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Quantifying the Dietary Overlap of Two Co-Occurring Mammal Species Using DNA Metabarcoding to Assess Potential
Aurelie M Kanishka1, Christopher MacGregor1, Linda E Neaves1
1Fenner School of Environment and Society The Australian National University Canberra Australian Capital Territory Australia.
Ecology and Evolution
|April 14, 2025
Summary
Dietary overlap between possums and bush rats was high, suggesting competition. However, bush rats consumed a wider variety of food, potentially reducing competition and allowing coexistence.
Area of Science:
- Ecology
- Zoology
- Conservation Biology
Background:
- Interspecific competition is a key ecological process influencing species coexistence.
- Dietary overlap is a primary metric for assessing potential competition between co-occurring species.
- Research on competition among generalist species is less common than for specialists.
Purpose of the Study:
- To investigate the dietary overlap and potential for interspecific competition between two generalist species: the common brushtail possum (Trichosurus vulpecula) and the bush rat (Rattus fuscipes).
- To quantify the dietary range and similarity between these two species within a shared ecosystem.
Main Methods:
- Diet analysis using DNA metabarcoding on faecal samples.
- Identification and quantification of plant, fungal, and invertebrate DNA from faecal matter.
- Calculation of Pianka's overlap index to measure dietary similarity.
Main Results:
- High dietary similarity was found between possums and bush rats, with a Pianka's overlap index of 0.84.
- Bush rats exhibited a broad diet including plants, fungi, and invertebrates with low within-species variation.
- Common brushtail possums showed a more restricted diet, primarily consisting of plants.
Conclusions:
- Despite high apparent dietary overlap, fine-scale resource partitioning likely facilitates the coexistence of these generalist species.
- The broader dietary range of the bush rat may buffer it against competition from possums.
- Understanding niche partitioning is crucial for managing competition in ecosystems with generalist species.
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