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Online supplement for: An empirical test of stable species coexistence in an amphipod
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species complex
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Rickey D. Cothran1, 2, Patrick Noyes1, and Rick A. Relyea3
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Department of Biological Sciences and Pymatuning Laboratory of Ecology, University of
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Pittsburgh, 4249 Fifth Ave., Pittsburgh, PA 15260, USA
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1
Authors contributed equally to the manuscript
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2
Current address: Department of Biological Sciences, Southwestern Oklahoma State University,
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100 Campus Drive, Weatherford, OK 73096, USA
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Current address: Department of Biological Sciences, Rensselaer Polytechnic Institute, 110 8th
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Street, Troy, NY 12180, USA
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Corresponding Author: RDC (rickey.cothran@swosu.edu)
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Abiotic response variables
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We used a multivariate analysis of variance (MANOVA) to assess whether low and high nutrient
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mesocosms differed in dissolved oxygen (DO), pH, and temperature. Higher DO and pH
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typically indicate more primary productivity. We found a multivariate effect of nutrient in the
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near-shore experiment (F3, 26 = 3.357, P = 0.034) but not in the off-shore experiment (F3, 26 =
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2.006, P = 0.138).
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In the near-shore experiment, univariate analyses revealed that pH differed between
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nutrient treatments (F3, 26 = 3.357, P = 0.034), but DO (F3, 26 = 3.357, P = 0.034) or temperature
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(F3, 26 = 3.357, P = 0.034) did not. The pH was higher in high-nutrient mesocosms than low-
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nutrient mesocosms (Table S1).
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Although the MANOVA showed no significant nutrient effect on abiotic response
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variables, the off-shore experiment showed a clear pattern that was consistent with the results
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found in the near-shore experiment (Table S1). Univariate tests further confirmed this result;
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high-nutrient mesocosms had higher pH than low-nutrient mesocosms (F3, 26 = 3.357, P = 0.034),
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but DO (F3, 26 = 3.357, P = 0.034) and temperature (F3, 26 = 3.357, P = 0.034) did not differ.
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Table S1. Abiotic response variables (dissolved oxygen, pH and temperature) taken during the
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experiment. Higher values for dissolved oxygen and pH typically indicate a more productive
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environment. Values are means (± 1 SD).
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Experiment
pH
Dissolved
oxygen
Temperature
Low nutrients
9.66
(0.27)
13.96
(3.77)
29.65
(0.75)
High nutrients
9.91
(0.24)
15.23
(4.44)
29.31
(0.73)
Low nutrients
9.56
(0.36)
19.19
(3.78)
30.11
(0.41)
High nutrients
9.82
(0.2)
20.31
(3.37)
30.29
(0.27)
Near-shore experiment
Off-shore experiment
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Supplemental Figure Legends
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Fig. S1 Female abundance for each resident species before the invasion. Panels on the left are for
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mesocosms assigned to species A, the middle two panels are for mesocosms assigned to invader
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species B, and the right two panels are for mesocosms assigned to invader species C. The bold
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line indicates the median abundance, the bottom of the box is the 25th percentile and the top of
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the box is the 75th percentile. T-bars extend 1.5 times the height of the box. Outliers (values
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outside of the T-bars) are signified by open circles and extreme outliers (> 3 times the height of
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the box) by *
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Fig. S2 Adult abundance for each species in the October 2011 sample (63 to 64 days after
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invasion). The left panels are for invader species A, the middle panels are for invader species B,
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and the right panels are for invader species C. See Figure S1 for an explanation of data
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distributions
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Fig. S3 Female abundance for each species in the May 2012 sample (262 to 263 days after
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invasion). The left panels are for invader species A, the middle panels are for invader species B,
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and the right panels are for invader species C. See Figure S1 for an explanation of data
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distributions
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Fig. S4 The relative abundance of the invader species in the off-shore experiment in the May
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2012 sample as a function of the absolute abundance of each resident and the total abundance of
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both residents. Panels for invader species A (a-c), invader species B (d-f) and invader species C
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(g-i) are presented
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Fig. S5 The relative abundance of the invader species in the near-shore experiment in the May
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2012 sample as a function of the absolute abundance of each resident and the total abundance of
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both residents. Panels for invader species A (a-c), invader species B (d-f) and invader species C
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(g-i) are presented
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