BackgroundWhile the gene flow in some organisms is strongly affected by physical barriers and geographical distance, other highly mobile species are able to overcome such constraints. In southern South America, the Andes (here up to 6,900 m) may constitute a formidable barrier to dispersal. In addition, this region was affected by cycles of intercalating arid/moist periods during the Upper/Late Pleistocene and Holocene. These factors may have been crucial in driving the phylogeographic structure of the vertebrate fauna of the region. Here we test these hypotheses in the burrowing parrot Cyanoliseus patagonus (Aves, Psittaciformes) across its wide distributional range in Chile and Argentina.ResultsOur data show a Chilean origin for this species, with a single migration event across the Andes during the Upper/Late Pleistocene, which gave rise to all extant Argentinean mitochondrial lineages. Analyses suggest a complex population structure for burrowing parrots in Argentina, which includes a hybrid zone that has remained stable for several thousand years. Within this zone, introgression by expanding haplotypes has resulted in the evolution of an intermediate phenotype. Multivariate regressions show that present day climatic variables have a strong influence on the distribution of genetic heterogeneity, accounting for almost half of the variation in the data.ConclusionsHere we show how huge barriers like the Andes and the regional environmental conditions imposed constraints on the ability of a parrot species to colonise new habitats, affecting the way in which populations diverged and thus, genetic structure. When contact between divergent populations was re-established, a stable hybrid zone was formed, functioning as a channel for genetic exchange between populations.
Efecto de la edad y la localidad en la concentración de cadmio y cobre en el hígado de la gaviota dominicana Larus dominicanus Abstract.-We analyzed Cu and Cd liver concentration in adults and fledglings of Kelp gull from an urban (Coquimbo city) and a wild (Pájaros Islet) colony. Cu concentration was 15.57 ± 0.079 μg g -1 dry weight for adults and fledglings of both colonies. Adults Cd concentration from both colonies was 9.72 ± 0.110 μg g -1 dw, being 194% of the level considered toxic but in the range for seabirds. In the urban fledglings Cd was below the detection level. Wild fledgling showed higher concentration of 1.54 ± 0.064 μg g -1 dw which probably reflects a biomagnification process, because parents kleptoparasite and consume eggs and chicks of other seabirds.
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