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Laiolo P.,Research Unit of Biodiversity CSIC UO PA
Ethology Ecology and Evolution | Year: 2011

One of the clearest examples of animal adaptation to urban habitats is the variation in their vocalisations driven by anthropogenic noise. A behavioural process that has received less attention in urban habitats is how anthropogenic barriers influence animal spacing behaviour and communication. I addressed the effects of the distribution of bird territories in urban habitats and the pattern of song differentiation over distance among neighbouring birds. I studied natural and suburban populations of the white-crowned sparrow Zonotrichia capensis in Argentina. This songbird dwells in gardens, but is here less abundant and more regularly spaced than in open woodlands. Neighbouring birds in garden suburbs sang songs that were more similar to each other than neighbouring birds in natural habitats. Song differentiation was greater within natural habitats than within suburbs at distance 400 m. At larger distances differences among habitats were no longer significant. Neighbour songs were more homogeneous where territories were more regularly spaced, considering all habitats or urban ones only. Selection for individual recognition of neighbours through songs and greater male-male interactions could have enhanced acoustic differentiation in natural habitats. Conversely, weak territorial interactions in suburbs with abundant landmarks may have constrained song output, resulting in song homogenisation. This study points to differences in variability that may be more difficult to detect than differences in acoustic properties per se, and suggests that the effects of urbanisation on animal communication can be underestimated if inter-individual variation is not properly addressed © 2011 Dipartimento di Biologia Evoluzionistica dell?Università, Firenze, Italia.

Dahl E.,Uppsala University | Orizaola G.,Uppsala University | Nicieza A.G.,University of Oviedo | Nicieza A.G.,Research Unit of Biodiversity CSIC UO PA | Laurila A.,Uppsala University
Journal of Animal Ecology | Year: 2012

1. As size is tightly associated with fitness, compensatory strategies for growth loss can be vital for restoring individual fitness. However, immediate and delayed costs of compensatory responses may prevent their generalization, and the optimal strategy may depend on environmental conditions. Compensatory responses may be particularly important in high-latitude habitats with short growing seasons, and thus, high-latitude organisms might be more efficient at compensating after periods of unfavourable growth conditions than low-latitude organisms. 2. We investigated geographical differences in catch-up growth strategies of populations of the common frog (Rana temporaria) from southern and northern Sweden in two factorial common garden experiments involving predation risk and two different causes of growth arrest (nutritional stress and low temperatures) to evaluate how the compensatory strategies can be affected by context-dependent costs of compensation. Larval and metamorphic traits, and post-metamorphic performance were used as response variables. 3. Only northern tadpoles exposed to low food completely caught up in terms of metamorphic size, mainly by extending the larval period. Low food decreased survival and post-metamorphic jumping performance in southern, but not in northern tadpoles, suggesting that northern tadpoles have a better ability to compensate after periods of restricted food. 4. Both northern and southern tadpoles were able to metamorphose at the same size as control tadpoles after being exposed to low temperatures, indicating that consequences of variation in temperature and food availability differed for tadpoles. However, the combination of low temperatures and predation risk reduced survival in both southern and northern tadpoles. Also, predation risk decreased energy storage in both experiments. 5. Our results highlight the influence of climatic variation and the type of stressor as selective factors shaping compensatory strategies. © 2012 British Ecological Society.

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