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Deakin University (2019)

Great bowerbirds as ecosystem engineers in a semi-arid savannah community

Hodgson, Jessica

Titre : Great bowerbirds as ecosystem engineers in a semi-arid savannah community

Auteur : Hodgson, Jessica

Université de soutenance : Deakin University

Grade : Doctor of Philosophy (PhD) 2019

Sommaire
This thesis logically follows from my previous research. Previously, I discovered that when great bowerbird (Ptilonorhynchus nuchalis) males display the fruits of a burdekin plum (Pleiogynium timorense) to females in their sexual display they are more likely to achieve a mating from that female. The male receives a fitness benefit in the form of a mating advantage simply from using this fruit.
In the research presented in this thesis, I asked the next logical question : does the burdekin plum also receive a fitness benefit from being transported and used by the male great bowerbird ? The research also addresses the general question of whether or not there is a mutualistic interaction between Great bowerbirds and burdekin plum plants.
I investigated the importance of the male bowerbird in dispersing the burdekin plum fruits in semi-arid savannah, how abandoned and decomposing bowers influence soil properties and critical resources, and whether burdekin plum seedlings benefitted from increased probability of survival and enhanced growth rates at microhabitats (shrubs) with an abandoned bower or no bower. In addition, I expanded my research to explore how the bowerbird may be affecting other species in the community such as the soil microbial and local plant communities.
My results indicate that, in the dry savannah found in my study area, burdekin plum seeds depend on dispersal to protected microhabitats of shrubs in order to establish and simply do not reach them without the directed dispersal to ideal microhabitats provided by the bowerbird. Furthermore, great bowerbird males can be considered ecosystem engineers because they modify the availability of resources to other species thus affecting the distribution of burdekin plums (Chapter 3), soil microbes (Chapter 4) and other plants (Chapter 5). Ecosystems engineers are important for generating landscape heterogeneity, species richness and maintaining ecosystem function by creating or modifying habitat in such a way that allows species not normally found there to survive and reproduce. This mutualistic relationship could have significant consequences for the burdekin plum and the great bowerbird such as coevolution and the degree of both species’ susceptibility to environmental change. Moreover, the significant impact of the great bowerbirds’ bower building behaviour could have significant impacts on the wider plant community and our understanding of applying species interactions to facilitate land management and restoration in semi-arid woodland savannah.

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