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San Sebastián de los Reyes, Spain

Edelaar P.,Uppsala University | Edelaar P.,CSIC - Donana Biological Station | Alonso D.,Aranzadi Ringing Scheme | Lagerveld S.,Leiden University | And 2 more authors.
Journal of Evolutionary Biology | Year: 2012

Divergent selection stemming from environmental variation may induce local adaptation and ecological speciation whereas gene flow might have a homogenizing effect. Gene flow among populations using different environments can be reduced by geographical distance (isolation-by-distance) or by divergent selection stemming from resource use (isolation-by-ecology). We tested for and encountered phenotypic and genetic divergence among Spanish crossbills utilizing different species of co-occurring pine trees as their food resource. Morphological, vocal and mtDNA divergence were not correlated with geographical distance, but they were correlated with differences in resource use. Resource diversity has now been found to repeatedly predict crossbill diversity. However, when resource use is not 100% differentiated, additional characters (morphological, vocal, genetic) must be used to uncover and validate hidden population structure. In general, this confirms that ecology drives adaptive divergence and limits neutral gene flow as the first steps towards ecological speciation, unprevented by a high potential for gene flow. © 2012 The Authors. Journal of Evolutionary Biology © 2012 European Society For Evolutionary Biology. Source


Bjorklund M.,Uppsala University | Alonso D.,Aranzadi Ringing Scheme | Edelaar P.,Uppsala University | Edelaar P.,Pablo De Olavide University | Edelaar P.,CSIC - Donana Biological Station
Biological Journal of the Linnean Society | Year: 2013

Conservatism of ecological niches can cause geographical ranges or the formation of new species to be constrained, and might be expected in situations where strong trade-offs result in ecological specialization. Here we address the flexibility of resource use in European crossbills by comparing the ecological and genetic similarities between four Mediterranean and three northern European crossbill populations, all specialized in feeding on a different resource. We used sequence data of one mitochondrial and two nuclear genes from between 211 and 256 individuals. The northern crossbills were genetically too similar to infer which population was more related to the southern ones. Crossbills from the island of Mallorca showed genetic signatures of a stable and isolated population, supporting their past treatment as a locally (co)evolving taxon, and seem to have evolved from an ecologically distinct ancestor. Previous studies in other populations also suggest that genetic similarity does not predict morphological and resource similarity. We estimate that the divergence of all western European crossbills has occurred within the last 11000 years. Overall, it appears that crossbills can diversify rapidly and with little niche conservatism, but that such potentially reproductively isolated specialists are evolutionarily short-lived. © 2013 The Linnean Society of London. Source


Arizaga J.,Institute of Avian Research Vogelwarte Helgoland | Dean J.I.,Gorosti Natural science Society | Vilches A.,Aranzadi Ringing Scheme | Vilches A.,University of Navarra | And 2 more authors.
Bird Study | Year: 2011

Capsule: Counting and mist-netting provided different estimates of abundance. Aims: To compare the efficiency, constraint and bias of mist-netting versus line transects for the estimation of species richness and abundance of passerines. Methods: Mist-nets (126 linear metres) placed crossing a 420m-long hedgerow line, open for four hours starting at dawn, four days per month from June 2006 to May 2007. During this same period, we conducted a transect parallel to a 1.3-km hedgerow line, four times per month. Results: Estimation of species richness did not vary between methods, even when controlling for ecological groups, whereas the abundance estimations did vary. Conclusions: Overall, line transects are better than mist-netting for estimating species richness and abundance since they are less costly, less invasive, and less time-consuming. However, if fine ecological analyses are required, including species abundance, mist-netting is preferred for solitary passerines that feed on insects and forage in the foliage, and line transects are better for gregarious passerines that feed on seeds or forage on the ground. © 2011 British Trust for Ornithology. Source


Alonso D.,Aranzadi Ringing Scheme | Arizaga J.,Aranzadi Ringing Scheme
Ringing and Migration | Year: 2011

The aim of this study was to investigate the relationship between breeding, moulting and fuel load of Common Crossbills Loxia curvirostra curvirostra inhabiting a Scots pine Pyrenean forest. Data were collected from two locations (Sierra de Uztarroz and Bigüezal) in northern Iberia by systematic mist netting between 2000 and 2008. Breeding females were detected in most months of the year except June, October and November, and with two main peaks, one in late winter (March), and another in the summer (August). Between years, reproduction was more variable in some months than in others, particularly in summer months. This suggests that breeding during the summer was more likely to be influenced by external factors and relatively opportunistic compared to winter breeding. Moulting adults of both sexes were captured during almost every month with a unimodal pattern peaking in June, similar to the pattern described for Mediterranean Crossbills. Moulting did not overlap with breeding, and our data do not support suspended moult patterns. Mean fat scores overall were low and, as was the case for body mass, showed little month-to-month variation. © 2011 British Trust for Ornithology. Source


Arizaga J.,Aranzadi Ringing Scheme | Arizaga J.,Institute of Avian Research Vogelwarte Helgoland | Alonso D.,Aranzadi Ringing Scheme | Barba E.,University of Valencia
Ringing and Migration | Year: 2010

The aim of this study was to analyse the patterns of migration and wintering of European Robins Erithacus rubecula in northern Iberia (Plaiaundi Ecological Park, Irún, N Spain). Overall, 185 Robins were ringed at weekly trapping sessions from September 2004 to April 2005. The temporal distribution of abundance and recaptures indicated that the autumn migration period lasted from September to November, the winter period from November to February, and the spring migration from March to April. Some wintering Robins arrived earlier than most of the migrants which passed through the area in autumn, whilst most left the area before the majority of spring migrants appeared. First-winter Robins were always more abundant than older birds, and females more abundant than males. Morphological traits varied only in relation to sex, and it was not possible to distinguish between migrating and wintering Robins from measurements. Overall, body mass and fuel load were low during both the autumn and spring migrations, supporting the idea that Robins passing through northern Iberia migrated in short steps. In winter, however, higher values of body mass (but not of fat scores) were observed. © 2010 British Trust for Ornithology. Source

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