Raul Pozner

Instituto de Botánica Darwinion

Tillandsia subgenera Diaphoranthema and Phytarrhiza s.s. are closely related epiphytic and epilithic plants adapted to xeric habitats in the Americas. Several studies suggested that subgenus Diaphoranthema and the xerophytic species of subgenus Phytarrhiza should not be segregated into different subgenera. In recent phylogenetic analyses of Tilland...

• Background and aims. Atripliceae evolved and diversified by dispersals and radiations across continents on both hemispheres, colonizing similar semi-arid, saline-alkaline environments throughout the world. Meanwhile, its species developed different life forms, photosynthetic pathways, mono- or dioecy, and different morphological features in flowe...

Familia monotípica exclusiva de la Argentina.

With ca. 300 species of herbs, shrubs and subshrubs adapted to saline or alkaline soils, the evolution of the genus Atriplex is key to understand the development of semi‐arid environments worldwide. Previous phylogenetic analyses of Atriplex, including only a few species from South America, especially in comparison with North American species repre...

Congruence among different sources of data is highly desirable in phylogenetic analyses. However, plastid and nuclear DNA may record different evolutionary processes such that incongruence among results from these sources can help unravel complex evolutionary histories. That is the case of Nassauvia subgenus Strongyloma (Asteraceae), a taxon with f...

The Calyceraceae (47 spp.) is a small family of plants that is sister to the Asteraceae (∼ 25,000 spp.), one of the largest families of angiosperms. Most members of Calyceraceae are endemic to the Andes and Patagonia, representing an excellent model within which to study diversification patterns in these regions. The single phylogenetic study of Ca...

This contribution reviews all 51 names (45 species and six varieties) published in Apodanthera, recognizing 23 species (one of them with two varieties), a doubtful taxon (A. longipedicellata), and seven excluded taxa (five of them excluded by former authors, and two in this work: A. congestiflora y A. trifoliata). Thirteen new synonyms are here pro...

Calyceraceae is a small family with six traditionally recognized genera and 47 species from southern South America. Most species grow along the Andes (of both Argentina and Chile) and in arid regions of the Patagonian steppe. This family belongs to the well-supported MGCA clade within Asterales, which includes Menyanthaceae + Goodeniaceae + Calycer...

This is the first integrative synopsis of the genus Atriplex L. for South America, based on the study of compared external morphology of extensive collections from South American herbaria, type material, digital images, original publications and field observations. The South American Atriplex flora includes 55 species, 45 of which are native specie...

We describe and illustrate Mastigostyla coronata, a new species of Iridaceae from the high Andes of Jujuy (Argentina), morphologically similar to Mastigostyla vargasii. The inclusion of this new species in Mastigostyla is supported by a phylogenetic analysis based on plastid markers. We also present a morphological comparison among the sub-acaulesc...

Abstract— Valeriana serratifolia , a new species from the Andean region of northwestern Argentina, is described and illustrated. It can be distinguished from its closest morphological taxon, V. macrorhiza, by its entire, spathulate leaves with serrulate margin, and falcate fruits, 2‐2.5 mm long, crowned by the reduced annular calyx shifted toward t...

We describe a new species of Sicydium endemic to Argentina. Relationships and differences with morphologically and geographically closest species are discussed, including a key for material with staminate flowers to all species of Sicydium, and an illustration of the new species.

Abstract— This taxonomic treatment is the first in the genus Calycera based on a detailed study of morphology and a critical analysis of species boundaries. In this revision, nine species and four varieties are recognized, one new combination ( C. crassifolia var. spinulosa ), nine new synonymies (Anomocarpus axillaris, Boopis integrifolia, Calyc...

The Patagonian steppe is an immense, cold, arid region, yet phylogeographical-ly understudied. Nassauvia subgen. Strongyloma is a characteristic element of the steppe, exhibiting a continuum of morphological variation. This taxon pro-vides a relevant phylogeographical model not only to understand how past environmental changes shaped the genetic st...

Tillandsia subgenus Diaphoranthema (Tillandsioideae, Bromeliaceae) includes 29 epiphytic species distributed widely from southern North America to central Argentina and Chile. The species of Diaphoranthema are characterized by few small flowers, and most species are differentiated by phyllotaxy, leaf shape, flower number, and by the morphology and...

Morphological variation among the five species of Nassauvia subgenus Strongyloma was assessed through statistical analyses of morphometric traits in populations throughout the southern Andean-Patagonian region. Uni-and multivariate analyses were used to identify patterns of morphological variation in relation to geography. Additionally, species dis...

Renealmia elianae (Zingiberaceae), a new species from the Central Andes of Colombia is described and illustrated. Renealmia elianae is morphologically close to R. puberula, differing by the inflorescence position, corolla size, labellum texture, surface and color, and size of the epigynous glands.

A new apetalous species of Minuartia from the high Andes of northwestern Argentina, M. altoandina, is here described and illustrated. At first sight, M. altoandina is morphologically very similar to the European M. sedoides because of the absence of petals and ciliate leaf margin with narrow hyaline teeth; however, from a biogeographical point of v...

Amphitropical disjunct distributions between western North America and western South America have intrigued botanists for over a century. Here, specific examples of migration and speciation are investigated using herbaceous species from the phlox family (Polemoniaceae) as a model for considering the timing of dispersal relative to speciation. Compa...

Premise of the study: The understanding of homoplasic structures becomes more relevant when they are complex and define large angiosperm taxa. Inflorescence architecture usually fulfills both features, as happens with Cyperus, a genus with two taxonomical subdivisions characterized either by alternative expressions of Kranz anatomy (C(3) or C(4))...

Aim An integrative study of the endemic, yet ubiquitous, Patagonian shrub Mulinum spinosum (Apiaceae) was performed: (1) to assess the historical processes that influenced its geographical pattern of genetic variation; (2) to test hypotheses of its survival in situ or in glacial refugia during glacial cycles; and (3) to model its extant and palaeoc...

The Abildgaardieae tribe within the family Cyperaceae comprises six or seven genera, among which Abildgaardia, Bulbostylis and Fimbristylis pose a challenge regarding their morphological delimitation. Molecular phylogenetic analyses including species of Abildgaardieae are rare, but in most of those studies, Abildgaardia and Fimbristylis appear as m...

Premise of the study: Phylogenies based on molecular data are revealing that generalizations about complex morphological structures often obscure variation and developmental patterns important for understanding the evolution of forms, as is the case for inflorescence morphology within the well-supported MGCA clade (Menyanthaceae + Goodeniaceae + C...

Phylogeographical inferences, applied in a comparative framework across multiple species at a regional scale, provide the means for detecting regional and landscape-level patterns of biodiversity, which are important for understanding macroecology and evolution in a geographical mosaic against a backdrop broadly impacted by geological events. Altho...

We describe and illustrate two new species of Boopis from Argentina: Boopis pterocalyx (Mendoza province) and Boopis necronensis (Catamarca and La Rioja provinces). Both species are easily distinguished from the remaining species of Boopis (sensu lato, including Nastanthus) by the foliose, imbricate sepals, which become foliose and orbicular in the...

The nomenclatural revision of 51 names previously published, combined or synonymyzed under the genus Nastanthus (Calyceraceae) is presented. Six species are recognized with correct names and new synonyms established. The nomenclature of Nastanthus ventosus, Nastanthus scapigerus and Nastanthus compactus is updated, giving a total of 45 synonyms. Le...

De Gennaro, D., R. Pozner & O. Morrone (2010). Foliar anatomy of Sacciolepsis Nash (Poaceae). Candollea 65: 197–210. In Spanish, English and French abstracts. Leaf anatomy study of the genus Sacciolepis Nash (Poaceae, Panicoideae, Paniceae) is presented and discussed. It is based on the analysis of epidermis in paradermal view and blade sections of...

Spikelet structure and grouping are key characters to identify grasses. Here we tested the possibility that spikelet pairs, a distinctive morphological structure of many Andropogoneae and Paniceae, are the starting point for a secondary single spikelet condition that can also explain the change of spikelet orientation among Paniceae genera. As a fi...

We investigated changes in floral developmental patterns and sex determination in the PCK (phosphoenolpyruvate carboxykinase) clade using a comparative approach and SEM. We identified variation in patterns of floral development that may be correlated with sex determination. Nine different patterns of floret development were identified, based on sex...

Estudios moleculares recientes sugieren que Senecio sect. Senecio ser. Otopteri debería ser removido de Senecio para que este género extenso y taxonómicamente complicado sea monofilético. Con el propósito de evaluar la posición taxonómica de Senecio otites y la ubicación de la serie Otopteri, 13 especies, incluyendo S. otites, fueron examinadas en...

In grasses, inflorescence diversification and its correlation with species evolution are intriguing and not well understood. Part of this problem lies in our lack of comprehension about the inflorescence morphological complexity of grasses. We focused our study on the PCK clade (named for phosphoenol pyruvate carboxykinase), a well-supported monoph...

Echinopepon disjunctus, a new species of the Echinopepon torquatus species-group from the Yungas rainforest of Jujuy (Argentina), is described and illustrated. Echinopepon coulteri is here excluded from the E. torquatus group on inflorescence and floral characters; a key to the remaining species of the group is included. In addition, the floral str...

Cucurbitaceae es una familia pantropical con 120 géneros y aproximadamente 830 especies, en su mayoría diclinomonoicas o dioicas. La flora argentina cuenta con 22 géneros y 54 especies distribuidas en el norte y el centro de nuestro país hasta los 40º 49’ de latitud sur. Para la Provincia de Salta se registran 14 géneros y 21 especies (5 escapadas...

Darwin encontró en las plantas pruebas de sus ideas sobre la evolución biológica, pero también halló un importante desafío en la dificultad de explicar la repentina aparición de las angiospermas en el registro fósil.

We describe and illustrate Cyclanthera oligoechinata (Cucurbitaceae, Sicyeae) a new species from southern Brazil (Paraná), northeastern Argentina (Misiones), and central and southern Paraguay (San Pedro). This new species resembles C. hystrix, C. eichleri and C. quinquelobata, but differs by its almost smooth fruits, and pistillate flowers and frui...

A developmental and anatomical study of the staminate flowers of Halophytum ameghinoi showed decussate tepal estivation; residual growth of the receptacle after stamen inception; monocotyledonous and basic types of anther wall development; secretory, binucleate tapetal cells; tetrahedral tetrads; and binucleate pollen grains. A vacuolate stage in t...

Inflorescence development in Panicum maximum and Urochloa plantaginea was comparatively studied with scanning electron and light microscopy to test the transfer of P. maximum to Urochloa and to look for developmental features applicable to future cladistic studies of the phosphoenol pyruvate carboxykinase (PCK) subtype of C(4) photosynthesis clade...

 Applying current data on cell differentia- tion and meiosis control to the early sporangial development in angiosperms, a strict relationship between cell lineage and its differentiation fate is rejected. An evaluation of cytological features indicative of a meiotic (sporogenous) fate discards the sterilization phenomenon and introduces the premei...

The chromsome number and karyotype ofHalophytum ameghinoi (Speg.) Speg. was found to be 2n = 24 and 12m+10sm+2t, respectively. Meiosis was regular and 12 bivalents were observed. The relationships of this monotypic family are briefly discussed.

According to previous authors, the South American genus Cucurbitella (Cucurbitaceae) includes six species, ostensibly separated by several diagnostic characters of dubious value. This study establishes the morphology of foliar primordia, the degree of stamen exsertion, and the shape and size of the petals and hypanthium as the only morphological ch...

Chaetium (Poaceae: Panicoideae: Paniceae) is a neotropical genus of three species, ranging from Mexico and the Antilles to northern South America. The genus is mainly defined by having an oblique articulation of the spikelet, a hairy callus at the base of the spikelet, and a linear hilum on the caryopsis. Morphological and anatomical characters wer...

Chaetium (Poaceae: Panicoideae: Paniceae) is a neotropical genus of three species, ranging from Mexico and the Antilles to northern South America. The genus is mainly defined by having an oblique articulation of the spikelet, a hairy callus at the base of the spikelet, and a linear hilum on the caryopsis. Morphological and anatomical characters wer...

Cucurbitaceae es una familia pantropical con 118 géneros y aproximadamente 825 especies, en su mayoría diclinomonoicas o dioicas. En general, estas plantas producen triterpenoides tetracíclicos oxigenados denominados cucurbitacinas, con sabor amargo y efecto purgante o abortivo. Muchas de ellas poseen valor económico, como las de los géneros Cucurb...

This paper deals with the ovular structure and development, gynosporogenesis and the selection mechanism of the functional gynospore in Cucurbitella duriaei and Cayaponia citrullifolia. Both species have 3-zonate ovular primordia, with epidermis, a subepidermal layer and an inner cellular group. The ovule is anatropous, bitegmic and crassinucellate...

This paper deals with the androsporangium development, androsporogenesis and androgametogenesis of 3 Argentine speeies of Cueurbitaeeae, with emphasis in the meehanism of anther dehiseenee and the possible physical link between the gametogenie eell and the siphonogenie nucleous within the androphyte (polien grain). The following are the main eonc1U...

This paper deals with the androsporangium development, androsporogenesis and androgametogenesis of 3 Argentine species of Cucurbitaceae, with emphasis in the mechanism of anther dehiscence and the possible physical link between the gametogenic cell and the siphonogenic nucleous within the androphyte (pollen grain). The following are the main conclu...

This paper deals with the ovule and anther structure, sporogenesis, and gametogenesis of Anreda cordifolia (Ten.) Steenis. The conclusions are: the anther wall develops according to the Monocotyledonous type of Davis (1966). The tapetum is secretory and the endothecial cells develop U-form thickenings on radial and internal tangential walls. Micros...

Asteraceae, Compositae, micro-morphology, section Otites, Senecio, series Otopteri, South America.