There is a correlation between algae height and the snout-to-vent length of a group of marine iguanas in the galapagos; as algae height increases for a given island, so does iguana length. why would the body size of this population of iguanas correlate with algae height?
differential reproduction of larger animals is favored when adequate nutrition is supplied by larger algae.
increased variation in animal size is favored when large plant species are present in a healthy ecosystem.
overproduction of smaller animals is favored when algae swards are short and vice versa when algae swards are long.
traits are exchanged between iguana and algae populations so that taller algae result in larger iguana populations