Two species of leaf eating beetles (species A and species B) have existed on an island in the Pacific Ocean for over 100,000 years. In
1964, a third species of leaf-eating beetle (species C) was
accidentally introduced on the island. The population size of each
species has been regularly monitored as shown in the graph below.
Population Density
(beetles/m)
VARIATION IN POPULATION DENSITY OF BEETLES
40
35
30
25
Species A
20+
Species B
... Species C
15
10+
5
0
1964 1974 1984 1994 2004
Year
What is the best explanation for the stability of population A and the decline of population B