Discussion
Introduction Materials and Methods Graphs and Tables Results
Discussion Background Information Pictures References

           The results of the study show us that middle elevation contains a greater density of hermit crab shells, with more species diversity, than low elevation with over half the population consisting of morula and costanachis. The morula and costanachis species were grouped together due to time constraints in counting, and the high number of both species. It was also determined that the type of rock type has no effect on hermit crab shell species. There was a slight difference of 14 more shells collected under total basalt rocks compared to total coquina rocks. The reason for such an increase in number of shells found in middle elevation compared to low elevation may be because of an abiotic factor in zone 4 of the intertidal. One possible reason for the low numbers of crabs in low elevation may be due to stress caused by turbulence of breaking waves on that zone. The location of hermit crabs is important because their location correlates with biodiversity of other marine animals or potential predators to the crabs. This is not very surprising, as this is the norm of most ecosystems.
            Our initial predictions had more to do with texture and color of shells, and our results focused on species. This is because before the study, not enough information about hermit crab shells was known to make an educated guess on the amount, diversity and location of shell species. While collecting shells, we changed our initial questions slightly, to accurately fit what we were finding. We also found that shells species did not range very much in color or texture. The Chi squared test indicated that the difference in shell selection is statistically significant. With a p-value of less that .001 with 12 degrees of freedom, the critical value is 32.91. With an experimental Chi squared value of 424.889, the null hypothesis can be rejected. Given the result of the Chi squared test, there is a significant difference between the numbers of hermit crabs found in two different elevations.

 

Possible Follow up Questions:

1. Is the preference for shells in the middle elevation intertidal zone the same on CEDO Beach as on Station Beach, or any other beaches outside of Rocky Point?

2. What is the reason for such a high abundance in the Morula and Costanachis species?

3. How would the results have varied if the collection was increased; in terms of rock types and diversity of shell species?

 

Authors: Jenessa Hill & Jennifer Mordaunt| Ecology 450| Marine Discovery| Created November 20,2007| University of Arizona| Class photos