endémico del sudoeste de América del Sur. En los estudios moleculares el género aparece como monofilético, siendo sus parientes más cercanos los géneros americanos Legrandia y Pimenta. Se elige un lectotipo para Myrcia lechleriana Miquel. Palabras clave: Taxonomía, Amomyrtus luma, Amomytus meli, Sudamérica. Amomyrtus (Burret) D. Legrand & Kausel relatively large (4-6 mm long), hard seeds, is a genus of two species endemic to the wet moderately to strongly aromatic leaves, and temperate forests of southern Chile and pentamerous flowers (Landrum 1988). adjacent Argentina. Both species are known Amomyrtus meli (Phil.) D. Legrand & Kausel for their hard wood and aromatic leaves. No and A. luma (Molina) D. Legrand & Kausel unique morphological synapomorphies distin• are both trees that reach a size of up to 20 m. guish the genus, but it can be distinguished Amomyrtus meli grows only in Chile from from other genera of Myrtaceae through a Arauco to Chiloe at elevations from sea level combination of characters of the embryo, seed to ca. 600 m; andA luma grows from near sea coat, flowers and inflorescence (McVaugh level to ca. 800 m from Maule to Aisen in 1968; Landrum 1988; Landrum and Sharp Chile and in the Andes of Argentina from 1989) and specifically from other genera of Neuquen to Chubut. The species commonly southern South America by a combination of grow near each other in their region of 1 School of Life Sciences, Arizona State University, P. O. Box 874501, Tempe, Arizona 85287-4501, USA 2 U. S. Department of Agriculture, Agricultural Research Service, U.S. Water Conservation Laboratory, Phoenix, Arizona, 85040-8807, USA 21 BONPLANDIA 13(1-4). 2004 overlap, but have slightly different habitats especially subtribe Myrtinae, are being as discussed below. No hybrids are known investigated using molecular phylogenetic even though the flowering periods overlap, analyses of sequence data from the nuclear suggesting some type reproductive isolating ribosomal DNA Internal Transcribed Spacer mechanism. Region (ITS) of both Old and New World The phylogenetic affinities of Amomyrtus fleshy fruited and capsular fruited genera are not clear but various kinds of evidence (Salywon, 2003; Salywon & al, 2004). In have become available in recent years. these studies, maximum parsimony, Bayesian Plants native to temperate South America analyses and neighbor-joining methods all often have relatives in Australasia (e.g., strongly support (100 % bootstrap support Nothofagus, Eucryphia, Laurelia, Gevuina, and 100% Bayesian posterior probability) the Tepualia) or temperate eastern South Ame• monophyly of Amomyrtus, which is not rica or the central or northern Andes (e.g., surprising for a group of two similar species, Myrceugenia, Blepharocalyx, Myrcianthes, but it is the first time that the monophyly of Azara, Escallonia) (Landrum 1981). One the genus has been tested using molecular might expect that relatives of Amomyrtus methods. In addition, the neighbor-joining would be found in one of those areas. trees, several of the most parsimonious trees, Secondary chemical data indicate that and highest likelihood Bayesian trees suggest Amomyrtus may have relatives in either that Amomyrtus has a sister group relationship area. Weyerstahl & al. (1992) found that with Legrandia, a morphologically distinct, Amomyrtus has certain 2-alkylchromones monotypic genus endemic to temperate Chile. otherwise unknown in plants and 1-pheny lalkan- In some analyses (i.e., neighbor-joining and 3-ones, only one of which (l-phenylhexan-3- Baysian majority rule) the Amomyrtus- one) had previously been found in Stellera Legrandia clade is sister to a clade of two chamaejasme L. (Gentianaceae). The latter Caribbean species of Pimenta, with the New compound was also found by Weyerstahl Zealand endemic Lophomyrtus and other & al. in Amomyrtella guili (Speg.) Kausel Australasian genera more distantly related. In (Myrtaceae), of northwestern Argentina. all of these analyses Lophomyrtus is resolved A similar 2-alkylchromone (2-isopropyl- as sister to Lenwebbia of Australia. The sister chromone) has been found in Lophomyrtus group relationship of these two Australasian bullata (Soland. Ex A. Cunn.) Burret genera is also supported by their quite similar (Myrtaceae) of New Zealand (Briggs and morphology (Snow & al. 2003). The higher White, 1971). The distribution of these level generic relationships of the fleshy- compounds is still of course poorly known, fruited genera in these phylogenetic analyses but if they prove to be unusual and restricted lack significant bootstrap support or clade to a few genera, then phylogenetic affinities credibility values and are thus largely between Amomyrtus, Amomyrtella and unresolved, due to short internodes between Lophomyrtus may be indicated. most genera. This condition is most likely due to an early rapid radiation of Myrtoideae. In Burret (1941) considered the species of any case molecular studies conducted so far Amomyrtus and Amomyrtella to be part of a seem to indicate an American origin for mainly Brazilian genus Pseudocaryophy- Amomyrtus and no detectable close relation• llus. All share a similar subapical protruding ship with any Australasian genera. More data placenta, which was probably the basis of from other segments of DNA and/or from Burret's placement. Recently Landrum more genera are needed for more robust (1986) submerged the type species of phylogenetic hypotheses. In particular, se• Pseudocaryophyllus in Pimenta, a mainly quence data from Amomyrtella would be Caribbean genus, but excluded Amomyrtus interesting as it is another American genus that and Amomyrtella. His reasons for excluding earlier studies (Burret 1941; Weyerstahl & al. the latter genera were differences in seed 1992) have indicated might be closely related coat, embryo and inflorescence structure. to Amomyrtus. Generic relationships of the Myrtaceae, 22 L.R. Landrum & A. Salywon, Systematics of Amomyrtus (Myrtaceae) Amomyrtw (Burret) D. Legrand & cm wide; calyx-lobes linear, linear oblong, or Kausel narrowly triangular; seed 4-4.5 mm long, grey-green; hypanthium 2-2.5 mm long, not Kausel, E, Lilloa 13: 145. ("1947") 1948. noticeably glandular; usually growing near Pseudocaryophyllus Berg, sect. Amomyrtus water. Burret, Notizb. Bot. Gart. Berlin-Dahlem 15: 1. A. luma 514. 1941. Type. Eugenia darwinii Hooker f, lectotype designated by McVaugh (Taxon 17: 403. T. Trunk more or less uniformly whitish; twigs 1968). obscurely pubescent to glabrous; leaves strongly aromatic, often over 3 cm long and 1.5 cm wide; Aromatic shrubs or trees up to ca. 20 m calyx-lobes approximately triangular, slightly high, with smooth or somewhat scaly bark; wider than long; seed ca. 5-6 mm long, light tan; hairs simple, unicellular; leaves opposite, hypanthium 2.5-3.5 mm long, strongly glandular; persistent, coriaceous, petiolate, usually lan• usually growing as an understory tree in upland ceolate or ovate; inflorescence a solitary habitats. flower or bracteate shoot of ca. 6 flowers, the 2. A. meli peduncles solitary (or rarely superimposed); flowers perfect, pentamerous; bracteoles caducous at or before anthesis; calyx lobes 1. Amomyrtus luma (Molina) D. Legrand & persistent; petals white; stamens whitish, 30- Kausel 80; anthers with 0-1 gland in the connective; Figs. 1A, D, E & F and 2B ovary 2-3- locular, the placentae attached to the upper septum, more or less shield-shaped, Kausel, E, Lilloa 13: 146. ("1947") 1948. the ovules radiating from the placental Myrtus luma Molina, Saggio sulla storia natu• margin; fruit a berry, the seeds hard, 1-4, rale del Chili, ed. 1. 173. 1782. Type. Description shaped like a flattened snail's shell with a of Molina. single coil, 4-6 mm long; embryo tinged Myrtus multiflora Jussieu ex Jaume Saint-Hillaire, purple, C-shaped, the hypocotyls about as in Duhamel, Traite arbr. arbust, ed. 2, 1: wide or slightly wider than the cotyledons, the 208. 1800-1803. Type. Chile. "Rapporte par cotyledons less than 1/5 as long as hypocotyl, Dombey. Herb, de Jussieu," Dombey s.n. membranous, folded back against the hypoco- (holotype, P, ex herb. Jussieu, = MICH neg. 1967!; tyl. F neg. 7924 of apparent isotype at G!). Amomyrtus is distinguished from all other Eugenia darwinii Hook, f, Fl. Antarctica genera of southern South American Myrtaceae 277. 1846. Type. "South Chili, Cape Tres Mün• by its pentamerous flowers, hard seeds 4-6 tes," Darwin s.n. (lectoype CGE, designated by mm long, and moderately to strongly aromatic Porter [1986]; isolectotype, K!, = ASU photo!). leaves. Burret's name for this group appears to Myrtus darwinii (Hook, f.) Barneoud, in Gay, be a union of the names Amomis Berg (= Fl.