Ovules and seeds in Acalyphoideae (Euphorbiaceae): structure and systematic implications

Acalyphoideae, the largest subfamily of Euphorbiaceae, are investigated with respect to ovule and seed structure on the basis of 172 species of 80 genera in all 20 tribes of Acalyphoideae sensu Webster. All species of Acalyphoideae examined have bitegmic ovules with a non-vascularized inner integument. However, noticeable differences exist among and sometimes within the genera in the thickness of the inner and outer integument, the presence or absence of vascular bundles in the outer integument, whether ovules are pachychalazal or not, the presence or absence of an aril, seed coat structure (in terms of the best-developed mechanical cell-layer), and the shape of cells constituting the exotegmen. For the latter two characters, two different types of seed coat (i.e., "exotegmic" and "exotestal") and three different types of exotegmic cell (i.e., palisadal, tracheoidal and ribbon-like) were distinguished. Comparisons showed that three tribes Clutieae, Chaetocarpeae and Pereae are distinct from the other Acalyphoideae as well as from the other Euphorbiaceae in having an exotestal seed coat with a tracheoidal exotegmen. The tribe Dicoelieae is also distinct from the other Acalyphoideae in having an exotegmic seed that is composed of ribbon-like cells of exotegmen (i.e., cells both longitudinally and radially elongated, sclerotic and pitted). The tribe Galearieae, which should be treated as a distinct family Pandaceae, is also distinct from the other Acalyphoideae in having an exotegmic seed with a tracheoidal exotegmen (i.e., cells longitudinally elongated, sclerotic and pitted). The remaining genera of Acalyphoideae always have an exotegmic seed with a palisadal exotegmen (i.e., cells radially elongated, sclerotic and pitted). The shared palisadal exotegmen supports the close affinity of Acalyphoideae (excluding five tribes) with Crotonoideae and Euphorbioideae. Within the remaining genera of Acalyphoideae, a significant diversity is found in ovule and seed morphology with respect to the thickness of the inner and outer integument, the size of chalaza, vascularization of an outer integument and an aril.     

Le pollen de la tribu des Acalypheae (Acalyphoideae,Euphorbiaceae)

Le pollen de 2/730 genres et de 48/1300 espèces de la tribu des Acalypheae a été étudié en microscopie photonique et électronique à balayage. Les variations des caractères aperturaux et de la disposition des éléments ornementaux permettent de caractériser les onze sous-tribus. Le pollen est généralement colporé et présente presque toujours de petits épaississements de la nexine autour des apertures. Seuls deux genres font exception, Sampantaea p.p. et Dysopsis dont le pollen présente généralement trois simples sillons ectoaperturaux très étroits. Le tectum est perforé et porte en principe des microépines ou microverrues autour des perforations à l'exception de quelques rares espèces où l'ornementation est striée (Micrococca scariosa, Homonoia jaranensis) ou réticulée (Amyrea, Mareya longifolia, Seidelia). Le pollen des Acalypheae se répartit dans deux grands types: 1° le tectum est largement perforé et les grains sont en général plutôt longiaxes; 2° le tectum est à peine microperforé et les grains sont le plus souvent plutôt bréviaxes. Les variations des caractères du pollen: diminution des perforations tectales, réduction considérable de l'ectoaperture et/ou, de l'endoaperture qui peut disparaître même, sont corrélatives de celles de la fleur et du type de pollinisation. Le pollen des Acalypheae présente des rapports évidents avec celui des 3 tribus voisines appartenant aux Acalyphoideae, tandis que ses ressemblances avec celui des Crotonoideae et des Phyllanthoideae ne sont liées qu'à la disposition des éléments libres sur l'exine.

The pollen of 27/30 genera and 48/1300 species of the tribe Acalypheae have been studied by means of L.M. and S.E.M. Variations in the character of the apertures and in the sculpturing elements allow a characterization into eleven subtribes. The pollen is generally colporate and mostly has small nexine thickenings around the apertures. The genera Sampantaea and Dysopsis are the only exceptions to this having pollen with three very narrow ectoapertural simple furrows. The tectum is perforate and has microspines or micropapillae around the perforations, with the exception of some rare species in which the sculpturing is striate (Micrococca scariosa, Homonoia javanensis) or reticulate (Amyrea, Mareya longifolia, Seidelia). The pollen of the Acalypheae belong to two great types: 1° the tectum is widely perforate and the grains are generally longiaxe; 2° the tectum is scarcely microperforate and the grains are often breviaxe. The variations in the pollen characters: a decrease in the tectal perforations, and a great reduction in the ectoaperture and/or the endoaperture which can even disappear, are correlative with those of the flower and its type of pollination. The pollen of the Acalypheae clearly resembles that of the three nearest tribes of the Acalyphoideae. Similarities with the Crotonoideae and the Phyllanthoideae are evident except for the placement of the free elements on the exine.     

Pollen morphology of the Acalyphoideae and Euphorbioideae (Euphorbiaceae) of the Caatinga ecoregion in Brazil

This study dealt with six species of Acalyphoideae and 18 species of Euphorbioideae occurring in the Caatinga ecoregion, with emphasis on endemic species. Pollen samples were obtained from herbarium specimens and were acetolysed and analysed via light and scanning electron microscopy. The pollen of three genera of Acalyphoideae was medium to large, 3-colporate or 3-colpate, with an echinate-perforate exine that was reticulate, bireticulate, and microreticulate. The six genera of Euphorbioideae studied exhibited pollen grains that were small, medium and large; 3-colporate with margines; and an exine with microreticulate, microreticulate-rugulate, microreticulate-caveate, and reticulate ornamentation. The pollen characteristics were more variable in the Acalyphoideae compared to the relatively homogeneous Euphorbioideae. This study provides new data and interpretations of the pollen morphology of two subfamilies of the Euphorbiaceae of the Caatinga ecoregion in Brazil.     

A Revision of Chinese Phyllanthus (Euphorbiaceae)

The present paper is the outcome of a taxonomic study of Chinese Phyllanthus plants in our flora. Phyllanthus is one of the largest genera in Euphorbiaceae, and is distributed in whole China except for the northwest, extending from 92° to 124° E and 18° to 41°N. It includes 6 subgenera, 7 sections, 33 species and 4 varieties, of which 1 subgenus and 5 species are described as new, and 1 new name and 9 synonyms are proposed.     

Notes on neotropical Amanoa (Euphorbiaceae)

Lectotypes are designated forAmanoa caribaea Krug & Urban andA. guianensis Aublet; presumed syntypes of the latter taxon are shown to be heterogeneous by inclusion of a previously unrecognized species. Four new species ofAmanoa are described:A. congesta from French Guiana and northeastern Brazil;A. gracillima from Manaus, Brazil;A. nanayensis from Amazonian Peru and adjacent Colombia and Brazil; andA neglecta from French Guiana and Surinam.Amanoa sinuosa is proposed as a new name for the later homonymA. robusta Leal. A key to the 13 neotropical species is presented.     

Foliar architecture and anatomy of <Emphasis Type="Italic">Bernardia</Emphasis> and other genera of Acalyphoideae (Euphorbiaceae)

A comparative study of leaf architecture and anatomy of 42 species of Bernardia and other genera related of Acalyphoideae was undertaken to identify characters that support infrageneric and specific delimitation. Thirty variable foliar architectural and anatomical characters were studied. Some characters are consistent (e.g., venation pattern, secondary and tertiary vein arrangement, presence or absence of agrophic veins, type of areoles, bundle sheath cell type, presence or absence of fibers in the mesophyll, trichome type, stomata location, and type of crystals), and characterize genera. In addition, foliar character distribution within Bernardia supports the most recent infrageneric classification.     

A revision of Ptychopyxis (Euphorbiaceae) in southeast Asia

Ptychopyxis is a genus comprised of 11 species. Nine are found in southeast Asia mainland and west Malesia and two species are endemic to New Guinea. One of the endemic New Guinean species is newly described here, viz. P. esdras Stoops sp. nov.     

A Phylogenetic Study of Tribe Euphorbieae (Euphorbiaceae)

A phylogenetic investigation of a monophyletic lineage of spurge plants, tribe Euphorbieae, was conducted to elucidate evolutionary relationships, to clarify biogeographic patterns, and to reexamine the previous classification of Euphorbieae. Cladistic analyses of the 52 morphological characters of 61 species resulted in 2922 equally most parsimonious trees of 193 steps with a consistency index of 0.34. The strict consensus tree indicates genus Anthostema of subtribe Anthosteminae as a likely sister group to all other members of tribe Euphorbieae. The morphological data support a monophyletic origin of subtribe Euphorbiinae, but the subtribes Anthosteminae and Neoquillauminiinae did not form monophyletic groups. Although the previous taxonomic treatments within tribe Euphorbieae have supported the generic status of Pedilanthus, Monadenium, Synadenium, Chamaesyce, and Elaeophorbia, the results of this analysis do not support generic placement of them based on cladistic principles. Recognition of these groups as genera results in Euphorbia becoming a paraphyletic group. One solution to this problem in Euphorbieae is to divide the largest genus Euphorbia into several monophyletic genera and to keep the generic ranks for previously recognized genera. The distribution of basal endemic genera in Euphorbieae showed African and east Gondwanan affinities and strongly indicated that the ancestor of Euphorbieae originated prior to the breakup of Gondwanaland from an old group in Euphorbiaceae. However, some recent African taxa of Euphorbia should be interpreted by transoceanic dispersal from the New World ancestors.     

Functional andromonoecy in Euphorbia (Euphorbiaceae)

The occurrence of cyathia containing staminate flowers but lacking a pistillate flower was studied in 17 species of Euphorbia. Male cyathia were found in the majority of species studied (88.2%) giving functional andromonoecy. In the male cyathia, the pistillate flower is generally totally absent, but sometimes a vestigial pistillate flower with a non-functional ovary is present. The proportion of male cyathia varied at both the population and species level. The position of male cyathia within the inflorescence showed a constant pattern among species: the proportion of male cyathia decreased from the first to the last levels of the pleiochasia. In general, perennial species had significantly higher proportions of male cyathia than annual species (mean 20 and 2.3%, respectively). In annual species there was a trend for production of male cyathia only in the first level of the inflorescence, whereas in perennials production up to the fourth level of the inflorescence was usual. Functional andromonoecy is common in Euphorbia and represents a new sex segregation in the genus. The selective forces causing this secondary sex segregation in Euphorbia, such as improved pollination or increased outcrossing, are discussed.     

A new species of Croton (Euphorbiaceae) widespread in Mexico

Croton rzedowskii is described, the type being from San Luis Potosí. The species ranges from San Luis Potosi westward to Zacatecas, thence southeastward to Oaxaca.     

A new species of <Emphasis Type="Italic">Acalypha</Emphasis> (Euphorbiaceae: Acalyphoideae: Acalypheae) from Belize and adjacent Mexico and Guatemala

Acalypha gentlei is described, illustrated and mapped. The species is endemic to Belize and adjacent areas of Mexico and Guatemala and restricted to semi-deciduous moist forests on limestone. The species is referred to Acalypha subgenus Linostachys.

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Resumen  Se describe, ilustra y grafica la distribución de Acalypha gentlei. Esta especie nueva es endémica a Belice y áreas adyacentes de México y Guatemala, y está restringida a bosques húmedos semi-deciduos sobre caliza. La especie es referida a Acalypha subgénero Linostachys.

     

A new species of Phyllanthus (Euphorbiaceae) from Somalia

Phyllanthus lunifolius sp. nov., a completely prostrate dwarf shrub from limestone rocks in the coastal part of central Somalia, is described and illustrated.     

湖南野桐属一新种

本种近似小果野桐M.microc arpus Pax et Hoffm.,区别在于：叶卵形或长圆状卵形,羽状叶脉,基部楔形,下延,两面密被星状绒毛。     

A new arborescent Euphorbia (Euphorbiaceae) from northern Somalia

Euphorbia spissa, sp. nov., a tree known from a single population on a rocky limestone slope in northern Somalia, is described and illustrated. The species is compared with the widespread E. tirucalli, as well as with E. cameronii and E. bariensis (endemics in Somalia), E. arbuscula (endemic on Socotra), and E. uzmuk (endemic in northern Yemen).