Do you drink coffee? A lot of people do—coffee is a major tropical crop, valued at over \$100 billion per year. The most popular species of coffee, Coffea arabica, originated in Africa and is now planted extensively in Central and South America. The pest called the coffee berry borer beetle (Hypothenemus hampeii) moved along with the coffee and is a major problem for coffee farmers, sometimes destroying half of the coffee crop in mature plantations.
Pesticides are generally ineffective in killing coffee berry borers. Ecologist Daniel Karp and colleagues conducted a study in Costa Rica to determine if natural predators like birds reduce the beetle population. The researchers selected 12 control plots and used nets to exclude birds from 12 similar treatment plots. What is the take-home message of the graph? (Remember, * means P < 6 0.05)

Verified step by step guidance

1. Examine the graph to understand the variables being compared. The y-axis represents the percentage of berries with borers, while the x-axis distinguishes between plots before and after exclosure nets were installed.
2. Identify the two groups in the study: control plots (where birds were not excluded) and treatment plots (where birds were excluded using nets).
3. Observe the data for the 'before' condition. Both control and treatment plots have similar percentages of berries with borers, indicating no significant difference before the nets were installed.
4. Look at the 'after' condition. The treatment plots, where birds were excluded, show a higher percentage of berries with borers compared to the control plots. This suggests that excluding birds leads to an increase in borer infestation.
5. Note the asterisk (*) above the bars in the 'after' condition, indicating a statistically significant difference (P ≤ 0.05) between the control and treatment plots. This implies that birds play a significant role in controlling the coffee berry borer population.

Key Concepts

Ecological Interactions

Ecological interactions refer to the relationships between organisms and their environment, including predator-prey dynamics. In this study, the interaction between coffee berry borer beetles and their natural predators, such as birds, is crucial. Understanding these interactions helps in assessing how the presence or absence of predators can influence pest populations and crop health.

Experimental Design

Experimental design is the framework for conducting scientific research, ensuring that results are valid and reliable. In this study, researchers used control and treatment plots to compare the effects of excluding birds on the coffee berry borer population. This design allows for a clear understanding of how the presence of birds impacts pest levels, providing insights into effective pest management strategies.

Statistical Significance

Statistical significance indicates whether the results of an experiment are likely due to chance or represent a true effect. The asterisk in the graph suggests that the difference in the percentage of berries with borers between control and treatment plots after the nets were installed is statistically significant (P < 0.05). This implies that excluding birds had a meaningful impact on reducing the beetle population, which is critical for interpreting the study's findings.