Seed diversity in the Miconieae (Melastomataceae): morphological

Abstract

No part of this publication may be reproduced, stored, transmitted or disseminated, in any form, or by any means, without prior written permission from the publisher, to whom all requests to reproduce copyright material should be directed in writing.This authorization does not extend to any other kind of copying, by any means, in any form, and for any purpose other than private research use. AbstractThe seed morphology of 234 species distributed among 16 genera of the tribe Miconieae (Melastomataceae) was examined and documented with the use of scanning electron microscopy (SEM). Based on our observations and previously published investigations, we propose a set of 37 morphological characters for describing size, general shape, raphal zone, appendage, testa characters, and individual cell features of Miconieae seeds. Using these characters, we assembled detailed descriptions of all species in our sampling and constructed a data matrix for preliminary phenetic analysis (UPGMA algorithm; results to be presented elsewhere). In general, seed characters were easily identified and coded, although some of them presented difficulties, mostly due to the compression effects induced by fruit walls and neighboring seeds (e.g., shape). In contrast with other studies, we avoided the use of morphotypes, which have been shown to underutilize phenotypic variation. Our phenetic analysis does not agree with the traditional generic circumscription of the tribe, the sectional classification within Miconia, or with molecular phylogenetic analyses. This raises questions about the systematic and phylogenetic value of seed morphological characters in the tribe Miconieae. ResumenCon el uso del microscopio electrónico de barrido se examinó y documentó la morfología de las semillas de 234 especies, distribuidas en 16 géneros, de la tribu Miconieae (Melastomataceae). Con base en nuestras observaciones y apoyados en estudios previos, proponemos el uso de 37 caracteres morfológicos para describir el tamaño, la forma general, la zona rafal, el apéndice, los caracteres de la testa y las características de las células individuales de las semillas de Miconieae. Tales caracteres fueron utilizados para crear descripciones detalladas de todas las especies incluidas en nuestro muestreo y construimos una matriz de datos para efectuar un análisis fenético preliminar (algoritmo UPGMA). En términos generales, los caracteres de las semillas fueron identificados y codificados fácilmente, aunque algunos de ellos presentaron dificultades debido principalmente a los efectos de compresión inducidos por las paredes del fruto y las semillas adyacentes (p. ej., forma de la semilla). A diferencia de otros estudios, evitamos el uso de tipos morfológicos, ya que se ha demostrado que éstos subestiman la variación fenotípica. Nuestro análisis fenético no coincide con la circunscripción genérica tradicional de la tribu, ni con la clasificación seccional de Miconia, ni con los análisis filogenéticos moleculares. Estos resultados ponen en tela de juicio el valor siste...

Brasilianthus (Melastomataceae), a new monotypic genus endemic to ironstone outcrops in the Brazilian Amazon

“…Seed samples were sputter-coated at CAS with a mixture of gold-palladium and observed with a Zeiss/LEO 1450VP SEM (LEO, Cambridge, UK: Carl Zeiss SMT, Peabody, Massachusetts, USA), or sputter-coated with palladium at NY and studied with a JEOL-JSM 5410LV SEM (JEOL, Tokyo, Japan). For general macromorphological features and testa and individual cell characteristics of the seeds we adopted the terminology used by Ocampo & Almeda (2013) and references cited therein. Selected images were processed in Adobe Photoshop CS4 version 11.0 (Adobe Systems, San Jose, California, USA) to remove blemishes, background markings, and to enhance image quality.…”

Systematics of the Octopleura Clade of Miconia (Melastomataceae: Miconieae) in Tropical America

“…In other species like M. latidecurrens and M. palenquensis, the raphal zone is only expanded ventrally; in M. formicaria and M. spiciformis, this zone is not expanded at all. The seeds of the Octopleura clade do not have appendages like those described by Ocampo & Almeda (2013)-"a conspicuous, ventrally oriented extension of the seed corpus (with variable degree of inclination with respect to the raphal zone) located at the chalazal side, with size ≥ 20% the length of the seed", but some species may have a small protuberance at the chalazal end of the raphal zone. This protuberance is common in at least fifteen species of the Octopleura clade, including all species in the Variabilis subclade (Pl.…”

“…Seeds:-Although the phylogenetic significance of seed characters remains to be better understood, Ocampo & Almeda (2013) provide the most comprehensive account of seed diversity in the Miconieae to date, with a comprehensive descriptive terminology based on useful taxonomic characters and their variation (Fig. 6).…”

“…The hilum is a ridge formed by the portion of the funiculus (a continuation of the funicular vascular bundle) adnate to the anatropous seeds (Harris & Harris 2001, Ocampo & Almeda 2013, Sousa & Zárate 1988. In this sense the raphal zone comprises the raphe, the hilum, and the surrounding tissue on the ventral part of the seed, which has different cell morphological features than the corpus (Fig.…”

“…These characters constitute the morphological synapomorphies for this clade , Judd & Skean 1991. Indumentum and seed morphology are quite diverse in the clade, as is the case for the Melastomataceae de Jussieu (1789: 328) generally (Ocampo & Almeda 2013, Wurdack 1986). …”