Appendix C. A table of exploratory analysis of numerous growth metrics of Venerupis and Protothaca.
Growth Metric (units)
Change in Venerupis value
Change in Protothaca value
Venerupis advantage
F
P
Wet tissue mass (g)
2.93
2.30
+0.63
14.6
0.00018
Height (mm)
3.1
0.60
+2.51
199.9
<0.000001
Length (mm)
3.57
0.43
+3.14
225.3
<0.000001
Thickness (mm)
2.28
0.38
+1.89
297.7
<0.000001
Gonad dry mass (g)
0.20
0.074
+0.13
17.6
0.000043
Dry tissue (g)
0.51
0.17
+0.34
52.2
<0.000001
Relative dry tissue growth
[(final – initial weight)/initial]0.63
0.22
+0.41
52.5
<0.000001
Dry tissue and shell (g)
3.01
0.42
+2.58
218.3
<0.000001
Notes: This table of exploratory analysis indicates that there are large, consistent differences in Venerupis and Protothaca that are not obscured by differential effects of other factors on the two species (e.g., site effects, experimental manipulations). The table presents the average change in different growth metrics of clams over the course of the experiment (i.e., final – initial values) for each enclosure employed in the field experiment averaged across all treatments. I obtained initial values for tissue measurements through correlations of external measurements to tissue mass of clams dissected at the beginning of the experiment taken from a random subset of the cohort of clams used in the experiment. F and P values are listed for one-way ANOVAs analyzing the effect of species (fixed factor) on the average response within each enclosure. To control for the number of multiple comparisons being done, Bonferroni correction for this family of tests set the significance level at 0.0063 (0.05/8). N for all analyses was Venerupis = 69, Protothaca = 108. Protothaca has a higher N because Venerupis was absent by design in one-third of clam enclosures (minus an additional three enclosures where all Venerupis individuals were lost). Incorporating the extra third of Protothaca enclosures where Venerupis was absent should bias Protothaca’s values upward (if at all) since Protothaca would experience no immediate interspecific competition within these enclosures.