Refer to the following information to answer the questions below.
Fossils of Lystrosaurus,a dicynodont therapsid,are most common in parts of modern-day South America,South Africa,Madagascar,India,South Australia,and Antarctica.It apparently lived in arid regions,and was mostly herbivorous.It originated during the mid-Permian period,survived the Permian extinction,and dwindled by the late Triassic,though there is evidence of a relict population in Australia during the Cretaceous period.The dicynodonts had two large tusks,extending down from their upper jaws.The tusks were not used for food gathering,and in some species were limited to males.Food was gathered using an otherwise toothless beak.Judging from the fossil record in sedimentary rocks,these pig-sized organisms were the most common mammal-like reptiles of the Permian period.
-A hypothetical island lies far from any other landmasses.There are many different types of plants,but only one animal,a beetle,that can fly or walk from plant to plant and feeds by chewing leaves.Given that the beetle is not exploiting all of the resources on the island,which morphological change would be most likely to trigger an adaptive radiation of the beetles?