Final answer:
Compared to plants with ant colonies, those without weighed less and were attacked by insect herbivores more often, demonstrating the protective benefits of the mutualistic ant-acacia system.Option 3 is the correct answer.
Step-by-step explanation:
Janzen's studies of the ant-acacia system found that compared to plants with ant colonies, those without an associated ant colony weighed less; more often and were attacked by insect herbivores more often. This mutualistic relationship between the ants and acacia plants benefits the plants by having the ants defend against herbivores and pathogens, while the ants benefit from shelter and food provided by the acacia. Without the ant colonies, the acacia plants are less defended, leading to increased attacks from herbivores and a potential reduction in plant biomass.
In Janzen's exploration of the ant-acacia system, the absence of ant colonies had profound implications for acacia plants. Those lacking ant associations exhibited reduced weight, increased vulnerability to insect herbivores, and a higher frequency of attacks. This highlights the mutualistic nature of the relationship: ants defend acacia plants against herbivores and pathogens, while the plants offer shelter and sustenance to the ants. Without ant protection, acacias face heightened herbivore pressure, potentially compromising their biomass. Janzen's findings underscore the intricate interdependence in this ecological partnership, emphasizing the pivotal role ants play in enhancing the defensive capabilities and overall resilience of acacia plants in their natural environment.