PATTERN AND PROCESS IN COMPETITION
37
the numbers of adults or pupae produced by the two species, although
D. melanogaster had a higher production than D. simulans when the
initial larval density was increased above this value. During interspecies
competition between equal numbers of the two species at combined
densities of 10, 20, 40, 80 and 120 larvae there was also no significant
difference in the numbers of adults of each species produced. If we
allow K , and K , to stand for the maximum production of adults of
D. melanogaster and D . simuluns respectively at each experimental
density up to saturation in single-species cultures, and consider N , and
N , to be the number of adults of each from mixed populations, we can
make the comparison shown in Table I1 and can test for the values of
the interactions between them at each of the five density levels.
TABLE I1
Numbers of Adult D. melanogaster (K, and N,) and D. simulans (K,
and N,) in Single-Species and Two-Species Cultures (From Miller, 19643)
Initial
Single-species
2-species
Larval
Density
K ,
Ka
Nl
N ,
10
7 -8
7.9
4.3
4.1
20
17-0
16.9
8 -7
7 *7
40
33.6
33.6
15.8
14.3
80
58.8
54.4
28.2
28.2
120
74.6
69.0
32.3
37-2
Analysis of variance for the values of K,, K,, N , and N , at the five
levels of density permitted the following conclusions:
(1) K , N K,: the conditions of the experimental environment had
the same survival value for both species at the density levels tested.
(2) N , NN,: the total resources of the environment were shared
equally between the two species.
(3) ( K , - N,) N N , : the effect of N , on N , was the same as the
effect of N , on members of its own species and therefore a = 1.
(4) ( K , - N , ) N N,: the effect of N , on N , was the same as the
effect of N , on members of its own species and therefore / 3 = 1.
(6) a N /3: the effect of N , on N , was the same as the effect of N ,
on N,.
To test for differences in the values of a and / 3 the logarithms of
( K , - N,), ( K , - N , ) and the observed values for N , and N , were
andysed for variance. The comparison log a - log /3 given by:
Clog ( K , - N , ) - 1% N 2 1 - [log (K2 - N,) - 1% N 1 1 (6)
37
the numbers of adults or pupae produced by the two species, although
D. melanogaster had a higher production than D. simulans when the
initial larval density was increased above this value. During interspecies
competition between equal numbers of the two species at combined
densities of 10, 20, 40, 80 and 120 larvae there was also no significant
difference in the numbers of adults of each species produced. If we
allow K , and K , to stand for the maximum production of adults of
D. melanogaster and D . simuluns respectively at each experimental
density up to saturation in single-species cultures, and consider N , and
N , to be the number of adults of each from mixed populations, we can
make the comparison shown in Table I1 and can test for the values of
the interactions between them at each of the five density levels.
TABLE I1
Numbers of Adult D. melanogaster (K, and N,) and D. simulans (K,
and N,) in Single-Species and Two-Species Cultures (From Miller, 19643)
Initial
Single-species
2-species
Larval
Density
K ,
Ka
Nl
N ,
10
7 -8
7.9
4.3
4.1
20
17-0
16.9
8 -7
7 *7
40
33.6
33.6
15.8
14.3
80
58.8
54.4
28.2
28.2
120
74.6
69.0
32.3
37-2
Analysis of variance for the values of K,, K,, N , and N , at the five
levels of density permitted the following conclusions:
(1) K , N K,: the conditions of the experimental environment had
the same survival value for both species at the density levels tested.
(2) N , NN,: the total resources of the environment were shared
equally between the two species.
(3) ( K , - N,) N N , : the effect of N , on N , was the same as the
effect of N , on members of its own species and therefore a = 1.
(4) ( K , - N , ) N N,: the effect of N , on N , was the same as the
effect of N , on members of its own species and therefore / 3 = 1.
(6) a N /3: the effect of N , on N , was the same as the effect of N ,
on N,.
To test for differences in the values of a and / 3 the logarithms of
( K , - N,), ( K , - N , ) and the observed values for N , and N , were
andysed for variance. The comparison log a - log /3 given by:
Clog ( K , - N , ) - 1% N 2 1 - [log (K2 - N,) - 1% N 1 1 (6)