Population Dispersion of Spider Webs

1. Population Dispersion of Spider Webs

2. Spinnerets Webs to catch food Draglines Webs vs. Burrows Ballooning Living conditions Common Names Nesting Eggs Life cycle Spiders www.biologymad.com www.amonline.net www.ext.colostate.edu

3. Spider Species Sheet-web weavers Orb Weavers

4. Data Collection • Jewell Moore Nature Reserve • Random directions from central point • 1 meter radius circles • Limited to Forest • Count # of webs in trees

5. DataMean= 1.233 Variance=1.840SD=1.357 Table 1

6. Results • In the Jewell Nature Reserve we surveyed thirty plots and found 37 spider webs, averaging 1.23 webs per plot. • We expected 4 plots to contain 0 spider webs, but found 11 (see Table 1). • The chi-square value, 43.28, suggests a borderline random, contagious dispersion pattern (refer to Figure 4C.6 in lab manual). • Our variance to mean ratio, 1.46, is somewhat close to 1 which suggest random dispersion, but it is also above one which suggest contagious dispersion. This is consistent with our chi-square value. • The number of individuals found in all the plots were close to the number of individuals predicted by Poisson which suggest random dispersion (see Table 1 and Figure 1).

7. Figure 1

8. Conclusion • Why might our data be borderline between random and contagious? • Old webs • Different species

9. Conclusion • Main Hypothesis: 1. The spider webs will be randomly dispersed because of food competition. • Alternative Hypothesis: 2. Randomly dispersion occurs to prevent cannibalism. (see text page 253) www.amonline.com