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Influencia diferencial de la expresión de Slc7a11 y la condición corporal sobre la pigmentación producida por feomelanina en dos poblaciones de trepador azul Sitta europea con diferente riesgo de depredación

The expression of the gene Slc7a11 promotes the antioxidant capacity of cells by providing them with cysteine that can be used for the synthesis of glutathione (GSH), the most important intracellular antioxidant. In melanocytes, intracellular cysteine can also enter melanosomes and get incorporated in the pigment pheomelanin synthesis pathway, thus decreasing cysteine availability for GSH synthesis and potentially creating chronic oxidative stress. Therefore, this study hypothesized that a mechanism limiting the use of intramelanocytic cysteine for pheomelanin synthesis in environmental conditions generating oxidative stress may be physiologically advantageous and favored by natural selection. Evidence we searched of such a mechanism by comparing the influence of melanocytic Slc7a11 expression on pheomelanin?based pigmentation in developing Eurasian nuthatch Sitta europaea nestlings from two populations differing in predation risk, a natural source of oxidative stress. Pheomelanin synthesis and pigmentation tended to increase with Slc7a11 expression in the low?risk population as expected from the activity of this gene, but decreased with Slc7a11 expression in the high?risk population. The same was not observed in the expression of five other genes influencing pheomelanin synthesis without affecting cysteine availability in melanocytes. The influence of body condition on the intensity of pheomelanin?based pigmentation also differed between populations, being positive in the low?risk population and negative in the high?risk population. The resulting pigmentation of birds was more intense in the high?risk population. These findings suggest that birds perceiving high predation risk may limit the use of cysteine for pheomelanin synthesis, which becomes independent of Slc7a11 expression. Some birds may have thus evolved the ability to adjust their pigmentation phenotype to environmental stress. informacion[at] Galván & Sanz (2020) Differential influence of Slc7a11 expression and body condition on pheomelanin-based pigmentation in two Eurasian nuthatch Sitta europaea populations with different predation risk. J Avian Biol DOI 10.1111/jav.02275
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Humans and scavenging raptors facilitate Argentine ant invasion in Doñana National Park

Humans and scavenging raptors facilitate Argentine ant invasion in Doñana National Park

Biotic resistance by native communities could have a role in the spread of invasive species. Native communities with higher species richness should be less susceptible to invasion by exotic species than those with fewer component species, interspecific interactions acting as biotic barriers by creating a highly competitive environment. This seems to be the case in the invasion of the Argentine ant, Linepithema humile, but only when the environment is unfavorable for the survival of the invader. The progress of Argentine ant invasion through favorable and unfavorable habitats of Doñana National Park was studied across three temporal snapshots covering three decades (1992, 2000, 2016). Biotic resistance of the native community was assessed using species richness, as well as dominance and community structure. The role of abiotic factors (quality of surrounding habitat and spatial variables) and of potential vectors of Argentine ant dispersal across unfavorable areas was also explored. No evidence of biotic resistance was found. On the contrary, invasion proceeded from trees with higher ant species richness, probably because those trees are larger and provide more resources and better protection from aridity. Furthermore, evidence was found that the invasion of new trees across a matrix of unfavorable habitat could be influenced not only by humans, but also by scavenging avian predators, which could act as vectors of ant dispersal through transport of carrion also exploited by the ants. Such leapfrog expansion through mobile predators could represent an overlooked mechanism that would enrich our understanding of invasion dynamics and provide potential opportunities for management of invasive species. informacion[at] Castro-Cobo et al (2019) Humans and scavenging raptors facilitate Argentine ant invasion in Doñana National Park: no counter-effect of biotic resistance. Biol Invasions 21:2221–2232. Doi 10.1007/s10530-019-01971-5