Read the article "Local and latitudinal variation in abundance: the mechanisms shaping the distribution of an ecosystem engineer" by Gregory M. Crutsinger1, Ange รยlica L. Gonzalez1, Kerri M. Crawford2 and Nathan J. Sanders3
Website https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3709108/
1.What is the hypothesis of the paper?
2.Is this a correlative or causative study? Explain