Aiouea

Abstract: A survey of the diversity, distribution, and conservation status of the family Lauraceae in southern Mexico was conducted. The diversity account resulted in a list of 120 species representing 10 genera: Aiouea, Beilschmiedia, Cassytha, Cinnamomum, Licaria, Litsea, Mocinnodaphne, Nectandra, Ocotea and Persea. The states of Chiapas, Oaxaca, and Veracruz have the largest numbers of species, particularly for the cloud forest and the tropical rain forest. Endemic species account for 47.5% of the surveyed taxa, which concentrate in Chiapas, Oaxaca, and Veracruz. Only 58 of the species considered in the study are present in the system of nature reserves in southern Mexico. The general implications of these findings for the persistence of this component of the Mexican flora are discussed.

Abstract: Cuticular characters are epidermal or stomatal characters and are often used in the taxonomy and classification of fossil or extant Lauraceae. However, there is no consensus on their usefulness, especially as to which characters take priority and at which taxonomic level. This study compared the cuticular characters of species within the Neotropical genera of the Ocotea Aubl. complex to the reported molecular phylogeny. Species of the following genera are included in this study: Aiouea Aubl., Aniba Aubl., Dicypellium Nees & Mart., Endlicheria Nees, Kubitzkia van der Werff, Licaria Aubl., Nectandra Rol. ex Rottb., Ocotea, Paraia Rohwer, H. G. Richt. & van der Werff, Pleurothyrium Nees, Rhodostemonodaphne Rohwer & Kubitzki, Umbellularia (Nees) Nutt., and Urbanodendron Mez. Species groups based on cuticular characters, especially characters of the stomata, agreed well with the various clades in the molecular phylogeny, but did not agree with species grouped according to the traditional generic conce...

Abstract: The genus Sextonia is described; it consists of two species, the rather widespread S. rubra and the new species S. pubescens, restricted to eastern Peru. Ocotea is the largest genus of neotropical Lauraceae, including at least 300 species (van der Werff, 1991). It is not surprising that with such a large number of species the genus shows considerable morphological variation, is difficult to delimit, and is in much need of a modern revision. Oftentimes the genus has been used to accommodate species that could not be adequately placed in other, better defined genera. As information from other disciplines, most notably wood and bark anatomy (Richter, 1981), has become available, some of the anomalous species have been removed from Ocotea and recognized as distinct genera. Rohwer et al. (1991) created the genus Chlorocardium for two species previously placed in Ocotea and discussed some other problematical species. I propose to recognize one of those species, until now treated as Ocotea rubra, as belonging to a distinct genus and will describe a new species of this genus as well. Sextonia van der Werff, gen. nov. TYPE: Sextonia rubra (Mez) van der Werff. Figure 1. Arbores magnae. Folia ad apices ramulorum aggregata. Inflorescentiae axillares, racemosae vel paniculatae. Tepala 6, inaequalia, 3 exteriora quam 3 interiora minora, erecta; stamina 9, 4-locellata, 6 exteriora locellis in arcu non profundo dispositis, 3 interiora locellis in 2 paribus superpositis; staminodia 3; receptaculum profundum. Fructus cupula insidens, ab ea 13 vel fere omnino obtecta. Large trees, to 45 m tall. Twigs thick, corky, terete. Leaves alternate, clustered near the tips of the branches, pinnately veined, without domatia. Inflorescences axillary, racemose or paniculate, ultimate divisions of inflorescences frequently not strictly cymose, but racemose. Tepals erect, unequal, the outer three smaller than the inner three; stamens 9, 4-celled, the outer 6 with the cells in a shallow arc, the inner 3 with the cells placed in two pairs, the filaments short, as wide as the anthers, staminodia 3; receptacle deep. Fruit initially enclosed in the cupule, at maturity either 2/ exserted or almost completely enclosed in the cupule. The new genus Sextonia is readily recognized by having clustered leaves and flowers with unequal tepals, characters already mentioned by Rohwer et al. (1991). The differences in wood and bark anatomy between Ocotea and Sextonia (as O. rubra) were amply discussed by Richter (1981), and indeed the main reason that Rohwer et al. (1991) did not describe a new genus to accommodate O. rubra was their reluctance to describe another monotypic genus. In a genus as large as Ocotea it is not surprising to find individual species or groups of species that differ in one or more morphological characters from the rest of the species, and finding such differences is not a sufficiently strong argument for describing a new genus. However, when such morphological differences are supported by differences in wood and bark anatomy the argument for a new genus is stronger. Three reasons made me consider the generic status of 0. rubra again. The first is the recent discovery of an undescribed species closely related to O. rubra, sharing with it the clustered leaves and flowers with unequal tepals, but differing in having pubescent flowers and racemose inflorescences. This new species has wood and bark anatomy similar to O. rubra. Describing this species in Ocotea would clearly be incorrect. The second argument is that during a study of the embryology of Lauraceae (Heo et al., in prep.) Ocotea rubra was found to differ clearly from the other four investigated species of Ocotea in having the mature embryo sac protruding from the nucellus, a character state otherwise only found in Beilschmiedia, Caryodaphnopsis, Cryptocarya, Endiandra, and Potameia, but lacking in genera considered closely related to Ocotea, such as Aiouea, Aniba, Cinnamomum, Licaria, Mezilaurus, and Nectandra. The third is that the inflorescences of the two species of Sextonia are different from those found in Ocotea. In Ocotea the flowers are arranged in cymes, with the lateral flowers of a cyme strictly opposite. In Sextonia rubra, however, the flowers are not arranged in cymes. Frequently the ultimate branching of the inflorescences appears racemose and flowers are not strictly opposite. The inflorescence types of Lauraceae and their importance for the suprageneric classification are discussed in detail by van NovoN 7: 436-439. 1997. This content downloaded from 157.55.39.151 on Thu, 07 Jul 2016 05:31:01 UTC All use subject to http://about.jstor.org/terms Volume 7, Number 4 van der Werff 437 1997 New Genus of Lauraceae

Abstract: H.M.G. — Herb. Museu Goeldi, Para H.R.J. = Herb. Inst. Biol. Veget. (Rio de Janeiro) J. = Herb. Jussieu, Paris K. = Kjobnhavn Ki. = Kiel (Germany) Kw. = Kew L. = Leiden Lg. = Leningrad Lam. — Herb. Lamarck tParis) Lp. — Leipzig M. = Miinchen Mi. = Missouri Bot. Garden Mn. = Herb. Museu Nacional (Rio de Janeiro) Ms. = Meissner herb. (New York) NY. = New York O. = Fielding herb. (Oxford) P. = Paris R. ;= Jardim Botanico, Rio de Janeiro St. : Stockholm U. = Utrecht W. = Wien