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Scientists have found a difference in the percentage of fruit in the diet of primates, including lemurs, in several locations around the world. They wondered if it was associated with the nitrogen content of the fruit. To answer this question, they determined the nitrogen content of fruits in three locations; Madagascar, the New World, and the Old World.

Note: Pineapple is the national fruit of Madagascar.

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The resulting data is displayed as parallel boxplots on the next slide.

Data are consistent with research findings.

Each location produces many types of fruits. Nitrogen data is represented as a percentage of dry matter. That means the scientists first dehydrated each fruit in their sample and then calculated the percentage of the dried matter that was nitrogen.

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a) Describe the differences in the distributions of the nitrogen level in fruits for Madagascar and the Old World.

These data are modified from, and consistent with, data in: Scientific Reports | 7: 14406 | DOI:10.1038/s41598-017-13906-y. They are estimates for educational purposes and should not be used as a substitute for the original data.

Percent of nitrogen in fruits

Note: Old World usually refers to African and Asian countries.

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b) Frugivory is the practice of including fruit in a diet. Primates have diets that consist of vegetation, insects, and fruit. An essential component for all life is nitrogen. Which area would require primates to supplement their diet with more leaves and insects. Explain.

These data are modified from, and consistent with data in: Scientific Reports | 7: 14406 | DOI:10.1038/s41598-017-13906-y. They are estimates for educational purposes and should not be used as a substitute for the original data.

Percent of nitrogen in fruits

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c) Climate change can result in a mismatch where pollinators are not available at the time flowers are ready for pollination. This would reduce the amount of fruit available for primates. Using the boxplots to the left, predict the location that would be most affected by this change and justify your answer.

These data are modified from, and consistent with data in: Scientific Reports | 7: 14406 | DOI:10.1038/s41598-017-13906-y. They are estimates for educational purposes and should not be used as a substitute for the original data.

Average proportion of fruit in primate diets

The average proportion of fruit in primate diets from 62 sites across the 3 areas.

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Solutions and Scoring

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Solution: part (a)

Madagascar fruit has a lower nitrogen concentration than Old World fruit. All of the tested fruit in Madagascar, except for one high outlier, had a nitrogen content below the median of the Old World distribution. In addition, the Madagascar distribution of nitrogen levels has a smaller IQR and range than the Old World distribution. This means the fruits in Madagascar consistently have lower nitrogen levels. The distribution of nitrogen levels in the Old World has a large range including 3 high outliers. Fruits in the Old World vary significantly in their levels of nitrogen.

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Scoring: part (a)

1 pt: A clear comparison of position or center

Such as: The median of the Madagascar distribution, approx. 0.8%

is less than the median of the Old World distribution, about 1.40%.

OR

Madagascar fruit has a lower nitrogen concentration than Old World fruit.

1 pt: A clear comparison of variation (IQR or range)

Such as: The nitrogen in Madagascar fruit varies less than the nitrogen

in Old World fruit.

1 pt: A comment on the outliers

Such as the Old World distribution has three very high outliers which is

more outliers than the Madagascar distribution.

1 pt: Context including the word nitrogen.

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Solution: part (b)

Primates in Madagascar would need to supplement their diets with more leaves and insects. The fruit in Madagascar clearly contains less nitrogen than the other two areas. The entire distribution (except for the one high outlier) is lower than the median nitrogen value in the other two areas. Primates in both the New World and Old World have access to fruits with high nitrogen levels.

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Scoring: part (b)

1 pt: Madagascar is chosen

1 pt: A justification is made based on the lower values in

Madagascar compared to the other two areas

1 pt: Context including the phrase “percent of nitrogen”.

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Solution: part (c)

The New World would be most affected. Fruit makes up approximately 50% of the diet of the New World primates. This is higher than the other two locations.

Neither Madagascar nor the Old World has primates with percentages of fruit in their diet that high based on the much lower medians and third quartile.

New World primates would suffer a much greater loss to their diet if fruit was not produced due to a lack of pollination. Primates in the other areas are already accustomed to eating much more vegetation and insects.

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Scoring: part (c)

1 pt: The New World is chosen

1 pt: A justification is made based

on the higher values in the

distribution of the proportions

of fruit in the New World

primate diets compared to

the distribution of proportions

in other two areas.

1 pt: Context including the phrase

--fruit in primate diets.

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Citation

Donati, G., et al. (2017). Low levels of fruit nitrogen as drivers for the evolution of Madagascar’s primate communities. Scientific Reports. 7: 14406. DOI:10.1038/s41598-017-13906-y