Question 18.86

56. Listed below are the numbers of species of reptiles and amphibians on some Caribbean islands, together with the approximate areas of the islands. (Suggested by Florence Gordon of the New York Institute of Technology, with contributions from Kevin Mitchell and James Ryan of Hobart and William Smith Colleges, Geneva, New York. This table is adapted from Tables 15 and 16 in P. J. Darlington, Zoogeography: The Geographic Distribution of Animals, Wiley, New York, 1957, pp. 483-484.)

Island Area Species
Redonda 1 3
Saba 4.9 5
Montserrat 40 9
Trinidad 2000 80
Puerto Rico 3400 40
Jamaica 4500 39
Hispaniola 30,000 84
Cuba 40,000 76
  1. Plot the number of species versus area on ordinary graph paper and then on log-log graph paper. If you don’t have log-log paper available, use a calculator or spreadsheet to take the logarithms of all the numbers and then graph logarithm of number of species versus logarithm of area on ordinary graph paper. (Note: Trinidad is an outlier from the general pattern; see Chapter 6.)
  2. (b) Is the relationship that you graphed in part (a) proportional? Is it allometric?
  3. What would be the expected number of species on an island of 400 ?
  4. For each 10-fold increase in the island’s size, what happens to the number of species, approximately?