Lectures on species interactions and competition

Zero Net Growth Isocline diagrams (ZNGIs)
(Tilman 1982)
ZNGI diagrams devised by Tilman can help visualize outcomes of
pairwise competitive interactions.
(a) Isocline for species 1:
• The line is the isocline for species 1 and represents various combinations of
species 1 and 2 that result in the joint carrying capacity, K 1 .
• N 1 + N 2 = K 1 , so when N 1 = 0, N 2 = K 1 / , and when N 2 = 0, N 1 = K 1 .
• To reach equilibrium, Species 1 will increase left of the line and decrease right
of the line.