RESEARCH

Related publications

- Velando A, Álvarez D & Oro D (2018) Complex demographic heterogeneity from antropogenic impacts in a coastal marine predator. Ecology Applications (en prensa)

- Genovart M, Arcos JM, Álvarez D, McMinn M, Meier R, Wynn R, Guilford T & Oro D. (2016) Demography of the critically endangered Balearic shearwater: impact of fisheries and time to extinction. Journal of Applied Ecology. doi: 10.1111/1365-2664.12622

- Álvarez D (2015) Análisis de la mortalidad de las poblaciones de cormorán moñudo (Phalacrocorax aristotelis) en artes de pesca en la Demarcación Marina Noratlántica. Aplicación 23.06.456D.640. Ministerio de Agricultura, Alimentación y Medio Ambiente (MAGRAMA).

- Barros, A, Álvarez D, Velando A (2014) Long-term reproductive impairment in a seabird after the Prestige oil spill. Biology Letters. doi: 10.1098/rspb.2013.1041

- Barros, A, Álvarez D, Velando A (2013) Climate Influences Fledgling Sex Ratio and Sex-Specific Dispersal in a Seabird. PLoS ONE 8(8): e71358.

- Álvarez D & Pajuelo MAF (2011). Southern populations of European shag are laying eggs earlier in response to local weather conditions but not to large-scale climate. Ardeola 58: 239-250.

- Velando A, Álvarez D, Mouriño J, Arcos F & Barros A (2005) Population trends and reproductive success of European Shag following the Prestige oil spill in the Iberian Peninsula. Journal of Ornithology 146: 116-120

Genetic structure and dispersion models in subdivided populations

The spatial genetic structure of some species is strongly conditioned by their habitat characteristics. In some cases, this habitat is discontinuous and thus it might match an island model of population structure. We are using molecular markers (DNA microsatellites) and mitocondrial RNA to examine spatial patterns of genetic differentiation and genetic diversity in fish (Salmo trutta), anurans (Rana temporaria and Salamandra salamandra) and also with seabirds (Phalacrocorax aristotelis). In Brown trout (Salmo truta), our preliminary results suggest a model of unidirectional (downstream) dispersion associated with natural barriers preventing upstream migration.

The spatial genetic structure of the common frog (Rana temporaria) is strongly conditioned by the dependence to the discontinuous aquatic habitat, and thus it might match an island model of population structure. Our preliminary results did not support the hypothesis of genetic differentiation consistent with a hierarchic spatial pattern, but this can be the result of a lack of resolution due to a low number of markers. We evidenced a pattern of isolation by distance at large and very small scales but not at intermediate distances. Despite overall all these results are strictly preliminary, our data reveal that differentiation of Rana temporaria population in mountain areas can occur at a very fine spatial scale.

We used nuclear microsatellite and mitochondrial DNA markers to quantify population genetic structure and variation across 20 populations of European Shag (Phalacrocorax aristotelis), spanning a large geographical range. Despite high breeding philopatry, rare cross-sea movements and recognised subspecies, population genetic structure was weak across both microsatellites and mitochondrial markers. Furthermore, although isolation by distance was detected, microsatellite variation provided no evidence that open sea formed a complete barrier to effective dispersal.

Related publications

Fernández-Chacón A, Genovart M, Álvarez D, Cano JM, Ojanguren AF, Rodríguez-Muñoz R & Nicieza AG. (2015) Neighbouring populations, opposite dynamics: survival and growth patterns of brown trout (Salmo trutta) in mountain streams. Oecologia 178: 379-389.

- Barlow EJ, Daunt F, Wanless S, Álvarez D, Reid JM & Cavers S (2011). Weak global population genetic structure in a philopatric seabird, the European shag (Phalacrocorax aristotelis). Ibis 153: 768-778.

- Nicieza AG, Choda M & Álvarez D (2010) Estructura genética de poblaciones subdivididas: Identificación de unidades de conservación de anfibios en la Cordillera Cantábrica. En: Diego, F.J.; Bosch, J.; Ayllón, E.; Hernández, P.L.; Sevilla, L. & Mora, A. (Eds.) Anfibios y Reptiles del Parque Nacional de Picos de Europa. Colección Naturaleza y Parques Nacionales. Serie Técnica. Ministerio de Medio Ambiente, Medio Rural y Marino. pp189-202.

Study of compensatory growth and their associated costs

Compensatory growth is a phase of unusually rapid growth following a period of growth depression. This response allows to animals to achieve the same size-for-age as continuously fed contemporaries. This ability to catch up in size indicates that normal growth rates are less than the maximum possible and suggests that there are costs associated with rapid growth rates, such that there is a trade-off between the benefits of a large body size and the costs of achieving it.

During the last years I worked with Alfredo G. Nicieza in some experiments about compensatory growth in Brown trout (Salmo trutta) in natural and artificial conditions. Our results did not support the the common view that compensatory growth be a general response to growth depression, and we sugested that compensation in other salmonids could be related to size-thresholds associated with developmental switches as the onset of sexual maturation and migration.

In colaboration with Neil B. Metcalfe, in Glasgow University I studied the medium and long term effects of rapid growth in three-spined Sticklebacks (Gasterosteous aculeatus), both in the swimming efficiency of animals with higher growth rates and in the effects of rapid growth on reproductive behaviour.

I am also interested in the practical aspects of compensatory growth analysis. In some cases the incorrect selection of size dimensions, growth descriptors, or the analytical tools used can produce a false detection of the CG. Due to this, it is very important to find the correct way to analyse the data in order to obtain trustworthy conclusions.

Related publications

- Nicieza AG & Álvarez D (2009) Statistical analysis of structural compensatory growth: how can we reduce the rate of false detection?. Oecologia 159: 27-39.

- Álvarez D & Metcalfe NB (2007) The trade-off between catch-up growth and escape speed: variation between habitats in the cost of compensation. Oikos 116: 1144-1151.

- Álvarez D & Metcalfe NB (2005) Catch-up growth and swimming performance in sticklebacks (Gasterosteous aculeatus): seasonal changes in the cost of compensation. Canadian Journal of Fisheries and Aquatic Sciences 62: 2169-2173

- Álvarez D & Nicieza AG (2005) Compensatory response 'defends' energy levels but not growth trajectories in brown trout, Salmo trutta L. Proceedings of the Royal Society Series B 272: 601-607

Evolution of antipredator defenses

Predation is one of the most important causes of mortality in pre-reproductive stages. Because a large part of that mortality takes place early in life and the risk of predation often decreases with increasing body size, there must be strong selective pressures for the early development of antipredator defences. During the last years we have used anuran larvae and juvenile fish to study the role of behaviour and morphology in predator avoidance and how these defenses can be induced in the presence of non-letal predators.

Related publications

- Álvarez D & Nicieza AG (2009) Differential success of prey escaping predators: tadpole vulnerability or predator selection. Copeia 2009: 453-457.

- Álvarez D & Bell AM (2007) Sticklebacks from streams are more bold than sticklebacks from ponds. Behavioural Processes 76: 215-217.

- Nicieza AG, Álvarez D & Atienza ES (2006) Delayed effects of larval predation risk and food quality on anuran juvenile preformance. Journal of Evolutionary Biology 19: 1902-1103.

- Álvarez D & Nicieza AG (2003) Predator avoidance behaviour in wild and hatchery-reared trout: the role of experience and domestication. Journal of Fish Biology 63: 1565-1577

Evolution of mating systems

In previous studies we have proved that anuran amphibians show high reproductive plasticity depending, above all, of the environmental conditions experienced. During the last 5 years we have studied the population dynamics of the Common frog (Rana temporaria) and Common toad (Bufo bufo) in mountain and lowland areas, and we have observed that the reproductive strategies were completely different in both areas (explosive and prolonged breeding, respectively). During the following years I will try study the evolution of mating systems and their population implications from an intraspecific point of view.

I am also interested in the evolutionary implications of sexual conflict, sperm competition and the role of MHC (Major histocompatibility complex) in mate choice. Actually I am doing some experiments aimed to study if the interespecific hybridization could be mediated by the MHC.

Related publications

- Álvarez D, Viesca L & Nicieza AG (2014) Sperm competitiveness differs between two frog populations with different breeding systems. Journal of Zoology 292: 202-205.

Causes and effects of interspecific hybridization in natural populations

The Spanish populations of Atlantic salmon have suffered a very important decline throughout the XXth century, in fact, in some regions like Galicia the species is in danger of extinction (Hervella & Caballero 2001). If genetic introgression is possible, such that hybrids can reproduce in the wild and their offspring are viable and fertile, the transference of genes towards one of the species will increase their genetic variability (increase in intraspecific variation) and at the same time the differences between the species will be reduced (decrease of interspecific variation). In the Iberian Atlantic salmon populations, females which accept male trout as mates will therefore lose in the short term their great energy investment in gamete production, which will not go on to the population gene pool beyond the second generation. A mating strategy that results in hybridization should therefore have become extinct through natural selection; nevertheless, it is evident that it has not been eliminated in the wild, since there are hybrids throughout the area of sympatry of the species. In small populations with sex-ratio clearly biased towards the females, the probability that a female over mature due to the absence of a conspecific anadromous male in considerable. The female that accept a male trout as a mate will obtain an offspring with high proportion of salmon, whereas the female that does not accept any male will lose the totality of his eggs.