Chengjin Chu and co-authors discuss their latest research which presents a cross-trophic interaction study between the red imported fire ant and plants.
The red imported fire ant (RIFA) is one of the most invasive insects in the world. Many pest management methods have been used to control the spread and damage of RIFA, like quarantine measures and powerful pesticides. However, one may wonder: Do more eco-friendly methods exist? Elton’s ecological resistance (biotic resistance) theory probably helps: The more diverse the local community, the greater resistance it can provide.
We expanded this theory across trophic levels to explore how tree diversity, a dominant driver of community complexity, influences the RIFA invasion. We sampled data through a field survey in a subtropical plantation forest in Southeast China, finding that the plots with more tree species had lower RIFA abundance.
Tree diversity seemed to work, but how? We found that the tree species, Ilex rotunda, seemed to attract RIFA. That is because I. rotunda is attractive to aphids who can provide honeydew to RIFA to exchange for care and protection. The abundance of I. rotunda is lower in higher tree diversity areas and could be the cause of how tree diversity works.
Unexpectedly, we found more RIFA mounds in the plots with higher tree diversity. One may ask: why did tree diversity pose contrasting effects on the RIFA abundance and mound numbers? In fact, once the queen begins to breed workers, food resource (e.g. arthropod preys) will be the key factor for the mound development.
Our study showed that forests with higher tree diversity could recruit more ample food resources that, in turn, increased the number of RIFA mounds, though nearly 99% of the mounds were without living RIFA. Notably, other carnivorous ants also contributed to the resistance of RIFA, but our study did not find any significant relationships between tree diversity and other ants.
Given that previous studies reported the positive effects of tree diversity on ants, we suggested that other ants could be one of the key pathways for how tree diversity strengthens the ecological resistance to RIFA invasion. Our study revealed the complex relationships between tree diversity and RIFA and stressed that diversifying forest tree species could mitigate RIFA invasion via limiting the population size.
Read the full article “Tree species richness suppresses red imported fire ant invasion in a subtropical plantation forest” in Journal of Applied Ecology.
