Fire influences ant diversity by modifying vegetation structure in an Australian tropical savanna

François Brassard, Magen J. Pettit, Brett P. Murphy, Alan N. Andersen

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Abstract

Fire is a dominant ecological force shaping many faunal communities globally. Fire affects fauna either directly, such as by killing individuals, or indirectly, such as by modifying vegetation structure. Vegetation structure itself also modulates fire frequency and intensity. As such, faunal responses to fire need to be seen through the lens of variable fire activity and vegetation structure. Here, we incorporate information on fire activity and vegetation structure to enhance an understanding of the response of ants to long-term (17-year) experimental fire treatments in an extremely fire-prone tropical savanna in northern Australia. Previous analysis revealed limited divergence in ant communities after 5 years of experimental fire treatment. Hence, we first investigated the extent to which ant communities diverged over a subsequent 12 years of treatment. We then assessed the relative contribution of fire treatment, cumulative fire intensity (fire activity), and woody cover to responses of ant species frequency of occurrence, richness, and composition. We found that, even after 17 years, fire treatments explained little variation in any ant response variable. In contrast, woody cover was a strong predictor for all of them, while fire activity was a moderate predictor for abundance and richness. Ant species occurrence and richness increased in open habitats receiving higher levels of fire activity, compared with plots with higher vegetation cover experiencing low (or no) fire activity. Moreover, species composition differed between plots with high and low vegetation cover. Our findings provide experimental support to the principle that the effects of fire on fauna are primarily indirect, via its effect on vegetation structure. Furthermore, our results show that a “uniform” fire regime does not have uniform impacts on the ant fauna, because of variability imposed by interactions between vegetation structure and fire activity. This helps to explain why there is often a weak relationship between pyrodiversity and biodiversity, and it lessens the need for active management of pyrodiversity to maintain biodiversity.

Original languageEnglish
Article numbere4143
Pages (from-to)1-15
Number of pages15
JournalEcology
Volume104
Issue number9
DOIs
Publication statusPublished - Sept 2023

Bibliographical note

Funding Information:
We acknowledge that our work was conducted on the traditional lands of the Kungarakany and Larrakia nations. The establishment and maintenance of the Territory Wildlife Park experiment were funded by CSIRO, Charles Darwin University, the Bushfire Cooperative Research Centre and the Northern Territory Government. François Brassard was supported by a University Research Training Scheme, a Research Training Program Stipend Scholarship, and a Holsworth wildlife research endowment grant. Brett Murphy was supported by a fellowship from the Australian Research Council (FT170100004). We thank our data contributors John Morgan, Shaun Levick and Jon Schatz. We thank Benjamin Aidoo, Paris O'Rourke, Kyle Glover, Aliesha Jane Hvala and Taz, Megan L. Taylor, Rebecca Burrie, Kinjia May Munkara-Murray, Vanessa Solano and Jenny House for their help with fieldwork, and Tanvi Patel, Benjamin Aidoo, Paris O'Rourke, Kyle Glover, Rebecca Burrie and Vamshidhar Reddy for their assistance in the laboratory. Finally, we are most grateful to the staff of the Territory Wildlife Park for their ongoing support for the experiment. Open access publishing facilitated by Charles Darwin University, as part of the Wiley - Charles Darwin University agreement via the Council of Australian University Librarians.

Funding Information:
We acknowledge that our work was conducted on the traditional lands of the Kungarakany and Larrakia nations. The establishment and maintenance of the Territory Wildlife Park experiment were funded by CSIRO, Charles Darwin University, the Bushfire Cooperative Research Centre and the Northern Territory Government. François Brassard was supported by a University Research Training Scheme, a Research Training Program Stipend Scholarship, and a Holsworth wildlife research endowment grant. Brett Murphy was supported by a fellowship from the Australian Research Council (FT170100004). We thank our data contributors John Morgan, Shaun Levick and Jon Schatz. We thank Benjamin Aidoo, Paris O'Rourke, Kyle Glover, Aliesha Jane Hvala and Taz, Megan L. Taylor, Rebecca Burrie, Kinjia May Munkara‐Murray, Vanessa Solano and Jenny House for their help with fieldwork, and Tanvi Patel, Benjamin Aidoo, Paris O'Rourke, Kyle Glover, Rebecca Burrie and Vamshidhar Reddy for their assistance in the laboratory. Finally, we are most grateful to the staff of the Territory Wildlife Park for their ongoing support for the experiment. Open access publishing facilitated by Charles Darwin University, as part of the Wiley ‐ Charles Darwin University agreement via the Council of Australian University Librarians.

Publisher Copyright:
© 2023 The Authors. Ecology published by Wiley Periodicals LLC on behalf of The Ecological Society of America.

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