You are studying two species of manakins, a small and colorful tropical bird species. One species, the white-ruffed manakin (Corapipo leucorrhoa) is found in lower elevation lowland forest, where it has a population of approximately 150 individuals, and t
You hypothesize that the two bird species are competitors, and that the higher-elevation species is the inferior competitor but is more able to withstand the colder temperatures higher up on mountains.
(a) To test your hypothesis, you set up large experimental enclosures (cages) at high and low eleva- tions. At each elevation there are three types of cages: 20 white-ruffed manakins, 20 white-crowned manakins, and both species together (20 of each) in an enclosure (for a total of six treatments). At the end of the one breeding season, you come back to your enclosures and see how many individuals are present.
Sketch a barplot of the results you would expect in high elevation (left plot) and low elevation (right plot) if your hypothesis is supported.
(b) Explain your answer above. How do those results support your hypothesis?
(c) You then used a niche model to predict how the two species’ ranges will change with higher temperatures due to climate change. On the empty diagram below, mark the new predicted range for each species. Then explain your answer below. (4 points)
(d) Finally, you couldn’t resist using a Lotka-Volterra model to model competition of these two bird species. Use the information in the question above, and assume that the white-ruffed manakin (Corapipo leucorrhoa) is species 1. Also assume α12 = 1 and α21 = 0.5. Draw your isoclines on the plot below. If you start with 50 individuals of each species, what will happen? Use the isoclines to draw your predicted trajectories on your plot as well. (6 points)
Sample Solution
