Ecological Archives E081-013-A1

James E. Byers. 2000. Competition between two estuarine snails: implications for invasions of exotic species. Ecology 81:1225-1239.


Average relative changes [(final - initial)/initial] of different per capita metrics of growth (means, with 1 SD in parentheses) of both sizes and species of snail for all years. C = Cerithidea californica; B = Batillaria attramentaria.

Density is the number of snails in each enclosure pen (0.1 m2). Length was measured from apex to anterior tip of aperture, and width was measured at largest whorl at mouth. Wet mass represents the entire body mass (shell + tissue) of the snail. Pairwise t tests were performed to compare the two species at each density level for each of the three metrics.
*P < 0.05; **P < 0.01 (significant differences).

Year

Size class

Species

Density

Length (mm)

Width (mm)

Wet mass (g)
N
1995

Small

C

12
      0.33 (0.048) 0.27 (0.042) 1.28 (0.21) 4
   

B

12
      0.31 (0.038) 0.30 (0.021) 0.99 (0.13) 4
   

C

23
      0.31 (0.052) 0.26 (0.05) 1.03 (0.035) 3
   

B

23
      0.28 (0.33) 0.23 (0.034) 0.87 (0.10) 3
   

C

35
      0.25 (0.024) 0.21 (0.015) 0.84 (0.068) 3
   

B

35
      0.28 (0.048) 0.22 (0.011) 0.93 (0.014) 2
   

C

46
      0.26 (0.0062) 0.19 (0.039) 1.16 (0.23) 2
   

B

46
      0.28 (0.024) 0.28 (0.0111) 0.95 (0.049) 2
   

C

69
      0.26 (0.037) 0.21 (0.034) 0.95 (0.15) 3
   

B

69
      0.29 (N/A) 0.26 (N/A) 0.93 (N/A) 1
   

C

92
      0.21 (0.021) 0.19 (0.031) 0.79 (0.04) 2
   

B

92
      0.27 (0.027) 0.27 (0.032) 0.89 (0.11) 3
 

Large

C

12
      0.050 (0.019) 0.080 (0.025) 0.21 (0.054) 4
   

B

12
      0.13 (0.025)** 0.11 (0.023) 0.29 (0.046) 4
   

C

23
      0.040 (0.026) 0.083 (0.056) 0.11 (0.068) 3
   

B

23
      0.12 (0.035)* 0.12 (0.031) 0.30 (0.019)** 3
   

C

35
      0.015 (0.0059) 0.047 (0.017) 0.064 (0.0063) 2
   

B

35
      0.12 (0.0087)** 0.11 (0.13)** 0.25 (0.28)** 3
   

C

46
      0.027 (0.014) 0.050 (0.0015) 0.079 (0.012) 2
   

B

46
      0.097 (0.026)* 0.10 (0.019)* 0.25 (0.060)* 3
   

C

69
      0.011 (0.032) 0.034 (0.0093) 0.055 (0.039) 2
   

B

69
      0.083 (0.011)* 0.085 (0.0077)** 0.20 (0.019)** 3
   

C

92
      0.0066 (0.0007) 0.039 (0.023) 0.035 (0.017) 2
   

B

92
      0.078 (0.0067)** 0.083 (0.027) 0.18 (0.012)** 3
1996

Small

C

54
      0.23 (0.042) 0.21 (0.41) 0.95 (0.16)* 7
   

B

54
      0.23 (0.024) 0.21 (0.025) 0.78 (0.071) 8
 

Large

C

12
      0.045 (0.015) 0.040 (0.038) 0.24 (0.049) 17
   

B

12
      0.096 (0.026)** 0.091 (0.014)** 0.30 (0.080)** 17
   

C

23
      0.029 (0.012) 0.040 (0.016) 0.18 (0.051) 11
   

B

23
      0.088 (0.023)** 0.081 (0.017)** 0.27 (0.053)** 12
   

C

46
      0.011 (0.0050) 0.017 (0.010) 0.12 (0.032) 7
   

B

46
      0.081 (0.015)** 0.076 (0.017)** 0.22 (0.062)** 7
   

C

92
      0.0057 (0.0059) 0.016 (0.011) 0.11 (0.036) 6
   

B

92
      0.074 (0.017)** 0.064 (0.021)** 0.23 (0.048)** 6
1997

Large

C

12
      0.073 (0.018) 0.067 (0.017)   4
   

B

12
      0.14 (0.061) 0.077 (0.046)   4
   

C

23
      0.052 (0.023) 0.038 (0.026)   4
   

B

23
      0.14 (0.019)** 0.089 (0.012)*   4
   

C

46
      0.045 (0.024) 0.032 (0.020)   4
   

B

46
      0.13 (0.024)** 0.077 (0.018)*   4
   

C

92
      0.025 (0.010) 0.024 (0.015)   4
   

B

92
      0.12 (0.019)** 0.066 (0.013)**   4

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