Leslie R. Landrum

The genera of Myrtaceae in Brazil: an illustrated synoptic treatment and identification keys

A synoptic treatment of the 23 genera of Myrtaceae in Brazil and keys for their identification are provided, including a general key to all genera, a key to the subtribes, and keys to the genera of each subtribe. Four commonly recognized genera that we consider to be of uncertain status are provisionally treated as segregates of large related genera: Marlierea and Gomidesia with Myrcia; and Hexachlamys and Calycorectes with Eugenia. Important characters of the inflorescence, calyx, ovary, placenta, ovule, fruit, seed, and embryo are discussed and illustrated. Information provided for each genus includes concise descriptions, geographic distribution, approximate number of species, and comparisons to related genera. Families that might be confused with Myrtaceae are briefly discussed. A new combination, Mosiera prismatica (D. Legrand) Landrum, is made.

A SIMPLE TEST FOR THE POSSIBLE SIMULTANEOUS EVOLUTIONARY DIVERGENCE OF TWO AMINO ACID POSITIONS

Summary A taxonomic character for a group of organisms under study is said to be divergent or uniquely derived for that group if, during the evolution of that group, each character state arose only once. Homologous amino acid positions in homologous proteins can be thought of as taxonomic characters whose states are amino acids. In a similar way, DNA nucleotide positions can also be considered taxonomic characters. In the exposition below, we describe a simple test to determine when it is not possible for two amino acid (or nucleotide) positions to be divergent at the same time.

Volatile Leaf Oils of Caribbean Myrtaceae. I. Three Varieties of Pimenta racemosa (Miller) J. Moore of the Dominican Republic and the Commercial Bay Oil

ABSTRACT The foliar essential oils of Pimenta racemosa (Miller) J. Moore var. grisea (Kiaerskov) Fosb. are dominated by geraniol (0–85.52%), methyl eugenol (0.30–92.60%), and/or trans-methyl isoeugenol (0–86.32%). The foliar essential oils of Pimenta racemosa var. hispaniolensis (Urban) Landrum are dominated by 1,8-cineole (0.05–37.96%), methyl chavicol (0–22.61%), methyl eugenol (0–63.88%), γ-terpinene (0–16.67%), terpinen-4-ol (0.08–28.98%), and/or thymol (0–44.02%). The foliar essential oils of Pimenta racemosa var. ozua (Urban & E. Ekman) Landrum are dominated by 1,8-cineole (47.24–55.93%), limonene (3.62–30.07%), and/or α-terpineol (6.68–15.12%). The commercial bay oil (P. racemosa var. racemosa) is dominated by chavicol (<0.01–15.51%), eugenol (44.41–68.93%), methyl eugenol (0–11.88%), and/or myrcene (0.10–16.17%).

Phylogenetic relationships in Myrceugenia (Myrtaceae) based on plastid and nuclear DNA sequences

Graphical abstract Highlights ► Phylogenetic relationships are reconstructed within Myrceugenia. ► Genus Myrceugenia is monophyletic only when M. fernandeziana is excluded. ► Chilean and Brazilian species are two separate lineages. ► Brazilian species are included in a derived monophyletic group.

Volatile leaf oils of American Myrtaceae. III. Psidium cattleianum Sabine, P. friedrichsthalianum (Berg) Niedenzu, P. guajava L., P. guineense Sw., and P. sartorianum (Berg) Niedenzu

ABSTRACT Samples of five species of the genus of Psidium (Myrtaceae) are analyzed for essential oils. The foliar oil of P. cattleianum Sabine is dominated by β-caryophyllene (59.92±1.70%). The foliar oil of P. friedrichsthalianum (Berg) Niedenzu is dominated by β-caryophyllene (36.82±19.44%) and α-pinene (10.61±13.70%). The foliar oil of P. guajava L. is dominated by β-bisabolene (19.21±2.44%) and β-sesquiphellandrene (14.75±0.01%). The foliar oil of P. guineense Sw. is dominated by β-bisabolene (13.18±2.00%) and α-pinene (12.85±5.42%). The foliar oil of P. sartorianum (Berg) Niedenzu is dominated by α-pinene (16.66±1.05%), β-caryophyllene (12.35±2.82%) and α-phellandrene (9.81±1.13%).

Seed Coat Characters of Some American Myrtinae (Myrtaceae): Psidium and Related Genera

Psidium (Myrtaceae: Myrtinae) has long been one of the most difficult genera of American Myrtaceae to define. We here describe and illustrate, with SEM photographs, four char- acteristics of seed coats that help to distinguish Psidium from its American relatives: 1) seed coat surface dull or rough with an external layer of pulpy tissue; 2) hard portion of outer seed coat usually 8-30 cells thick at narrowest point; 3) prevalent shape of cells in the outer seed coat elongate; and 4) lumen of cells in the outer seed coat tending to be less than 1/2 as wide as the cell. Recognition of these characters allows extraction of certain anomalous groups from Psidium.

Volatile leaf oil of Calycolpus australis Landrum (Myrtaceae).

Abstract The essential oil of the leaves and stems of Calycolpus australis, collected in Minas Gerais, Brazil and examined by GC/MS, is dominated by γ-terpinene (14.07±2.92%), terpinen-4-ol (13.11±1.03%), linalool (12.52±0.91%) and α-terpinene (11.53±1.93%).

What has Happened to Descriptive Systematics? What Would Make it Thrive?

Abstract No abstract available. Communicating Editor: Richard Jensen

Variability of Embryos in Subtribe Myrtinae (Myrtaceae)

Embryos are quite variable in subtribe Myrtinae (Myrtaceae). Observations of anat- omy and germination indicate that differences are mainly due to degrees of swelling of the hy- pocotyl. Swollen hypocotyls have enlarged cells filled with starch. Misinterpretation of embryo structure of genera with swollen hypocotyls has led previous workers to recognize formal taxo- nomic entities that we do not accept. Xanthomyrtus Diels, which has been assigned to Myrtinae (subfam. Myrtoideae), has an embryo unlike any other in the subtribe. It seems to be most similar to genera of Leptospermoideae. It is hypothesized that the three predominant embryo structures in Myrteae are derived from a small ancestral embryo and are independent adaptations for increas- ing the amount of stored food in the embryo. Marlieriopsis eggersii Kiaerskou is transferred to Blepharocalyx Berg.

Volatile Leaf Oils of Caribbean Myrtaceae. II. Pimenta dioica (L.) Merr. of Jamaica

ABSTRACT Two oils produced by steam distillation of the leaves of Pimenta dioica (L.) Merr. of Jamaican origin were examined by GC/MS and found to be rich in eugenol (66.38–79.24%).