Lionfish Invasion: Density-Dependent Population Dynamics

Fruit production in paprika peppers

Red and green paprika peppers in a container surrounded by more peppers
A woman in a field of peppers holding several paprika peppers in her hands.

Paprika pepper (Capsicum annuum var. annuum L.) is a plant that is commonly grown for its fruits, which are dried and ground up to make the spice paprika. Cavero and colleagues (2001) wanted to know what factors affect a pepper plant’s yield, which is the total dry weight of the fruits it produces. A plant’s fruit yield is a measure of the reproductive output of an individual.

The scientists planted paprika pepper seeds and let them grow for one month. They then removed some of the plants to create 10 groups with different densities, which ranged from 13,333 plants per 10,000 m2 to 533,333 plants per 10,000 m2. Six months later, the scientists picked the fruits from a small section of each group. The fruits were counted, dried, and weighed to determine the fruit yield per plant — as well as the overall yield of all plants within 10,000 m2 — for each of the 10 groups.

The effect of density on the yield (total dry weight of the fruit produced) of pepper plants over one year

Each point represents the mean of four replicates at a given density. The error bars show ±1 standard deviation.


The x axis of the graph is labeled Plant density in 1000 plants per 10,000 square meters and ranges from 0 to 600 in increments of 100. On the left hand side of the graph, the y axis is labeled Yield in grams per plant and is represented by a dotted blue line with blue squares ranging from 0 to 7 in increments of 1. On the right hand side of the graph, the y axis is labeled Yield in tons per 10,000 square meters and is represented by a solid red line with red circles ranging from 0 to 250 in increments of 50. The blue box line starts at about 4.5 when plant density is lowest and decreases gradually until it reaches less than 1 at a density of 200 and levels off to near zero when the density reaches 600. The red circle line starts near zero when plant density is lowest and rises sharply until density reaches about 125, then levels off at about that same number until density reaches 600. There are error bars on most of the points.

Use what you've learned above to answer the following questions:

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