Exploring adaptation in the introduced house sparrow to Australian climates and environments

Invasive species have always been excellent models for understanding local adaptation through their colonization of new and varied environments. The house sparrow (Passer domesticus) has been a key model invasive species around the world and in this thesis, I have expanded this research to consider the Australian population across the current distribution over eastern Australia. Given that we believe most sparrows were introduced to Australia from England in the 1860’s they have colonized temperate biomes that are like their home range and very different climates in the tropical and arid biomes. I have found that genetic differentiation across this region is relatively strong, and this population structure over a range of climates can allow independent populations to adapt to local climates, over the past 150 years. In line with this idea I have found evidence of significant differentiation in morphology across climatic gradients, in this species. In another passerine species, I demonstrated that this is likely largely explained by phenotypic plasticity. Additionally, using genomic SNP data and genome scan methods I explored links between differentiation in allele frequencies and climatic variation across populations. These models found many significant outlier loci, some of which were linked to genes on the reference genome relating to traits important to local adaptation, such as thermal tolerance, immune function and morphology. In addition to exploring climate as a selective force I consider the effects of heavy metal pollution on urban sparrow populations and found outlier genes that could be relevant to responding to lead contamination. These functional loci provide targets for future research describing the mechanisms behind local adaptation. Understanding how species adapt to different environmental conditions through both phenotypic plasticity and selection will be important for predicting the response of wildlife to the rapid changes in habitat and climate caused by humans -- Abstract.