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Trophic Change and Community Decline in Acrobat Ants After Rainforest Conversion to Cash Crops
Jessica Ehlers1, Tamara R Hartke1,2, Noah Janotta1
1Animal Ecology, J.-F. Blumenbach Institute of Zoology and Anthropology University of Göttingen Göttingen Germany.
Ecology and Evolution
|December 24, 2024
Summary
Tropical land-use change causes significant declines in acrobat ant (Crematogaster) density and diversity. Trophic strategies shift slightly, with reduced trophic diversity in monocultures impacting ecosystem functions.
Area of Science:
- Ecology
- Tropical Ecology
- Conservation Biology
Background:
- Tropical rainforest conversion to agriculture leads to biodiversity loss.
- Ants (Formicidae) are vital for ecosystem functioning, but their responses to land-use change are understudied.
- Acrobat ants (Crematogaster) are a key indicator group for tropical ecosystem health.
Purpose of the Study:
- To investigate the impact of land-use change on the density, diversity, and trophic strategies of Crematogaster ants.
- To compare ant communities across rainforest, jungle rubber, rubber monoculture, and oil palm monoculture systems.
- To understand how trophic niche adjustments in Crematogaster relate to land-use intensity.
Main Methods:
- Collected over 12,000 acrobat ants (14 species) via canopy fogging in Sumatra.
- Analyzed ant communities across four land-use systems: rainforest, jungle rubber, rubber, and oil palm.
- Utilized stable isotope analysis (carbon and nitrogen) to determine trophic positions and diversity.
Main Results:
- Significant declines in Crematogaster density, richness, and rarity were observed in rubber and oil palm monocultures compared to rainforest and jungle rubber.
- Trophic diversity, indicated by the range of stable nitrogen isotopes (Δ15N), was significantly reduced in monocultures.
- A shift towards more plant-based resources was suggested by lower δ13C values in monocultures, potentially influenced by the 'canopy effect'.
- Ant communities showed a nested subset structure, with oil palm supporting the fewest species, followed by rubber, jungle rubber, and rainforest.
Conclusions:
- Tropical land-use change drastically reduces Crematogaster ant density and diversity.
- Slight shifts in trophic structure occur, characterized by reduced trophic diversity in agricultural monocultures.
- These changes likely impair crucial ecosystem functions driven by Crematogaster ants in Southeast Asian agricultural landscapes.
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