Final answer:
The statement comparing island biogeography to mainland biogeography that is true is option D, which states that mainland species should have higher rates of immigration than island species and the slope of species richness to area should be steeper for mainland species.
Step-by-step explanation:
The statement comparing island biogeography to mainland biogeography that is true is option D, which states that the slope of species richness to area should be steeper for mainland species than for island species and that mainland species should have higher rates of immigration than island species.
Island biogeography refers to the study of life on island chains and how their geography interacts with the diversity of species found there. According to the research by MacArthur and Wilson, islands farther from a mainland have lower migration rates and lower equilibrium species numbers.
Smaller islands are also harder to find and have lower immigration rates, as well as fewer niches for speciation. Additionally, smaller islands support smaller populations, leading to a higher probability of extinction.
On the other hand, mainland biogeography has higher rates of immigration compared to islands due to easier accessibility and more diverse geographical features that promote speciation. The slope of species richness to area is steeper for mainland species because they have a larger area available for species to inhabit. Therefore, option D is correct.