Surviving despite difficulties: amphibians and the perpetuation of the species

Els amfibis són actualment un dels grups de vertebrats més amenaçats del món. Les causes són diverses i quasi totes d’origen antròpic. Malgrat aquest declivi generalitzat, encara existeix una gran biodiversitat d’amfibis. En general, aquest grup, com que tenen un cicle biològic bifàsic (fase larvària aquàtica i fase adulta terrestre) és especialment sensible a la disminució i a la desaparició de les seves poblacions, fonamentalment per modificació dels seus hàbitats. Es pot pensar que, com a grup, els amfibis tenen dificultats intrínseques per a la seva supervivència, però la realitat està molt lluny d’aquesta afirmació. L’inici de la història evolutiva d’aquest grup, a partir dels peixos sarcopterigis, representa el primer pas per accedir a terra ferma i aprofitar uns recursos que abans no estaven al seu abast. Així doncs, la seva diversificació ha comportat una variabilitat d’estratègies de reproducció sorprenents. Aquest article esmenta el pas a terra ferma i fa una revisió de les estratègies reproductores dels amfibis que els han permès, malgrat les adversitats, distribuir-se àmpliament i sobreviure fins als nostres dies.Amphibians are currently one of the most threatened vertebrate groups in the world. There are many reasons for this problem, but almost all of them are of anthropogenic origin. However, despite this widespread decline, there is still a great biodiversity of amphibians. They have a biphasic life cycle (an aquatic larval stage and a terrestrial adult stage) and are usually especially prone to reduction and extinction of their populations, particularly as a result of modification of their habitats. It might therefore be thought that amphibians have intrinsic difficulties for survival, but this is far from being true. The beginning of their evolutionary history, from sarcopterygian fishes, was the first step towards reaching land and taking advantage of new resources, and their diversification has led to a surprising variety of reproduction strategies. This paper deals with the move to land and reviews the reproductive strategies of amphibians that have allowed them, despite adversity, to spread widely and survive to this day

Tritón pirenaico – Calotriton asper (Dugès, 1852)

Anfibios - Orden Caudata - Familia Salamandridae en la Enciclopedia Virtual de Vertebrados Españoles, http://www.vertebradosibericos.org/. Versiones anteriores: 17-03-2008; 12-03-2009; 21-07-2014A comprehensive review of the natural history of the Pyrenean brook newt Calotriton asper in Spain.Peer reviewe

Modelos computacionales para simulación de guerra antiaérea y antisubmarina

This paper describes the generation and simulation process of computational models oriented to the analysis of the operational situations (OPSIT) of anti-air warfare (AAW) and antisubmarine warfare (ASW), with the purpose of evaluating the effectiveness of different combinations of threats, weapons, and sensors of the Colombian Navy. A detailed description of the OPSITs modeling process is presented by using the selected discrete events simulation tool. The experiments design process and the statistical analysis of the results is also described, using a statistical analysis tool. All this to provide the Colombian Navy with a tool it can use to evaluate the systems that could be part of future units.El documento describe el proceso de generación y simulación de modelos computacionales orientados hacia el análisis de unas situaciones operacionales de guerra antiaérea (AAW) y Antisubmarina (ASW), con el fin de evaluar la efectividad de diferentes combinaciones de amenazas, armas y sensores de la Marina Colombiana. Se presenta una descripción detallada del proceso de modelación de las situaciones operacionales en la herramienta de simulación de eventos discretos seleccionada, así como también se describe el proceso de diseño de los experimentos y el tratamiento estadístico de los resultados, empleando una herramienta de análisis estadístico. Lo anterior tendiente a proporcionar a la Armada Colombiana, una herramienta para la evaluación de los sistemas que podrían componer las futuras unidades

Trophic strategies of a non-native and a native amphibian species in shared ponds.

One of the critical factors for understanding the establishment, success and potential impact on native species of an introduced species is a thorough knowledge of how these species manage trophic resources. Two main trophic strategies for resource acquisition have been described: competition and opportunism. In the present study our objective was to identify the main trophic strategies of the non-native amphibian Discoglossus pictus and its potential trophic impact on the native amphibian Bufo calamita.We determine whether D. pictus exploits similar trophic resources to those exploited by the native B. calamita (competition hypothesis) or alternative resources (opportunistic hypothesis). To this end, we analyzed the stable isotope values of nitrogen and carbon in larvae of both species, in natural ponds and in controlled laboratory conditions. The similarity of the δ15N and δ13C values in the two species coupled with isotopic signal variation according to pond conditions and niche partitioning when they co-occurred indicated dietary competition. Additionally, the non-native species was located at higher levels of trophic niches than the native species and B. calamita suffered an increase in its standard ellipse area when it shared ponds with D. pictus. These results suggest niche displacement of B. calamita to non-preferred resources and greater competitive capacity of D. pictus in field conditions. Moreover, D. pictus showed a broader niche than the native species in all conditions, indicating increased capacity to exploit the diversity of resources; this may indirectly favor its invasiveness. Despite the limitations of this study (derived from potential variability in pond isotopic signals), the results support previous experimental studies. All the studies indicate that D. pictus competes with B. calamita for trophic resources with potential negative effects on the fitness of the latter

Projecte d'atlas electrònic del crani : innovació docent a les pràctiques de vertebrats

L'assignatura de Vertebrats s'imparteix dins el segon cicle de la llicenciatura de Biologia, tant a la Universitat Autònoma de Barcelona com a la Universitat de Barcelona. La matèria pròpia d'aquesta assignatura es caracteritza per la seva amplitud temàtica, així com per la dificultat intrínseca que comporten els continguts referents a aspectes morfològics. De manera particular, una de les estructures que per la seva complexitat sempre resulta difícil d'assimilar per part dels estudiants és el crani. Tradicionalment, durant les pràctiques de laboratori els alumnes examinen i interpreten diferents peces anatòmiques des del punt de vista comparat i és freqüent que, degut a la quantitat de material a consultar i a la poca durada relativa de les sessions pràctiques, no hi hagi temps suficient per poder assimilar amb profunditat certes observacions referents al crani. Per tal de facilitar la comprensió d'aquesta estructura, professors de les Universitats esmentades estan elaborant, a partir fonamentalment de material i imatges pròpies, un atlas electrònic del crani, en el que es presta una atenció molt particular al binomi estructura-funció, relació que facilita notablement la interpretació morfològica des dels punts de vista evolutiu i adaptatiu. Mitjançant aquest atlas s'esperen obtenir resultats positius en els següents aspectes: i) una millor comprensió del pla estructural del crani; ii) un increment en la capacitat de síntesi dels alumnes; iii) completar l'aprenentatge teòric amb observacions de les peces anatòmiques, constatant la seva modificació al llarg de l'evolució; iv) una millora de la qualitat docent i de la coordinació del professorat que imparteix l'assignatura. Un cop completades les diferents seccions de l'atlas, es té previst programar una sèrie d'activitats d'autoavaluació sobre la informació proporcionada, així com realitzar una enquesta a l'alumnat per tal de valorar i, en el seu cas, millorar el material presentat

Estimación de la cantidad de potencia suministrada por las celdas fotovoltaicas de un cubesat

CubeSats are small satellites that due to their size restriction have photovoltaic cells placed on theirs surface as the only energy source. The purpose of this work is to estimate the maximum amount of power that can be obtained from these solar cells, so that an energy balance can be made during the design of space mission with this kind of satel­lites. In the analyzed scenario, a CubeSat of 10cm x 10cm x 10cm (1U) has always a face oriented toward the Earth. Cosine loss and the temperature variation due to satellite orbit are considered. For the estimation we use a mathematical model of the solar cells, which is also used to estimate the maximum power point according to the incidence angle of the solar radiation and the temperature on a low orbit around the Earth. The results show the variation of the maximum electric power sup­plied by the panels on the illuminated portion of the orbit, without considering the Earth's albedo. Apart from the power, the current -voltage curves are estimated for different locations over the CubeSat's orbit.Los CubeSat son pequeños satélites que, debido a las restricciones propias de sus dimensiones, tienen como única fuente de energía celdas foto-voltaicas sobre su superficie. El propósito de este artículo es estimar la cantidad máxima de poten­cia que puede obtenerse de estas celdas solares, de manera que sea posible realizar un balance de energía cuando se diseñan misiones espaciales con este tipo de satélites. En el escenario anali­zado, un CubeSat de 10cm x 10cm x 10cm (1U) tiene una cara siempre orientada hacia la Tierra. Se consideran las pérdidas por el coseno del ángulo y la variación de la temperatura debido a la órbita del satélite. Para la estimación se usa un modelo matemático de las celdas solares, con el cual se calcula el punto de máxima potencia se­gún el ángulo de incidencia de la radiación solar y la temperatura sobre una órbita baja alrededor de la Tierra. Los resultados muestran la variación de la potencia eléctrica máxima suministrada por los paneles sobre la porción iluminada de la órbi­ta, sin considerar el albedo de la Tierra. Además de la potencia, se estiman las curvas corriente-voltaje para diferentes ubicaciones sobre la órbi­ta del CubeSat

Micro-hotspots for conservation: an umbrella tree species for the unique Socotran reptile fauna

Umbrella species are defined as species that can be rare and sensitive to human disturbance, whose protection may confer the protection of other co-occurring species. The dragon's blood tree Dracaena cinnabari Balf.f. was already considered an umbrella species on Socotra Island (Indic Ocean, Yemen) due to its ecological importance for some native biota. We studied the reptile community living on D. cinnabari from Socotra Island. We sampled reptiles on trees across most D. cinnabari populations and applied co-occurrence and network partition analyses to check if the presence of reptiles on D. cinnabari populations was random or structured. Regardless of its patched and scarce actual distribution, we report the use of this tree as a habitat by more than half of the reptile community (12 endemic reptiles). Co-occurrence and network partition analyses demonstrate that this community is structured across the distribution of dragon's blood trees, reflecting complex allopatric, vicariant, and biotic interaction processes. Hence, these trees act as micro-hotspots for reptiles, that is, as areas where endemic and rare species that are under threat at the landscape scale co-occur. This Socotra endemic tree is currently threatened by overgrazing, overmaturity, and climate change. Its protection and declaration as an umbrella species are expected to benefit the reptile community and to protect evolutionary processes that are partially driven by the ecological links between reptiles and this tree. To our knowledge, no tree species has been proposed as an umbrella species for island vertebrate endemics so far, highlighting the ecological uniqueness of Socotra Island

Observations on the intraspecific variation in tadpole morphology in natural ponds

Intraspecific morphological variation of anuran tadpoles occurs in response to several factors. Causes and consequences of this variation have been largely studied hitherto in controlled environments, but data from natural habitats is clearly less abundant. Here, we present a series of observations on the morphology – mainly tail depth – of three tadpole species from NE Iberian Peninsula across different pond typologies. According to experimental data on tadpole morphology and selective pressures along the pond permanency gradient, we should expect that tadpoles inhabiting ponds with a short hydroperiod – mainly facing desiccation risk – have shallower tail fins than tadpoles from ponds with longer hydroperiod – mainly facing predation risk. Thus, we expected that the link between these complementary selective pressures – predation risk, desiccation risk – and hydroperiod could make possible to detect intraspecific variation in tadpole morphology among different typologies of natural ponds. Morphological differences were found in all studied species, and variation, when present, agreed with theory: tadpoles had deeper fin tails as they were collected in ponds with a longer hydroperiod. Interestingly, in most cases these morphological differences were more marked as tadpoles were larger in size. Although distances among the studied ponds were generally short – posing phenotypic plasticity as the most plausible proximate mechanism – specifically designed studies would be needed to disentangle the relative role of other processes like local adaptation

A computational model approach to assess the effect of climate change on the growth and development of tadpoles

All of the environmental conditions in nature act on an organism simultaneously. However, in experimental studies of the factors influencing metamorphosis, each factor needs to be examined individually in order to disentangle its specific effects. However, it is challenging to then build properly integrated models which include data on all of the different factors evaluated in different experiments. This study set out to develop a predictive model which could synthesize the results of several experiments on survival, development and growth of Natterjack toad (Epidalea calamita) tadpole guilds. The proposed Population Dynamic P System (PDP) model enables estimates of growth and development during the larval phase, under different environmental conditions, weather conditions, predator density, and pond characteristics and management. The architecture of the model allows the inclusion of an indefinite number of parameters and interactions, with all inputs interacting in parallel, and enables solutions to complex modeling approaches. Using the model with a range of field data, we found that the importance of predation pressure on Natterjack toad tadpole guilds exceeds the potential effects of variations in temperature and precipitation. The impact of introduced invasive predators therefore arguably poses the greatest threat to this species. This type of model holds promise as a reliable management and conservation tool for this and other species, especially where interactions between environmental factors make the impacts of individual factors difficult to predict