Estudios taxonómicos en el género Festuca L. (Poaceae) de Argentina y Chile

In this contribution we analyze the morphological and anatomical variation in the complex of species related to Festuca chrysophylla using multivariate analysis. We describe the morphology of F. chrysophylla, synonyms are established and the geographical distribution is updated. We establish one new synonymy: F. orthophylla under F. chrysophylla. Furthermore, based on herbarium material, we provide the first record for F. werdermannii for Argentina. We describe in detail the anatomy of both species based on the study of numerous specimens. We select lectotypes for F. chrysophylla and F. deserticola var. juncea.En esta contribución se analiza la variación morfológica en el complejo de especies relacionadas a Festuca chrysophylla por medio de análisis estadísticos multivariados de caracteres morfológicos y anatómicos. Se describe la morfología de F. chrysophylla, se establecen sus sinónimos y se actualiza su distribución geográfica. Se establece un nuevo sinónimo: F. orthophylla bajo F. chrysophylla. Asimismo, sobre la base del estudio de material de herbario se registra por primera vez la presencia de Festuca werdermannii para Argentina, hasta ahora sólo conocida para Chile. Se describe detalladamente la anatomía foliar para ambas especies sobre la base del estudio de numerosos ejemplares. Se seleccionan lectotipos para F. chrysophylla y para F. deserticola var. juncea

Macro-Climatic Distribution Limits Show Both Niche Expansion and Niche Specialization among C4 Panicoids

Grasses are ancestrally tropical understory species whose current dominance in warm open habitats is linked to the evolution of C4 photosynthesis. C4 grasses maintain high rates of photosynthesis in warm and water stressed environments, and the syndrome is considered to induce niche shifts into these habitats while adaptation to cold ones may be compromised. Global biogeographic analyses of C4 grasses have, however, concentrated on diversity patterns, while paying little attention to distributional limits. Using phylogenetic contrast analyses, we compared macro-climatic distribution limits among ~1300 grasses from the subfamily Panicoideae, which includes 4/5 of the known photosynthetic transitions in grasses. We explored whether evolution of C4 photosynthesis correlates with niche expansions, niche changes, or stasis at subfamily level and within the two tribes Paniceae and Paspaleae. We compared the climatic extremes of growing season temperatures, aridity, and mean temperatures of the coldest months. We found support for all the known biogeographic distribution patterns of C4 species, these patterns were, however, formed both by niche expansion and niche changes. The only ubiquitous response to a change in the photosynthetic pathway within Panicoideae was a niche expansion of the C4 species into regions with higher growing season temperatures, but without a withdrawal from the inherited climate niche. Other patterns varied among the tribes, as macro-climatic niche evolution in the American tribe Paspaleae differed from the pattern supported in the globally distributed tribe Paniceae and at family level.Fil: Aagesen, Lone. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica Darwinion. Academia Nacional de Ciencias Exactas, Físicas y Naturales. Instituto de Botánica Darwinion; ArgentinaFil: Biganzoli, Fernando. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Métodos Cuantitativos y Sistemas de Información; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Bena, María Julia. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica Darwinion. Academia Nacional de Ciencias Exactas, Físicas y Naturales. Instituto de Botánica Darwinion; ArgentinaFil: Godoy Bürki, Ana Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica Darwinion. Academia Nacional de Ciencias Exactas, Físicas y Naturales. Instituto de Botánica Darwinion; ArgentinaFil: Reinheimer, Renata. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Agrobiotecnología del Litoral. Universidad Nacional del Litoral. Instituto de Agrobiotecnología del Litoral; ArgentinaFil: Zuloaga, Fernando Omar. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica Darwinion. Academia Nacional de Ciencias Exactas, Físicas y Naturales. Instituto de Botánica Darwinion; Argentin

A molecular phylogeny of the genus Alloteropsis (Panicoideae, Poaceae) suggests an evolutionary reversion from C4 to C3 photosynthesis

The grass Alloteropsis semialata is the only plant species with both C(3) and C(4) subspecies. It therefore offers excellent potential as a model system for investigating the genetics, physiology and ecological significance of the C(4) photosynthetic pathway. Here, a molecular phylogeny of the genus Alloteropsis is constructed to: (a) confirm the close relationship between the C(3) and C(4) subspecies of A. semialata; and (b) infer evolutionary relationships between species within the Alloteropsis genus

Zygostates alleniana (Orchidaceae: Epidendroideae: Cymbidieae: Oncidiinae): estructura floral relacionada con la polinización

The genus Zygostates Lindl. (Orchidaceae) comprises about 20 species of small Neotropical epiphytic plants, represented in its southernmost limit by the species Z. alleniana. In this paper, we studied morphological and anatomical floral characteristics of this species related to pollination mechanism. We confirmed the presence of the unicellular trichomes on the base of the lip and side lobes secreting oil, constituting a trichomal elaiophore. The oil is deposited beneath the cuticle at the apex of the trichomes forming small blisters. The oil could represent a reward for the species Lophopedia nigrispinis, which would be a potential pollinator of Z. alleniana in a natural area within the geographic range of this plant species. Moreover, we prove that the reconfiguration of the pollinaruim is due to the dehydration of the walls cell. This reconfiguration could favor cross-pollination mechanism already described for other species of the family Orchidaceae. Finally, we discuss the floral characters present in Z. alleniana with closely related species.El género Zygostates Lindl. (Orchidaceae) comprende aproximadamente 20 especies de pequeñas plantas epífitas con distribución neotropical, representado en su límite más austral por la especie Z. alleniana. En el presente trabajo se estudian morfológica y anatómicamente las características florales de esta especie relacionadas con el mecanismo de polinización. Se confirma la presencia de tricomas unicelulares en la base del labelo y lóbulos laterales que actúan secretando aceite, constituyendo un elaióforo tricomatoso. El aceite se deposita por debajo de la cutícula en el ápice de los tricomas formando pequeñas ampollas. El aceite podría representar una recompensa para la especie Lophopedia nigrispinis, la cual sería un posible polinizador de Z. alleniana en un área natural dentro del rango de distribución geográfica de esta especie vegetal. Por otro lado, se comprueba que la reconfiguración del polinario se debe a la deshidratación de las paredes celulares. Esta reconfiguración podría favorecer la polinización cruzada, mecanismo ya descrito para otras especies de la familia Orchidaceae. Por último, se discuten los caracteres florales presentes en Z. alleniana con otras especies estrechamente emparentadas

Five Nuclear Loci Resolve the Polyploid History of Switchgrass (Panicum virgatum L.) and Relatives

Polyploidy poses challenges for phylogenetic reconstruction because of the need to identify and distinguish between homoeologous loci. This can be addressed by use of low copy nuclear markers. Panicum s.s. is a genus of about 100 species in the grass tribe Paniceae, subfamily Panicoideae, and is divided into five sections. Many of the species are known to be polyploids. The most well-known of the Panicum polyploids are switchgrass (Panicum virgatum) and common or Proso millet (P. miliaceum). Switchgrass is in section Virgata, along with P. tricholaenoides, P. amarum, and P. amarulum, whereas P. miliaceum is in sect. Panicum. We have generated sequence data from five low copy nuclear loci and two chloroplast loci and have clarified the origin of P. virgatum. We find that all members of sects. Virgata and Urvilleana are the result of diversification after a single allopolyploidy event. The closest diploid relatives of switchgrass are in sect. Rudgeana, native to Central and South America. Within sections Virgata and Urvilleana, P. tricholaenoides is sister to the remaining species. Panicum racemosum and P. urvilleanum form a clade, which may be sister to P. chloroleucum. Panicum amarum, P. amarulum, and the lowland and upland ecotypes of P. virgatum together form a clade, within which relationships are complex. Hexaploid and octoploid plants are likely allopolyploids, with P. amarum and P. amarulum sharing genomes with P. virgatum. Octoploid P. virgatum plants are formed via hybridization between disparate tetraploids. We show that polyploidy precedes diversification in a complex set of polyploids; our data thus suggest that polyploidy could provide the raw material for diversification. In addition, we show two rounds of allopolyploidization in the ancestry of switchgrass, and identify additional species that may be part of its broader gene pool. This may be relevant for development of the crop for biofuels

C4 photosynthesis promoted species diversification during the Miocene grassland expansion.

Identifying how organismal attributes and environmental change affect lineage diversification is essential to our understanding of biodiversity. With the largest phylogeny yet compiled for grasses, we present an example of a key physiological innovation that promoted high diversification rates. C4 photosynthesis, a complex suite of traits that improves photosynthetic efficiency under conditions of drought, high temperatures, and low atmospheric CO2, has evolved repeatedly in one lineage of grasses and was consistently associated with elevated diversification rates. In most cases there was a significant lag time between the origin of the pathway and subsequent radiations, suggesting that the 'C4 effect' is complex and derives from the interplay of the C4 syndrome with other factors. We also identified comparable radiations occurring during the same time period in C3 Pooid grasses, a diverse, cold-adapted grassland lineage that has never evolved C4 photosynthesis. The mid to late Miocene was an especially important period of both C3 and C4 grass diversification, coincident with the global development of extensive, open biomes in both warm and cool climates. As is likely true for most "key innovations", the C4 effect is context dependent and only relevant within a particular organismal background and when particular ecological opportunities became available