New publication: Demography of the critically endangered Balearic shearwater: impacts of fisheries and time to extinctionWorld-wide, many seabirds are affected by fisheries in opposing ways: as a source of mortality from bycatch, but also by providing discards as a predictable and abundant food resource. This applies to the Balearic shearwater Puffinus mauretanicus, the most endangered European seabird, whose time to extinction was estimated at only ˜40 years a decade ago.Since the previous assessment, new data and more sophisticated demographic modelling have become available, and new fishing policies from the European Union (Common Fisheries Policy, CFP) will apply, posing different scenarios for the viability of the species. Thus, there is both an urgent need and an opportunity for a more reliable update of the conservation status of the species.Demographic data were collected between ...
Posted Mar 11, 2016, 3:01 AM by David Alvarez
New publication: Census method comparision in an urban population of Fire salamanderAmphibians are the most threatened vertebrates on Earth, and one of the main factors involved in their decline is the loss and fragmentation of their natural habitats. Contemporary urban development is a major cause of habitat fragmentation, and populations trapped within urban environments offer a unique opportunity to study effects of fragmentation. Here we compared, for the first time in fire salamanders (Salamandra salamandra), estimates of census (N) and effective population size (Ne) in a small urban population in the city of Oviedo (Spain). We performed a four year capture-mark-recapture study and used three single-sample Ne estimators based on 58 individuals genotyped for 15 polymorphic microsatellite loci. Our study showed a small (N̂=113 salamanders; 95% CI ...
Posted Mar 11, 2016, 2:56 AM by David Alvarez
New book: Los vencejos sueñan despiertos (in Spanish)Ya está disponible el libro "Los vencejos sueñan despiertos", editado por la Tundra Ediciones. En este libro se recogen mas de 100 artículos que he publicado en el blog Naturaleza Cantábrica y otros inéditos escritos para este libro. La temática es muy variada, incluyendo textos de divulgación científica sobre Ecología evolutiva, la Selección sexual, la ecología o el cambio climático. Asimismo se hace una revisión crítica sobre varios de los problemas de conservación de la naturaleza y sobre todo de la gestión de la misma.Los artículos se han agrupado en las siguientes secciones:ÍNDICEPrólogo1. Evolución y selección natural.2. La evolución sí que es una historia de sexo y no las sombras de Grey.3. Amigos, enemigos ...
Posted Mar 11, 2016, 2:53 AM by David Alvarez
New publication: Sperm competition in frogs differs among populations with different breeding systems
In species with simultaneous
polyandry, male-biased operational sex-ratio is expected to increase the risk
of sperm competition and thus sperm traits affecting siring success can differ
amongst populations. Here we test the hypothesis that high male-female ratios
will enhance sperm competitiveness of Rana temporaria males. In this
species, local populations can show either prolonged or explosive breeding. In
a context of sperm competition and in controlled laboratory conditions,
prolonged-breeding males sired a higher proportion of eggs than
explosive-breeding males, regardless of female origin. This study demonstrates intrapopulation
variation in siring success under a situation of sperm competition, consistent
with the prolonged-explosive dichotomy of breeding strategies.Alvarez D, Viesca L & Nicieza AG (2013) Sperm competitiveness ...
Posted Nov 28, 2013, 3:33 AM by David Alvarez
New publication: Climate Influences Fledgling Sex Ratio and Sex-Specific Dispersal in a SeabirdClimate influences the dynamics of natural populations by direct effects over habitat quality but also modulating the phenotypic responses of organisms’ life-history traits. These responses may be different in males and females, particularly in dimorphic species, due to sex-specific requirements or constraints. Here, in a coastal seabird, the European shag (Phalacrocorax aristotelis), we studied the influence of climate (North Atlantic Oscillation, NAO; Sea Surface Temperature, SST) on two sex-related population parameters: fledgling sex ratio and sex-specific dispersal. We found that fledgling sex ratio was female skewed in NAO-positive years and male skewed in NAO-negative years. Accordingly, females dispersed a longer distance in NAO-positive years when females were overproduced, and on the contrary, males ...
Posted Nov 28, 2013, 1:44 AM by David Alvarez