Worksheet #11 - Species Interactions -Barnacles

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University of British Columbia *

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121

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Geography

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Feb 20, 2024

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pdf

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1 SPECIES INTERACTIONS: WORKSHEET ACTIVITY 1. What are some factors that might determine whether a species can live in the upper intertidal zone? List at least three: - Survive changes in moisture - Survive changes in temp - Withstand strong waves - Survive changes in salinity 2. The figure below shows the overlap in fundamental niches (i.e., what range of the intertidal zone they are able to inhabit when alone) for the two species of barnacle. a. How do the fundamental niches of the two species differ? (Compare/contrast the curves in terms of their ranges): - Species 2 occupies a larger niche than species 1. It also pushes much further into the niche of species 1 than 1 does into 2. b. Imagine Chthamalus sp. (Species 2) is the only species present on a particular beach. What sorts of predictions can you make about the relative fitness of Chthamalus sp. individuals living in different regions of the intertidal? What specific factors might influence individual fitness in this population? - The specific factors that might influence its fitness would be the environmental factors in the upper vs lower parts of the intertidal regions. Most likely the ones in the upper region would need to be hardier to withstand the temp and water level changes. As well as the constant waves. I feel like it would be easier for the lower barnacles would be able to get food easier. b. Now imagine that both Semibalanus sp. (Species 1) and Chthamalus sp. (Species 2) are found together on the same beach. What sorts of predictions can you make about the fitness of Chthamalus sp. individuals living in different regions of the intertidal when Semibalanus sp. individuals are also present? - The fitness of the chthamalus that are not present in the same niche as the semibalanus would have a higher fitness because they do not have to cooexist. They have more access to food resources
2 because they are not competing. They also have as much space within their niche to reproduce and spread out. 3. Assume Species 1 is a stronger competitor than Species 2 (i.e., if the two species are directly competing for the same resource, Species 1 is more likely to “win”). What might the intertidal distribution of the two barnacle species look like when they are found in the same area? Draw your prediction below. 4. Imagine that we removed all of the Species 2 ( Chthamalus sp.) individuals from the beach. After removing Species 2, would you expect Species 1 ( Semibalanus sp.) to colonize the upper intertidal zone soon after? Explain why or why not. - I would to some extent. If they are able to inhabit and survive the upper zone, then with their only competition gone they are free to spread out and reproduces on all regions of the intertidal zones. 5. Imagine that several 100s of years later, Species 1 ( Semibalanus sp.) is in fact found to be colonizing the upper intertidal zone. What series of events must have occurred to allow this? - A mutation must occur to allow the species to inhabit the abiotic zone. - It would need to occur in a gamete - Individual with mutation must reproduce - Larvae with mutation would need to be transported to the upper zone - Natural selection would need to select for that specific trait
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