1. SKETCH or MAP the experimental design that is explained in the Methods sectio
ID: 105568 • Letter: 1
Question
1. SKETCH or MAP the experimental design that is explained in the Methods section.
2. Interpret (in your own words) how the data were analyzed statistically.
3. Interpret Figure 1 – What results were significant and how do you know? What was their values that were cited as a means to compare with their P-values?
This is the result section
Here is the link of the journal article if the pictures are bad : http://onlinelibrary.wiley.com/doi/10.1002/ecy.1732/full
Methods Study site and species This study was conducted off the leeward coast of Bonaire, Dutch Caribbean (12°9'13.01" N, 68 16'42.79" W), an oceanic island that is surrounded by a continuous fringing reef. Red lionfish Pterois volitans), first sighted in Bonaire in 2009 (Schofield 2010), were used as the invasive predator for all experiments. Lionfish consume a wide range of native fishes, with recruit-sized fishes being particularly vulnerable to lionfish predation (Albins and Hixon 2008). Graysby grouper (Cephalopholis cruentata and French grunt (Haemulon flavolineatum were used a native species for comparison with invasive lionfish. Graysby grouper are ecologically similar to lionfish and also consume a high proportion of small recruit fishes (Randall 1967, Stallings 2008 whereas French grunt consume primarily small crustaceans (Randall 1967) In order to measure recruitment to reefs that differ only in the presence of predators, 15 standardized reefs were constructed halfway between the shore and the coral-reef crest on an approximately 55 m wide and 5 m deep sand flat. Each reef measured 80 x 60 x 15 cm, and consisted of dead coral rubble placed inside of stainless steel wire baskets. The reefs were placed in three groups (statistical blocks) separated by approximately 17 m, with each block containing five reefs spaced approximately 3 m apart (Appendix S1; Vail and McCormick 2011)Explanation / Answer
1. Experimental study and design: There were 15 reefs constructed in the middle of the shore and the coral reef crest on a sandflat which was 55 m wide and 5m deep. The dimensions of each reef were 80*60*15 cm. There were dead coral rubble placed between the stainless steel wire baskets. The reefs were divided into three groups with distance of separation between each group was 17m and there were about 5 reefs in each group and the distance of separation between each reef were 3m.
2. The sampling days in which there were extremely low recruitmnent i.e. when the recruits for any block were less than the number of coral reefs( less than 5 individuals per species) were excluded in the analysis process. For damselfish the number of sampling days in July were 14, 6 for snapper. During August, the number of sampling days for both species were 7. Besides that, in the first experiment there were 4 days that had extremely high recruitment of damselfish and were 2 days in the second experiment in which the recruitment for snapper were extremely high.
For the analysis daily counts of recruits were changed into proportions of individuals on each reef out of the total number of recruits for that particular species within each reef block. For this generalised linear models which uses the quasibinomial and the logit link function were run. These measure each proportion on the basis of sample size. To determine whether there is any effect of predator treatment with recruit density, the effect of treatment*conspecific recruit density were calculated for each experiment. Also when the interaction term was significant post hoc pairwise comparison tests were conducted. Whereas when the interaction term was not significant this was excluded from the experiment and only effect of predator treatment across all recruit densities were conducted.
3. There were almost equal recruitment of damsel fish to all the reefs irrespective of predator treatment and conspecific density. eg treatment* density X2=2.44, P=0.65 and treatment X2=3.79, P=0.43.
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