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Argentine ants harm nestlings of the blue tit

The consequences of ant invasions on ecosystems may only become apparent after long periods. In addition, predicting how sensitive native fauna will respond is only possible if the underlying proximate mechanisms of their impact are identified. The attraction of the native and invasive ant community to artificial bird nests was studied, together with reproduction of a wild native songbird over five consecutive breeding seasons in relation to the presence of an invasive ant species. Biometric, reproductive and individual blood parameters of great tits Parus major breeding in invaded as compared to uninvaded sites by Argentine ants Linepithema humile were analysed. Great tits bred preferably in uninvaded territories by the Argentine ant. Moreover, Argentine ants were more abundant at nests in invaded sites, than any native ant species were at uninvaded sites. Further, Argentine ants recruited at the artificial nests more intensively and responded to a larger variety of nest (intact eggs, cracked eggs, faeces, and cracked eggs plus faeces) contents than native species. Although breeding success and adult condition did not vary in relation to invasion status, offspring quality was negatively affected by the presence of Argentine ants. Nestlings reared in invaded sites were lighter, with lower wing/tarsus length ratio and had a reduced nutritional condition and altered oxidative stress balance as measured from several blood parameters. The interspersed distribution and small distance between invaded versus uninvaded territories suggest that ant presence affects nestling condition through direct interference at the nest. These results highlight the importance of evaluating the proximate effects like physiological parameters of the native fauna, when studying invasive ant-native bird interactions. informacion[at] Álvarez et al (2020) Breeding consequences for a songbird nesting in Argentine ant' invaded land. Biol Invasions
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Vitamin E supplementation—but not induced oxidative stress—influences telomere dynamics during early development in wild passerines

Vitamin E supplementation—but not induced oxidative stress—influences telomere dynamics during early development in wild passerines

Telomere length is a marker of cellular senescence that relates to different components of individual fitness. Oxidative stress is often claimed as a main proximate factor contributing to telomere attrition, although the importance of this factor in vivo has recently been challenged. Early development represents an ideal scenario to address this hypothesis because it is characterized by the highest rates of telomere attrition of the life and by an arguably high susceptibility to oxidative stress. The effect of oxidative stress on telomere dynamics during early development was tested by exposing pied flycatcher nestlings Ficedula hypoleuca to either an oxidative challenge (diquat injections), an antioxidant (vitamin E) or control treatments (PBS injections and supplementation with vehicle substance). No effects of treatments were found on average telomere change during the nestling period. However, vitamin E supplementation, which increased growth, removed the association between initial telomere length and telomere attrition. Diquat-treated nestlings, by contrast, showed no differences in growth or telomere dynamics with respect to controls. These results do not support the hypothesis that oxidative stress is the main direct mechanism explaining telomere attrition in vivo, and highlight the importance of micronutrient intake during early development on telomere dynamics. Studies addressing alternative action pathways of vitamins on growth and telomere dynamics, perhaps via restoration mechanisms, would provide important insights on the proximate factors affecting telomere attrition during this critical phase of life. informacion[at] Pérez-Rodríguez et al. (2019) Vitamin E supplementation—but not induced oxidative stress—influences telomere dynamics during early development in wild passerines. Front Ecol Evol