Final answer:
Based on ecological principles and the evidence provided, Boreblasters likely dispersed due to a bottom-up effect caused by an increase in umbrella trees, which aligns with how changes at the plant level can impact animal populations. The correct answer is option c.
Step-by-step explanation:
When considering the effects on Boreblasters' dispersion and whether this is likely due to a top-down or bottom-up effect triggered by changes in either spotted gliders or umbrella trees, it's important to define these ecological terms. A top-down effect typically refers to a change at the predator level affecting the prey and further down the food chain. On the other hand, a bottom-up effect involves changes at the primary producer level, such as plants, that then affect the higher trophic levels.
Based on phytodemographic studies and the evidence provided about seedling recruitment in overhunted forests leading to changes in plant species abundance, it suggests that changes in animal populations can have significant repercussions on plant communities. In the case of the Boreblasters, if an increase in umbrella trees leads to a greater spread of Boreblasters because they offer more resources or habitat, this would be a bottom-up effect. Conversely, if a change in the number of spotted gliders, which may prey on or compete with Boreblasters, leads to changes in Boreblaster distribution, this would point to a top-down effect.
The correct option that is best supported by the evidence would likely be a bottom-up effect caused by an increase in umbrella trees, as the data suggest that changes at the plant level can significantly impact animal dispersion.