Charles Darwin y las glaciaciones más antiguas de Patagonia: los bloques erráticos del alto valle del Río Santa Cruz

Although the depositational environment assigned by Darwin to the large erratic blocks and gravels in the Río Santa Cruz valley has been reinterpreted, his geomorphological and stratigraphic observations are still in force. The large erratic blocks he described as crowning the Condor Cliff terrace and spread at the bottom of the valley just east of this locality (Sites 2 and 3), are now interpreted as indicators of the maximum glacial expansion in Patagonia. Similar blocks, though of a different lithology, accumulated over a lower terrace located up-valley (Site 4), are now linked to moraines and glacifluvial terraces of the Penultimate Glaciation. Finally, in addition to the erratic block discovered by Darwin in the lower Río Santa Cruz valley (Site 1), there are others - recently discovered - which probably account for a catastrophic event ascribed to a big glacier-lake outburst during the last interglacial.No obstante haber sido reinterpretado el ambiente depositacional asignado por Darwin a los grandes bloques erráticos y rodados del valle del río Santa Cruz, siguen vigentes sus observaciones geomorfológicas y estratigráficas. Los grandes bloques erráticos que describe coronando la terraza de Condor Cliff y dispersos en el fondo del valle inmediatamente al este de esta localidad (Sitios 2 y 3), son interpretados ahora como indicadores de la máxima expansión glaciaria de la Patagonia. Bloques similares, aunque de dispar litología, acumulados sobre una terraza más baja situada río arriba (Sitio 4), se vinculan actualmente a morenas y terrazas glacifluviales de la Penúltima Glaciación. Finalmente, al bloque errático descubierto por Darwin en el tramo inferior del valle del río Santa Cruz (Sitio 1), se le suman otros -de reciente descubrimiento- que probablemente den cuenta de un evento catastrófico atribuible al vaciamiento de un gran lago glaciar durante el último interglaciar.Fil: Malagnino, Eduardo Cayetano. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Strelin, Jorge Adrián. Universidad Nacional de Córdoba; Argentin

Role of immobilization of irradiated rats in the protective effect of bone marrow shielding

Rats were exposed to X-radiation to study the influence of immobilization and shielding of part of bone marrow during exposure on survival. It is concluded that (1) the beneficial effect of the stress factor (created by the immobilization of rats during exposure) can aggregate with the effect of bone marrow shielding and, under certain conditions, imitate the latter; and (2) the probability of the protective effect of immobilization should be taken into account when assessing the influence of bone marrow shielding

The interplay between ovule number, pollination and resources as determinants of seed set in a modular plant

Background. A classical dichotomous perspective proposes that either pollination or plant resources limit seed production. However, ovule number could also be limiting when pollination results in complete ovule fertilization and there are more plant resources available than needed to develop seeds. Moreover, this dichotomous view assumes that all flowers of a plant have equal access to a shared pool of resources, although these are frequently compartmentalized within plant modules, e.g. inflorescences. How ovule number, pollination and resources affect seed production in physiologicallycompartmentalized rather than physiologically-integrated plants has yet to be explored. We used raspberry (Rubus idaeus) to address this question.Methods. We first assessed if ovule number affected the fraction of ovules that develop into seed (i.e. seed set) and whether this effect related to the extent of physiological integration among flowers within plants. This was achieved by statistically testing predictions on the sign and level of plant organization (i.e. among flowers within inflorescences, among inflorescences within ramets, and among ramets) of the relation between ovule number and seed set given different degrees of physiological integration. We then explored whether the relation between ovule number and seed set was affected by plant age (used here as a surrogate of resource availability) and pollination intensity (open pollination vs. exclusion).Results. Within inflorescences, flowers with more ovules set a larger fraction of seeds. On the other hand, seed set at the inflorescence level was negatively related to the average number of ovules per flower. Seed set increased with ovule number and open-pollination, and decreased with ramet age. However, ovule number explained more variation in seed set than ramet age and pollination treatment. Ramet age affected the strength of the relation of seed set to ovule number, which was stronger in old than young ramets. Pollination did not alter the strength of this relation to any significant extent.Discussion. Results reveal the importance of ovule number as an overriding factor affecting seed set. Within inflorescences, resources appear to be differentially allocated to developing fruits from flowers with many ovules. This is consistent with the fact that in raspberry a large proportion of the carbon invested in fruit development is fixed by the inflorescence subtending leaf. Differential resource allocation to flowers with many ovules is not affected by pollinator exclusion, being stronger in resourceexhausted ramets. This suggests that the effects of pollen limitation and resource allocation are compartmentalized at the inflorescence level. Consequently, modular plants can be viewed as reproductive mosaics where either ovule number, pollination or resources limit the number of seeds set by different flowers, so that improvements in any of them could increase plant seed production.Fil: Strelin, Marina Micaela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Laboratorio de Ecotono; ArgentinaFil: Aizen, Marcelo Adrian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Laboratorio de Ecotono; Argentin

Estudio cuantitativo de la adaptación a los polinizadores en la subfamilia Loasoideae (Loasaceae), a través del estudio de la Alometría y la Ontogenia, integrando los enfoques Evo-Devo y Funcional.

Tesis (Grado Doctor en Ciencias Biológicas)--Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Lugar de Trabajo: Laboratorio de Ecología Evolutiva y Biología Floral. Instituto Multidisciplinario de Biología Vegetal-IMBIV-CONICET-Universidad Nacional de Córdoba. 2015 - 96 h. con Apéndice + CD. tabls.; ilus.; figus. Contiene Referencia Bibliográfica. Abstract en español e inglés.La morfología floral se expone a diferentes agentes selectivos a lo largo de la secuencia ontogenética que comprende al botón floral, a la flor funcional (esto es, la flor en condiciones de recibir y exportar polen) y al fruto.Dado que las morfologías expresada en estos estadios se interrelacionan, se espera que la selección que afecta a un estadio puntual de la ontogenia tenga efectos colaterales sobre la adecuación de otras etapas ontogenéticas. Esta secuencia ontogenética toma a su vez lugar dentro de un contexto más amplio, la inflorescencia, donde las flores están sujetas a selección de manera colectiva. Se espera que dicha asociación funcional de las flores dentro de las inflorescencias, en conjunto con la interdependencia de la adecuación de distintos estadios del desarrollo, sesgue el material sobre el cual la selección puede actuar en las flores funcionales. A pesar de estos sesgos ontogenéticos a los cuales podría estar sujeta la evolución floral, la diversidad floral es copiosa. Entender la relación entre la ontogenia floral y los patrones de diversificación floral es lo que motiva esta tesis. En particular, examiné esta pregunta en la subfamilia de angiospermas Loasoideae (Loasaceae), la cual se habría diversificado recientemente en los Andes Centrales en respuesta a cambios en el ambiente de polinizadores. Para llevar adelante este trabajo en primer lugar clarifiqué el contexto adaptativo en el cual ocurrió la diversificación de la morfología floral de Loasoideae (Loasaceae). Para ello describí la forma floral con variables morfogeométricas y modelé estas variables utilizando técnicas novedosas de análisis comparativo. A través de ello establecí que la morfología floral en el género Caiophora (Loasoideae, Loasaceae) se habría diversificado en respuesta a cambios en ambiente de polinizadores, posiblemente en el contexto de una radiación adaptativa. También establecí que la optimización de la morfología floral de Loasoideae a diferentes estrategias de polinización estaría mediada por un trade-off (compensación) entre la polinización mediada por himenópteros y la mediada por colibríes. Esto aportó un marco para abordar las siguientes preguntas: 1) La morfología floral en especies con la misma estrategia de polinización ¿posee un patrón de desarrollo común?- 2) La diversificación adaptativa de Caiophora (Loasoideae, Loasaceae), ¿estuvo sesgada por la variación presente a lo largo de la trayectoria de desarrollo ancestral? Intenté responder a estas preguntas utilizando métodos adecuados recientemente propuestos, los cuales permiten el análisis de datos morfogeométricos en estudios de evolución del desarrollo (informalmente “evo-devo”).Los resultados de esta tesis sugieren que las asociaciones entre la forma y el tamaño presentes a lo largo de la trayectoria de desarrollo ancestral no habrían sesgado la diversificación morfológica de Caiophora. Sin embargo, algunas variantes de forma presentes a lo largo de la ontogenia ancestral habrían facilitado la adaptación a la polinización mediada por colibríes y a la polinización mediada por roedores en el género

Reconstruction of the late quaternary glacial geology on King George Island, South Shetland Islands: First steps of a geoscientific project

King George Island (Isla 25 de Mayo) is the largest one of the South Shetland Islands (SShI). This archipelago is located approximately 120 km NW of the Antarctic Peninsula, from which it is separated by the Bransfield Strait (Mar de la Flota). The SShI are located just south of the Antarctic Convergence Zone in a key location for investigating glacial and climatic fluctuations relative to both the Southern Hemisphere and the rest of Antarctica. The geomorphology and glacier geology of the SShI (Sugden and John 1973, Hall 2003 and 2007, Del Valle et al. 2007, Strelin 2010, Simms et al. 2011) constitutes a fragmentary record. Despite the deglaciation, inland ice free areas are scarce and are strongly affected by the thaw with the consequent destruction of previous geoforms. The few obtained radiocarbon ages on land exposures have poor stratigraphic control being necessary to consider the problems of pollution and the reservoir effect that affect them. Based on geochemical and sedimentological proxies and radiocarbon dating in sedimentary cores obtained from bays, some glaciers advances and warm periods have been inferred for the middle and late Holocene, among them are those corresponding to the Medieval Climate Optimum and the Little Ice Age (LIA) (Yoon et al. 2000 and 2004, Hass et al. 2010, Monien et al. 2011). It should be noted that for some glaciological reconstructions based on organic radiocarbon dating on marine sediments the ages are still questionable. Often it does not exist yet a clear criteria of correlation that allow to link between glaciterrestrial sediments and glacimarine ones. The study of the glacial, periglacial and coastal marine record of King George Island has a particular importance to enhance the knowledge of its paleoenvironmental evolution since the Marine Isotopic Stage 3 (MIS 3). There is no precision on the beginning and end of the Last Glacial Maximum (LGM), nor on the rhythm of the deglaciation post-LGM, known as Termination 1, both for coastal and marine areas, as well as offshore areas from King George Island. In the same way, it´s not known if there was a glacial advance linked with the Antarctic Cold Reversal clearly detectable in Antarctic ice cores or sediment deposits in southern Patagonian exposures (Strelin et al. this congress). The way in which the deglaciation continued during the early Holocene, the peak of the Holocene marine transgression (Strelin et al. this Congress), the later chronology of the Neoglacial advances, including the LIA, and the warmer periods that separate them are as well topics to deepen. The objective of this project is to study and date the geomorphological and glaciterrestrial evidences linked to the glacial history in the area of South Shetland Islands, since MIS 3, correlate them with bathymetric records and proxies from marine cores and discuss its link with other sectors of the Antarctic Peninsula, particularly with James Ross Islan

Delayed differentiation of epidermal cells walls can underlie pedomorphosis in plants: the case of pedomorphic petals in the hummingbird-pollinated Caiophora hibiscifolia (Loasaceae, subfam. Loasoideae) species

Understanding the relationship between macroevolutionary diversity and variation in organism development is an important goal of evolutionary biology. Variation in the morphology of several plant and animal lineages is attributed to pedomorphosis, a case of heterochrony, where an ancestral juvenile shape is retained in an adult descendant. Pedomorphosis facilitated morphological adaptation in different plant lineages, but its cellular and molecular basis needs further exploration. Plant development differs from animal development in that cells are enclosed by cell walls and do not migrate. Moreover, in many plant lineages, the differentiated epidermis of leaves, and leaf-derived structures, such as petals, limits organ growth. We, therefore, proposed that pedomorphosis in leaves, and in leaf-derived structures, results from delayed differentiation of epidermal cells with respect to reproductive maturity. This idea was explored for petal evolution, given the importance of corolla morphology for angiosperm reproductive success

Exploring the ontogenetic scaling hypothesis during the diversification of pollination syndromes in <i>Caiophora</i> (Loasaceae, subfam. Loasoideae)

Phenotypic diversification of flowers is frequently attributed to selection by different functional groups of pollinators. During optimization of floral phenotype, developmental robustness to genetic and non-genetic perturbations is expected to limit the phenotypic space available for future evolutionary changes. Although adaptive divergence can occur without altering the basic developmental programme of the flower (ontogenetic scaling hypothesis), the rarity of reversion to ancestral states following adaptive radiations of pollination syndromes suggests that changes in the ancestral developmental programme of the flower are common during such evolutionary transitions. Evidence suggests that flower diversification into different pollination syndromes in the Loasoideae genus Caiophora took place during a recent adaptive radiation in the central Andes. This involved transitions from bee to hummingbird and small rodent pollination. The aim of this work was to examine if the adaptive radiation of pollination syndromes in Caiophora occurred through ontogenetic scaling or involved a departure from the ontogenetic pattern basal to this genus.Fil: Strelin, Marina Micaela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Benitez-Vieyra, Santiago Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Fornoni, Juan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina. Universidad Nacional Autónoma de México; MéxicoFil: Klingenberg, Christian Peter. University of Manchester; Reino UnidoFil: Cocucci, Andrea Aristides. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentin

Paleoenvironmental Evolution of Potter Peninsula during the Holocene, King George Island, South Shetland Islands

The first Holocene marine transgression reached the inner fiords of King George Island approximately at 9.5 ka BP according to Sugden and John (1973). This age marks today the minimum age of the end of the last glacial period obtained on land and the start of the Holocene in this Antarctic sector. Following the first Holocene marine transgression, Watcham et al. (2011) reconstructed a relative sea level curve for the South Shetland Islands with a relative sea level rise of 15.5 m amsl for Fildes Peninsula between 8 and 7 ka BP. The curve shows that a delay occurred in the isostatic uplift after 7.2 ka BP related to a glacier still-stand resulting in a relative sea level rise. This is followed by a drop of the relative sea level after 7 ka BP due to the rate of glacial unloading and isostatic rebound exceeding the rate of eustatic sea level rise. The aim of this presentation is to show new evidence, which will help to understand the postglacial paleoenvironmental changes on King George Island. Our chrono-stratigraphical and geomorphological studies in Potter Peninsula suggest, that the Holocene post-glacial marine transgression was not just initiated before 7.7 ka BP but also reached 14 m amsl, and was locally interrupted by a glacier advance after 7.3 ka BP. This glacier advance can be correlated to Watcham´s et al (2011) curve, showing a drop of relative sea level between 7.2 and 7 ka BP. In conclusion, we consider that a glacier readvance took place between 7.2 and 7 ka BP in the Southern sector of King George Island. Additionally our findings show that the age of 9.5 ka BP as a minimum age of the onset of the Holocene transgression in the South Shetland Islands has to be reconsidered. References Sugden, D. and John, B., 1973. The age of glacier fluctuations in the South Shetland Islands,Antarctica. In: van Zinderen Bakker, E.M. (Ed.), Palaeoecology of Africa, the Surrounding Islands, and Antarctica. A.A. Balkema, 139-159 p., Cape Town. Watcham, E. P., Bentley, M. J., Hodgson, D. A., Roberts, S. J., Fretwell, P. T., Lloyd, J. M., Larter, R. D., Whitehouse, P. L., Leng, M. J., Monien, P. and Moreton, S. G., 2011. A new Holocene relative sea level curve for the South Shetland Islands, Antarctica. Quaternary Science Reviews 30, 3152–3170

Holocene deglaciation and glacier readvances on the Fildes Peninsula and King George Island (Isla 25 de Mayo), South Shetland Islands, NW Antarctic Peninsula

To provide insights into glacier-climate dynamics of the South Shetland Islands (SSI), NW Antarctic Peninsula, we present a new deglaciation and readvance model for the Bellingshausen Ice Cap (BIC) on Fildes Peninsula and for King George Island/Isla 25 de Mayo (KGI) ~62°S. Deglaciation on KGI began after c. 15 ka cal BP and had progressed to within present-day limits on the Fildes Peninsula, its largest ice-free peninsula, by c. 6.6–5.3 ka cal BP. Probability density phase analysis of chronological data constraining Holocene glacier advances on KGI revealed up to eight 95% probability ‘gaps’ during which readvances could have occurred. These are grouped into four stages – Stage 1: a readvance and marine transgression, well-constrained by field data, between c. 7.4–6.6 ka cal BP; Stage 2: four probability ‘gaps’, less well-constrained by field data, between c. 5.3–2.2 ka cal BP; Stage 3: a well-constrained but restricted ‘readvance’ between c. 1.7–1.5 ka; Stage 4: two further minor ‘readvances’, one less well-constrained by field data between c. 1.3–0.7 ka cal BP (68% probability), and a ‘final’ well-constrained ‘readvance’ after 1950 CE) is associated with recent warming/more positive SAM-like conditions