title: What makes species more vulnerable to environmental change? Passerines as a case study
Creators: name: Salido Grana, Lara
Publisher: name: University of Liverpool Repository
Year: 2014

description: Environmental change presents the greatest challenges to biodiversity conservation. From climate changes to land cover conversion and pollution effects, global biodiversity faces many threats. Though conservation actions have been put into place to halt the loss of biodiversity, recent studies suggest that conservation actions have largely failed to do this. Hence, understanding the links between species responses, environmental pressures and the role of species characteristics in conferring resilience to these environmental pressures would be fundamental to develop adequate conservation measures. This thesis focuses on a range of approaches to investigate the impacts of well-known environmental pressures on the passerine community in the UK to try to uncover mechanisms underpinning species responses to environmental change. Furthermore, considering that bird species are currently been used as biodiversity indicators, it would be of great use to identify new venues to measure and monitor species responses to environmental change that would help improve the current set of indicators. Examining multiple pressures within the same analytical framework was valuable for demonstrating that land cover and pollution drivers are of equivalent importance to climate in structuring bird communities at a broad scale in the UK. Both community and niche studies revealed that winter conditions and pollution were key in structuring passerine communities together with pollution at this broad scale. In terms of colonisation and extinction processes the spatial structure of the species occupancy appeared to have a dominant role in driving the observed dynamics as well as again, climate change in terms of warming winter temperatures. Throughout this thesis, the above mentioned ecological responses were linked to species ecological traits with the aim of gaining a greater understanding of the mechanisms underpinning species’ differential responses to environmental change and identifying those trait groups that may be most vulnerable or most valuable as indicators. A significant group of characteristics that consistently appeared to be linked to species resilience to observed environmental pressures (particularly climate change) was phenological traits. Species with earlier laying dates and/or longer laying periods were associated with increasing population trends, larger colonisation rates and smaller extinction rates. Also analysis of species niches in relation to environmental pressures not only revealed the dynamic nature of niche parameters, confirming niche evolution and niche tracking in some species but also confirmed their relationship with both species characteristics and current conservation categories. Finally this study reiterated the fact that relationships between species characteristics and environmental pressures involve complex interactions that significantly affect and transform species responses to environmental pressures. For example the interaction between migratory behaviour and phenological traits (i.e. earlier laying dates and longer laying periods) meant that migrant species were less likely to have declining populations or that warming winter temperatures were associated with increased colonisation for migrants or species with more annual broods were less likely to show extinction in cells with temperature increase. All these results not only confirm the suitability of birds and particularly passerine species as indicators of environmental use and their potential and importance as part of indices and monitoring programmes but also highlights the importance of updating the next generation of indicators with measurements that can take into account important species characteristics associated with resilience to environmental pressures (i.e. phenological traits).