COLLECTIVE DEFENCE PORTFOLIOS OF ANT HOSTS SHIFT WITH SOCIAL
PARASITE PRESSURE – ELECTRONIC SUPLEMENTARY MATERIAL
Evelien Jongepier, Isabelle Kleeberg, Sylwester Job & Susanne Foitzik
Evolutionary Biology, Johannes Gutenberg University Mainz, Johannes von Müller Weg 6,
55128 Mainz, Germany
Corresponding author:
Evelien Jongepier
Evolutionary Biology
University of Mainz
Johannes von Müller Weg 6
D - 55128 Mainz
Germany
Fax: +49 6131 39 27844
Email: evelien.jongepier@uni-mainz.de
Running title: Defence portfolios and parasite pressure
Table S1. Collection sites and details for 17 Temnothorax host populations of the slavemaker Protomognathus
americanus. Median slavemaker colony sizes refer to the median number of slavemaker workers per colony for
each of the populations. Median slavemaker colony sizes of 0 indicate that the majority of colonies in the
population contained only a slavemaker queen but no slavemaker workers. For some populations long-term
parasite pressure estimates were available which are indicated by the first parasite prevalence and median
slavemaker colony size entry. The second entry refers to the parasite pressure recorded during colony collection.
Slavemaker colony sizes were not recorded for T. longispinosus parasites from Kentucky.
Population
County
Coordinates
Collected
colonies
Experimental
colonies
Parasite
prevalence
Median
slavemaker
colony size
Temnothorax curvispinosus
Illinois
St. Clair
38°13'62''
089°44'97.6"
114
33
- / 0.04
- / 0.0
Indiana
Perry
38°11'88"
086°38'16.3"
94
34
- / 0.03
- / 0.5
Kentucky
Estill
37°48'13"
083°41'83.3"
161
31
- / 0.03
- / 0.0
New Jersey
Burlington
40°00'42"
074°50'10.0"
119
32
- / 0.00
-
Ohio North
Ashtabula
41°50'34"
080°57'55.7"
156
31
0.06 / 0.04
- / 2.0
Ohio South
Delaware
40°14'23"
082°59'10.9"
594
29
- / 0.08
- / 1.0
Virginia
Warren
38°50'05"
078°11'16.0"
96
32
- / 0.05
- / 1.0
West Virginia
Pocahontas
38°06'48"
080°07'88.2"
124
32
- / 0.00
-
Temnothorax longispinosus
Kentucky
Estill
37°48'13"
083°41'83.3"
65
22
- / 0.03
-
Maine
Oxford
42°23'98''
070°51'35.1"
104
33
- / 0.00
-
Massachusetts
Middlesex
42°23'98''
071°11'67.9"
97
33
- / 0.12
- / 1.0
New Hampshire
Sullivan
43°26'41"
072°09'34.6"
105
35
- / 0.00
-
New York
Albany
42°31'95"
074°08'75.3"
963
32
0.12 / 0.19
2.0 / 3.0
Ohio North
Ashtabula
41°50'34"
080°57'55.7"
99
39
0.14 / 0.14
2.0 / 1.0
Quebec
Montreal
45°30'37"
073°36'94.7"
111
32
- / 0.00
-
Vermont
Addison
43°58'25"
073°04'31.6"
102
32
0.07 / 0.16
2.0 / 1.0
West Virginia
Pocahontas
38°06'48"
080°07'88.2"
113
32
0.11 / 0.35
2.0 / 5.0
Table S2. Model selection results from the generalized linear mixed models analysing host collective defences and
slavemaker escape probability in relation to social parasite pressure. Parasite pressure is represented by the
number of slavemaker colonies per host colony (i.e. parasite prevalence) and the median number of slavemaker
workers per colony (i.e. slavemaker colony size). The effect of the two measures of parasite pressure was
evaluated using separate models. Statistics indicated in bold were retained in the final models. All Δd.f. = 1.
Collective immobilization
probability
Predictors
χ2
a
Host evacuation
probability
P
χ2
b
Slavemaker escape
probability c
P
χ2
P
Host colony size
43.952
<0.0001
43.276
<0.0001
28.262
<0.0001
Species
11.805
<0.001
0.053
0.816
21.941
<0.0001
Parasite prevalence
3.957
0.047
7.768
0.005
0.078
0.780
Parasite prevalence x Species
0.071
0.790
0.874
0.350
0.262
0.609
Host colony size
44.192
<0.0001
42.345
<0.0001
28.914
<0.0001
Species
11.661
<0.001
0.095
0.758
18.152
<0.0001
Slavemaker colony size
36.904
<0.0001
28.975
<0.0001
24.263
<0.0001
0.073
0.787
0.014
0.906
0.865
0.353
Slavemaker colony size x Species
Sample size for the models including parasite prevalence (nexperiments/ncolonies/npopulations): a) 599/527/17; b) 606/534/17; c)
442/407/17. Sample size for the models including slavemaker colony size: a) 577/506/16; b) 584/513/16; c) 425/391/16.
Table S3. Model selection results from the generalized linear mixed models
analysing host aggressive defences in relation to social parasite pressure. Parasite
pressure is represented by the number of slavemaker colonies per host colony (i.e.
parasite prevalence) and the median number of slavemaker workers per colony
(i.e. slavemaker colony size). The effect of the two measures of parasite pressure
was evaluated using separate models. Statistics indicated in bold were retained in
the final models. All Δd.f. = 1.
Number of
Number of
immobilizing workers
attacking workers
χ2
P
Host colony size
76.173
<0.0001
1.022
0.312
Species
23.227
<0.0001
30.322
<0.0001
Parasite prevalence
8.340
0.004
0.972
0.324
Parasite prevalence x Species
0.075
0.784
3.563
0.059
Host colony size
75.090
<0.0001
1.067
0.302
Species
23.140
<0.0001
23.329
<0.0001
Slavemaker colony size
56.246
<0.0001
24.328
<0.0001
0.022
0.883
3.160
0.076
Predictors
Slavemaker colony size x Species
χ2
P
Sample size for the models including parasite prevalence (nexperiments/ncolonies/npopulations):
599/527/17. Sample size for the models including slavemaker colony size: 577/506/16.
Defence portfolios and current parasite pressure
Host evacuation probability increased with both the current parasite prevalence (est ± s.e. = 2.850 ±
1.091, z = 2.61, p = 0.009) and the current median slavemaker colony size (est ± s.e. = 0.194 ± 0.075,
z = 2.58, p = 0.010). However, the decrease in collective slavemaker immobilization we observed
when taking available long-term parasite pressure estimates into account, could not be shown for
current parasite pressure. That is, neither the probability of collective immobilization nor the number
of host workers involved in collective immobilization was related to current parasite pressure
(probability: χ2 = 1.03, Δ d.f. = 1, p = 0.311; number of workers: χ2 = 1.80, Δ d.f. = 1, p = 0.180) or
current median slavemaker colony size (probability: z = -1.01, p = 0.310; number of workers: z = 1.40, p = 0.161).
To assess whether any of the populations that were repeatedly sampled exhibited an atypical
response to current parasite pressure, we sequentially removed each of those populations and repeated
the analyses of collective immobilization probability and the number of immobilizing workers. This
showed that the likelihood of collective immobilization decreased with current parasite pressure when
we excluded the T. longispinosus from West Virginia (parasite prevalence: est ± s.e. = -5.209 ± 2.131,
z = -2.44, p = 0.015; median slavemaker colony size: -0.316 ± 0.107, z = -2.94, p = 0.003), but not
when we excluded any of the other host populations (all p > 0.05). Likewise, the number of workers
involved in collective slavemaker immobilization decreased with current parasite pressure when we
excluded the T. longispinosus from West Virginia (parasite prevalence: -4.443 ± 1.374, z = -3.23, p =
0.001; median slavemaker colony size: -0.257 ± 0.072, z = -3.67, p < 0.001), but was unrelated to the
current parasite pressure when including West Virginia but excluding any of the other populations (all
p > 0.05).
These results suggests that, given the current parasite pressure in West Virginia, T.
longispinosus colonies responded differently towards an intruding slavemaker than the remaining host
populations. Comparing long-term and current parasite pressure shows that, in West Virginia, T.
longispinosus hosts have witnessed a substantial increase in both parasite prevalence (long-term: 0.11,
current: 0.35) and median slavemaker colony size (long-term: 2, current: 5). By comparison, parasite
pressure remained relatively constant in the other four populations for which long-term data was
available (Table S1). This may suggest that T. longispinosus defence strategies in West Virginia have
been selected for under different conditions that those experienced at present.