Ecologists often measure the biodiversity of a region by the number of distinct species that exist in the region. Nature reserves are lands specifically designated by the government to help maintain biodiversity. Care must be taken when setting up a network of nature reserves so that the maximum number of species can exist in the network. Geography matters as well, as putting reserves too close together might subject the entire network to risks, such as devastation from wildfires. The initial step in this type of planning usually involves mapping the number of species that exist in each region. The file species contains an estimate of the number of unique species that exist in each of the 50 states in the United States.

a. Create a choropleth map that displays number of species by state. Add data labels to the choropleth map to show the number of species in each state.

b. Comment on the distribution of species over the United States. Which regions of the United States have relatively many species? Which regions have relatively few species?

c. Which two states have the most species? Why might this be expected?

d. The choropleth map in part (a) helps to identify which states have the most species.
However, how could one construct a choropleth map that identifies the states with the highest density of species?