Date of Award

Spring 1-1-2017

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Ecology & Evolutionary Biology

First Advisor

Kendi F. Davies

Second Advisor

Brett A. Melbourne

Third Advisor

Sharon K. Collinge

Abstract

A crucial ecological question for the twenty-first century is how organisms will respond to the threat of habitat fragmentation. My dissertation is focused on determining the impacts of long-term experimental habitat fragmentation on ant communities in southeastern Australia. I use ants as a model organism because they play a crucial ecological role in Australian environments. My research was conducted at the Wog Wog Long-term Habitat Fragmentation Experiment in New South Wales, Australia.

First, I follow two ant species through 21 years of fragmentation to determine how their responses changes over time. I found that Leptomyrmex erythrocephalus was not affected by fragmentation in the short term, but 21 years after fragmentation, it was less likely to occur in mature pine matrix and fragments than in continuous forest controls. Aphaenogaster longiceps was equally likely to occur in the fragments, controls and pine matrix early in the experiment but by year 21 post-fragmentation was less likely to occur in the pine matrix than fragments or controls. I conclude that changes in matrix suitability and specific habitat characteristics influence ant persistence in Eucalyptus fragments.

Next, I determine the relative importance of dispersal and selection by the environment for ant communities in which the spatial context of communities has been altered by experimental habitat fragmentation, compared to unaltered controls. I show that fragmentation increased the role of dispersal in the assembly of communities in small and medium fragments, while at the same time increasing the role of selection in the assembly of communities in large fragments. I demonstrate that the processes that determine community assembly are altered when the spatial context of a community changes.

Finally, I determine the impacts of habitat fragmentation on ant-mediated seed removal. Fragmentation increased the rate of seed removal in large fragments and fragment cores by changing the environment. Fragmentation reduced the number of seeds removed per ant in small fragments by reducing temperature and increased the number of seeds removed per ant in medium and large fragments by reducing grass coverage. This study shows that fragmentation can alter seed removal through changes to the environment that alter ant behavior.

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