1
1
Zhishu Xiao, Zhibin Zhang, Charles J. Krebs. Long-term seed survival and dispersal
2
dynamics in a rodent-dispersed tree: Testing the predator satiation hypothesis and the
3
predator dispersal hypothesis.
4
5
Supporting information
6
Additional Supporting information may be found in the online version of this article.
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Appendix S1. Detailed methodology for annual census of both rodent and seed abundance.
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Table S1. Statistical results comparing seed crop size per plant between all of the pairs of the
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8 years of samples.
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Table S2 Statistical results from linear mixed models for each dispersal parameter.
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Fig. S1 Survivorship curves for seeds remaining at the source after placement.
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Fig. S2 Annual changes of the mean time (weeks) to seed removal at source or seed recovery
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at primary caches.
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Fig. S3 Relationships between annual crop size or relative seed availability and the mean
15
time to seed removal at source or the mean time to recovery for primary caches.
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2
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Appendix S1 Detailed methodology for annual census of both rodent and seed abundance.
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Annual changes in rodent abundance: Surveys were conducted in the same stand used to
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quantify oil tea seed crops from 2002 to 2009 during autumn (i.e. the dispersal season of oil
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tea). To estimate the density of rodent seed predators and dispersers, we used large wired
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cage traps (30×25×20 cm, of our own design approved by the Institute of Zoology, Chinese
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Academy of Science) baited with peanuts or chestnuts, and small pieces of cabbage as food
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and water. Dry leaves of local species were provided as nest materials. We set 20 traps
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(2002-2003) and 40 traps (2004-2009) along two or three trap lines for three consecutive
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nights during September or October each year. Each trap and each trap line were set 10-15
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m apart. Traps were placed at 1800-1900 hours in the evening and checked 12 hours later.
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All captured animals were identified to species, recording sex and reproductive status
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(females pregnant, lactating or not; males with testes descended or not). Individuals were
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marked with a colored paint to allow identification during the three-day survey if they were
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recaptured. We then released each animal at their original point of capture. In this study, we
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captured eight rodent species from 2002 to 2009: Leopoldamys edwardsi (average weight:
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281.2 ± 12.8 (SE) g, n = 65), Niviventer fulvescens (65.2 ± 6.2 g, n = 48), N. confucianus
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(62.2 ± 2.8 g, n = 77), Apodemus chevrieri (46.3 ± 2.8 g, n = 26), A. draco (26.2 ± 2.5 g, n
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= 9), A. latronum (32.4 ± 4.3 g, n = 13), Rattus nitidus (122.1 ± 6.7 g, n = 54) and R.
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norvegicus (99.3 ± 13.4 g, n = 8). We considered two parameters to measure the relative
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abundance each year: trap success for all rodent species, and minimum number alive
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(MNA) per 100 trapnights for both seed dispersers and seed predators (see similar analysis
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in Hoshizaki & Hulme 2002).
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Annual changes in seed abundance: In 2002 we randomly selected 60 similar-size
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fruiting oil tea individuals with reproductive organs (i.e. fruits or flowers or both) in the
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Camellia-rich stand. During 2002-2009 we collected all the fruits from the 60 marked
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plants each autumn (September 20-26) before the fruits and their seeds fell to the ground.
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We then dissected each fruit and counted the number of seeds for each individual fruit, and
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totaled the number of seeds for each plant. Seeds damaged by insect seed predators (e.g.
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Dichocrocis punctiferalis) were also recorded but not analyzed in this paper.
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The Wilcoxon signed-rank test was used to test the difference of average production
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of seeds per tree between any two of the 8-year samples. Seed crop data were transformed
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by log10 (seeds+1). We found that seed crop in either 2007 or 2008 was significantly higher
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than that in any of the other six years (Table S1). Thus, we treated the years 2007 and 2008
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as mast years and the remaining years as non-mast years, but seed crop in 2006 was
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intermediate between between mast years and the other non-mast years (Table S1).
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References
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Hoshizaki, K. & Hulme, P.E. (2002) Mast seeding and predator-mediated indirect
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interactions in a forest community: evidence from post-dispersal fate of
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rodent-generated caches. Seed dispersal and frugivory: ecology, evolution and
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conservation (eds D.J. Levey, W.R. Silva & M. Galetti), pp. 227-239. CABI Publishing,
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Wallingford, Oxfordshire.
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4
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Table S1 Statistical results comparing seed crop size per plant between all of the pairs of
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the 8 years of samples. The data shown in the table are the difference in mean size between
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each pair of the 8 years and the probability of this difference in parenthesis. NS, no
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significance.
Year
2003
2004
2005
2006
2007
2008
2009
28.4
26.3
23.6
-17.3
-124.6
-58.7
17.2
(NS)
(NS)
(NS)
(0.034)
(< 0.001)
(< 0.001)
(NS)
-2.1
-4.8
-45.8
-153.0
-87.1
-11.3
(NS)
(NS)
(< 0.001)
(< 0.001)
(< 0.001)
(NS)
-2.7
-43.6
-150.9
-85.0
-9.2
(NS)
(< 0.001)
(< 0.001)
(< 0.001)
(NS)
-41.0
-148.2
-82.3
-6.5
(0.019)
(< 0.001)
(< 0.001)
(NS)
-107.3
-41.4
34.5
(< 0.001)
(0.001)
( 0.001)
65.9
141.8
(NS)
(< 0.001)
2002
2003
2004
2005
2006
2007
75.8
2008
(< 0.001)
65
66
5
67
Table S2 Statistical results from linear mixed models for each dispersal parameter: one model
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with average crop size (ACS) and annual metabolic rodent abundance (AMRA) and year as a
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random factor, and the other model with per capital seed availability (PCSA) as a fixed factor
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and year as a random factor. Fixed factors in bold indicate significant differences (P < 0.05).
Fixed factors
Estimate±SD
df
t
p
Intercept
0.174±0.339
5
0.512
0.630
ACS
0.666±0.139
5
4.771
0.005
-0.324±0.134
5
-2.409
0.061
Intercept
0.852±0.084
6
10.149
0.0001
PCSA
0.483±0.134
6
3.606
0.011
4.620±1.346
4
3.433
0.023
ACS
-1.997±0.758
4
-2.635
0.056
AMRA
-1.634±0.565
4
-2.892
0.045
ACS*AMRA
0.927±0.315
4
2.939
0.042
Intercept
1.164±0.063
6
18.406
< 0.001
PCSA
0.096±0.101
6
0.950
0.379
The time to removal
AMRA
The time to recovery
Intercept
71
72
73
6
74
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Fig. S1 Survivorship curves for seeds remaining at the source after placement during the first
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seven weeks (2002-2009).
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2002
2006
2003
2007
2004
2008
2005
2009
Proportion of seeds remaining
1.0
0.8
0.6
0.4
0.2
0.0
0
78
79
1
2
3
Weeks after placement
5
7
7
80
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Fig. S2 Annual changes of the mean time (weeks) to seed removal at source or seed recovery
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at primary caches.
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Mean time (weeks)
30
25
20
Time to removal at source
Time to recovery at caches
15
10
5
0
2002 2003 2004 2005 2006 2007 2008 2009
84
85
86
8
87
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Fig. S3 Relationships between annual crop size (average crop size per plant, log-10 scale,
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Panels A and C) or relative seed availability (annual crop size divided by the sum of
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metabolic scaling body mass from each rodent species each year, log-transformed, Panels B
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and D) and the mean time (weeks, log-10 scale) to seed removal at source (Panels A and B)
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or the mean time (weeks, log-transformed) to recovery for primary caches (Panels C and D).
0.8
1.2
1.2
1.4
1.6
1.8
2.0
2.2
2.4
1.4
0.0
0.4
harvest
0.8
0.4
1.4
0.0
harvest
1.2
93
-1.2
-0.8
0.2
1.2
0.8
1.4
1.6
1.8
Masting
95
0.0
1.0
recovery
1.2
1.0
0.8
recovery
1.2
94
-0.4
RSA
Masting
2.0
2.2
2.4
-1.2
-0.8
-0.4
RSA
0.0 0.2