Supplementary Information for:
‘Ecosystem consequences of species richness and composition in pond food webs’
Downing, A.L. & Leibold, M.A.
Additional materials include two tables. The first table details the compositional
treatments of the experiments and the final biomasses of manipulated species. The second
table contains data suggesting that different initial stocking levels of invertebrate grazers
do not strongly affect ecosystem attributes.
TABLE 1: Description of compositional treatment and diversity in biodiversity
experiment. Species A-G are macrophytes, species H-N are grazers, and species O-U are
predators (legend at bottom of Table). Compositions 1-7 had 1 species per functional
group, compositions 8-14 had 3 species per functional group and compositions 15-21 had
5 species per functional group. Table entries are mean final biomass estimates (mg/tank)
for each treatment (upper value) and the standard deviation (lower value), for grazers and
predators the mean final number of individuals per tank is shown in parentheses. Entries
of ‘0’ indicate treatments in which species were initially stocked as part of the
experimental design but went extinct during the course of the experiment. Italicized
entries indicate species that were not originally stocked in a treatment as part of the
experimental design, but had invaded by the final census.
TABLE 1. Species treatment combinations and final biomasses.
Spp.δ
1
A -
2
-
B
0
C
3
-
Composition
4
-
5
-
6
-
7
-
-
-
-
-
-
0
-
-
-
-
-
-
D
-
-
-
-
-
E
-
-
1.571
1.597
-
2.268
0.534
-
-
-
-
-
F
-
-
-
-
-
-
0.501
0.178
-
-
G
0.747
0.311
-
H
-
-
-
-
-
I
-
-
-
-
-
J
K
L
0.349(13) 0.378
0.282(3)
0.395
1.076(73) 0.350
-
-
12.470
2.894
0.551(21)
0.477
-
-
0.008(.3) 0.464(19) 0.107(5)
0.017
0.928
0.214
-
0.133(11)
0.267
-
-
3.67(19)
1.586
0.001(1)
0.002
0.074(19)
0.057
-
M -
-
-
N
-
-
-
O
0.020(5.3)
0.006
0.015(1)
0.018
-
0.004(1)
0.005
-
Q
0.018(4.8)
0.006
0.019(1.3)
0.019
-
5.087(32) 5.443
0.084(39) 0.036
0.552(143) 0.018(4.8) 0.332
0.022
-
-
-
R
-
-
-
-
S
-
-
-
-
0.046(1.5) 0.040
0.079(1.8) 0.043
-
T
-
-
-
-
-
-
-
U
-
-
0.142(3.5)
0.078
-
-
-
-
P
-
Table 1 cont’d.
Spp.
8
9
A 0.002
0.003
B C
1.092
0.528
1.305
1.122
-
1.146
0.245
1.251
1.119
-
G
0.312
0.325
-
H
-
-
I
0
0
D
E
F
-
11
-
0
-
0
0
-
-
-
-
-
0.479
0.470
0
1.308
0.256
-
-
0
-
0.584
0.351
0
-
-
-
-
4.697
1.052
-
-
0
0.436
0.457
0.016(6.5)
0.005
-
J
0.069(1)
0.095
K 1.687(95) 0.738(57) 1.350(92)
0.360
0.545
1.054
L 0.049(103) 0.028
M 4.384(31)
1.777
N O
P
0.012(3)
0.009
-
0.040(10.5) 0.003(1)
0.025
0.004
0
Q
-
0
-
R
-
-
-
S
-
-
0
T
0.035(1.8) 0.090(4.5) 0.060(3)
0.034
0.058
0.043
0.112(2.8) 0.039
U
Composition
12
13
0
10
-
-
3.546
0.518
0.019(7.5) 0.018(7)
0.008
0.006
-
0.255(5)
0.235
0.450(25) 0.677(41)
0.278
0.250
0.036(76) 0.043
3.479(20) 1.951
0.110(50) 0.219
0.094(25) 0.031(8)
0.046
0.020
0.004(0.3) 0
0.008
-
14
0.009
0.017
-
0.028(11)
0.008
-
-
0.301(6)
0.295
1.385(68) 0.035(2)
1.068
0.074
0.038(80) 0.008
-
0.037(17)
0.016
0.058(15) 0.103(27)
0.061
0.043
-
0.078(0.3)
0.015
0.034(0.8) 0.068
0.016(0.3) 0.016(0.3)
0.032
0.032
0.055(2.8) 0.041
0.102(2.5) 0.193(4.8)
0.023
0.077
Table 1 cont’d.
Spp.
15
16
A 0
0.006
0.012
B C
D
E
F
G
17
0.050
0.035
-
18
0.038
0.027
-
0.703
0.314
0.687
0.871
-
0.874
0.625
0.371
0.391
0
0.591
0.336
0.517
0.565
0
0.508
0.284
0.538
0.642
0
0.209
0.199
3.591
1.092
-
0.205
0.225
-
-
-
2.811
0.376
H
0.014(5.8) 0.011(4.3)
0.008
0.006
I 0
0
0.010(0.3)
0.021
J 0.022(0.3) 0.044
K 0.238(23) 0.005(0.3) 1.377(81)
0.167
0.010
1.036
L 0.041(86) 0.022
M 2.845,10 5.670(34) 2.888(20)
1.494
1.583
0.759
N 0.008(4) 0.058(26) 0.002(0.8)
0.011
0.064
0.001
O 0.007(2) 0.012(3) 0.012(3)
.007
0.008
0.007
P 0
0.004(0.3) 0
0.008
Q 0
0.031(1)
0.036
R 0.045(1) 0.079(2) 0.068(2)
0.052
0.043
0.026
S 0.032(0.5) 0.096(2)
0.037
0.037
T 0.020(1) 0.025(1) 0.035(2)
0.016
0.05
0.019
U 0.051(1)
0.023
Composition
19
20
0.013
0.019
0
0
-
-
0.423
0.485
-
0.379
0.256
0
0.134
0.169
3.089
2.246
0.716
0.611
0.019(7.5) 0.016(6.3)
0.003
0.003
0
0
0.187
0.072
1.251
0.488
0.016(6.5)
0.003
0.101(1.5)
0.201
0
0.230(4.8) 0.299(3.5)
0.278
0.347
0.159(14) 0.136(7)
0.114
0.271
0.054(115)
0.034
3.104(9) 3.241(14) 1.718
1.061
0.003(1.3) 0
0.043(20)
0.005
0.067
0.054(14) 0.028(7) 0.014
0.010
0
0.004(0.3)
0.008
0
0.068(2)
0.045
0.096(2)
0.037
0.061(2)
0.023
0.096(2)
0.037
0.025(1)
0.010
0.071(2)
0.051
0.045(1)
0.064
0.064(1)
0.052
0.025(1)
0.019
0.041(1)
0.033
21
0
0.612
0.090
0.378
0.270
0.212
0.163
1.395
0.338
0
0.75(82)
0.834
0.028(59)
0.010
2.99(9)
0.676
0.034(16)
0.025
0.10(25)
0.066
0
0.02(0.5)
0.018
0.112(2)
0.032
0.041(1)
0.033
Table 1 footnote: δ Species key. Macrophytes: A = Potamageton compréssus, B =
Utricularia vulgaris, C = Myriophyllum verticullatum, D = Elodea occidentale, E =
Valisneria americana, F = Ceratophyllum demersum, G = Potamageton crispus;
periphyton grazers: H = Crangonyx richmondensis, I = Rana catesbeiana, J = Rana
clamitans, K = Physa gyrina, L = Hyallela azteca, M = Helisoma trivolis, N =
Trichocorixa sp; and invertebrate predators: O = Neoplea striola, P = Ambrysus sp, Q
= Gyrinus sp, R = Acilius sp, S = Belostoma flumireum, T = Notonecta undulata, U =
Notonecta sp.
Table 2. ANOVA results for an experiment§ testing for biomass and ecosystem
effects in response to different starting densities of 5 periphyton grazers.
community biomass
periphyton grazer (mg)
phytoplankton (µg chla/l)
periphyton (µg chla/m2)
Hyallela azteca
F
p
16.4 <0.001
2.61
0.182
2.66
0.178
ecosystem rates
decomposition (g C/day) 2.97
productivity (mg 02/hour) 0.67
respiration (mg 02/hour) 0.00
community biomass
periphyton grazer (mg)
phytoplankton (µg chla/l)
periphyton (µg chla/m2)
0.16
0.46
1.00
Rana catesbeiana
F
p
1.04
0.37
0.85
0.41
0.71
0.45
ecosystem rates
decomposition (mg C/day) 0.44
productivity (mg 02/hour) 0.95
respiration (mg 02/hour) 0.00
0.54
0.38
1.00
Helisoma trivolis
F
p
1.43
0.30
0.15
0.72
7.41
0.053
Physa gyrinus
F
p
2.57
0.18
2.37
0.20
0.95
0.23
6.24
0.53
0.01
2.57
0.10
0.80
0.07
0.51
0.93
0.18
0.77
0.42
Crangonyx richmondensis
F
p
2.43
0.19
2.46
0.19
2.47
0.19
0.35
0.08
0.67
0.58
0.79
0.46
Table 2 Footnote: § Treatments consisted of low (10 individuals) or high (50
individuals) starting densities of periphyton grazer in a background of identical food
webs (zooplankton, phytoplankton, periphyton, macrophytes, and microbes). Response
variables were measured 8 weeks after the treatments were established to test for effects
of starting density on community and ecosystem attributes using methods that were
almost identical to those described in Downing and Leibold, ms. With the exception of
Hyallela azteca which revealed significantly higher grazer biomass at high starting
density, there were no significant effects of starting density on final grazer biomass.
More importantly, there were no significant effects on any of these ecosystem attributes
(even in the case of Hyallela azteca).