Daniel Gómez

Seasonal and Spatial Variations of Alkaloids in Merendera montana in Relation to Chemical Defense and Phenology

Merendera montana (Liliaceae) is an endemic plant broadly, but exclusively, occurring in the Iberian Peninsula where it is one of the most abundant species in rangelands grazed by sheep and on the routes used by migrating sheep herds. In spite of showing a peculiar phenology adapted to Mediterranean regions (leaves remain green from fall to spring and are absent in summer), this species has also successfully colonized high altitude environments (up to 2300 m), and abundant populations can be found in montane and subalpine pastures. Chemical analysis has shown a high forage quality as well as the pre- sence of tropolone alkaloids (similar to other species of the genus Merendera), mainly colchicine, 3-demethylcolchicine, and colchicoside. In general terms, the alkaloid content was significantly lower in the subterranean corms than in the leaves. No remarkable seasonal variations in total alkaloids was found, although an increase of colchicoside in the corms and a decrease of colchicine was noted in summer. Both chemical deterrents and phenology could be the cause of the widespread ecological adaptation of Merendera montana. The alkaloid content would prevent intake by wild herbivores during winter, while the absence of aerial organs in summer, coinciding exactly with the highest domestic herbivore pressure, would permit this species to colonize rich soil habitats where there is low plant competition.

Influence of livestock soil eutrophication on floral composition in the Pyrenees mountains

AbstractLivestock behaviour in the Pyrenees includes free grazing and a long resting period that provokes the accumulation of dung and urine in some places, so-called camping areas. The aims of this study were (i) to analyze any change in floral composition, and in nutritional and chemical contents of plants in a livestock camping area; and (ii) to relate the floral composition with soil chemical properties. In a linear transect, five sampling zones were established, from the centre of the camping area to the surrounding Nardus stricta-dominant pasture. The above ground plant biomass and the topsoil were sampled in each zone with 6 replicates per zone. Plant species were classified and weighed to calculate above ground biomass, nutritional and chemical contents, and Shannon diversity and evenness indices. Additionally, soils were sampled in two periods, at the beginning and at the end of grazing period. Soil available nutrients (nitrate, ammonium, phosphorus, potassium, calcium and magnesium), total nitrogen, organic carbon and pH were measured.Plant chemical contents (protein, lignin and others) were significantly related to the proportions of grasses, legumes and other plants; so, the protein content is positively correlated with legumes plant biomass while lignin content is negatively correlated with grasses. Both plant and soil nutrients increased linearly towards the centre of the camping area. However, the relationship among plant species richness, diversity and evenness relative to its position along the studied transect was bell-shaped. From the outskirts to the centre of the camping area, plants with low nutrient demand were progressively replaced by those with medium and high nutrients demand and by pioneers. Nardus stricta-dominant pasture has low plant diversity and plant nutrient content as well as a poor soil nutrient availability. The presence of the camping area introduced patches with more soil nutrients and new species in the large spatial scale. However at a small spatial scale, the strong soil nutrient concentration into the centre of the camping area reduced floral composition again. To ensure positive effects of camping areas on plant diversity, and to manage more effectively the nutrients returned to the soil, a reduction in the stocking rate should be pursued.

A Novel Method to Handle the Effect of Uneven Sampling Effort in Biodiversity Databases

How reliable are results on spatial distribution of biodiversity based on databases? Many studies have evidenced the uncertainty related to this kind of analysis due to sampling effort bias and the need for its quantification. Despite that a number of methods are available for that, little is known about their statistical limitations and discrimination capability, which could seriously constrain their use. We assess for the first time the discrimination capacity of two widely used methods and a proposed new one (FIDEGAM), all based on species accumulation curves, under different scenarios of sampling exhaustiveness using Receiver Operating Characteristic (ROC) analyses. Additionally, we examine to what extent the output of each method represents the sampling completeness in a simulated scenario where the true species richness is known. Finally, we apply FIDEGAM to a real situation and explore the spatial patterns of plant diversity in a National Park. FIDEGAM showed an excellent discrimination capability to distinguish between well and poorly sampled areas regardless of sampling exhaustiveness, whereas the other methods failed. Accordingly, FIDEGAM values were strongly correlated with the true percentage of species detected in a simulated scenario, whereas sampling completeness estimated with other methods showed no relationship due to null discrimination capability. Quantifying sampling effort is necessary to account for the uncertainty in biodiversity analyses, however, not all proposed methods are equally reliable. Our comparative analysis demonstrated that FIDEGAM was the most accurate discriminator method in all scenarios of sampling exhaustiveness, and therefore, it can be efficiently applied to most databases in order to enhance the reliability of biodiversity analyses.

El papel de los herbívoros en la conservación de los pastos

El Procambarus clarkii (cangrejo de rio americano o cangrejo rojo de las marismas) es un ejemplo de la introduccion de una especie en un ecosistema. En este trabajo se utiliza una poblacion de esta especie en la isla de Tenerife para un conjunto de actividades educativas en un Instituto de Formacion Profesional. Estas actividades incluyen muestreos y capturas de los cangrejos en el campo, la toma de sus medidas iniciales y su mantenimiento en el Instituto.Resumen de Tesis Doctoral. Director: Emilio Chuvieco Salinero. Centro: Departamento de Geografia, Programa interdepartamental de doctorado en Ciencias Ambientales. Fecha de lectura: 22 de Marzo de 2002.Francisco Diaz Pineda (pacopi@bio.ucm.es) es Catedratico de Ecologia en la Universidad Complutense de Madrid desde 1981. Estudio Biologia en la Universidad de Sevilla con ‘premio extraordinario’ (1973). Doctorado en 1975, su experiencia se basa en la planificacion territorial, el estudio de las bases ecologicas de la conservacion de la naturaleza, el analisis de ecosistemas mediterraneos - principalmente de pastizal - y la regulacion de la diversidad biologica. Es el actual Presidente de WWF–Espana (Adena) y miembro del International Board of WWF. Es miembro fundador del Centro Europeo de Conservacion de la Naturaleza (Ecnc) en Tilburg (Holanda) y componente de su actual Consejo Cientifico. Tambien es miembro del Capitulo espanol del Club de Roma desde 1999. Autor y editor de varios libros y monografias especializados, tiene 150 trabajos cientificos publicados y un centenar de articulos de divulgacion cientifica y opinion. Ha desarrollado 70 proyectos aplicados de ecologia por encargos o concursos nacionales, extranjeros o internacionales. Los premios recibidos incluyen el ‘Osborne’ (1975), el ‘Medio Ambiente sobre Estudios Tematicos’ (1984), el ’Ayuntamiento de Madrid’ (1986) y el ‘Premio Nacional de Medio Ambiente’ (2000). Jose Maria Rey Benayas le hizo la siguiente entrevista.

Teaching Environmental Sciences in an International and Interdisciplinary Framework: From Arid to Alpine Ecosystems in NE Spain

There is a growing need to develop, teach, and apply successful problem-solving and interdisciplinary approaches on environmental sciences education. Some of most effective learning activities are fieldwork, although sites to be visited have to be carefully selected to reduce time and expenses as well as to take account of safety concerns. That is the case for the teaching locations selected to develop an interdisciplinary, international, and intensive course in NE Spain. Within a distance of about 150 km, students can visit arid, Mediterranean, and Alpine environments, in one of the largest ecological gradients in Europe. In each environment, different sites are visited to analyse natural characteristics, ecological and socio-economic constraints and potentials, as well as the impact of the historical human utilisation in landscapes and ecosystems. Throughout the course, the participants focus on exploring sustainable land-use alternatives to developing rural areas in the visited environments. This teaching approach is aimed at students at degree, master, and Ph.D. level of biology, ecology, agriculture and forestry, landscape planning, and environmental technology. More than 400 students from different countries in Europe have participated since 1998 under the auspices of different SOCRATES and ERASMUS Intensive Programmes.