Activity 2.3 Island Biogeography Simulation Report

 February 13, 2023

1.0 Introduction
Biogeography is the study of the geographical distribution of organisms such as plants and animals across space and time. In terms of biogeography, there are three main types: ecological, historical, and conservation. Each of which looks at biogeography through a different lens. Through biogeography, we are able to study species' natural patterns and behavior in order to better conserve and protect our natural environments in the future (Britannica, 2020).
Within such environments it is important to have good biodiversity. Biodiversity, or the variety of life in a particular area, plays an irreplaceable role in our life on earth as a species. It is the structure that provides us with our food, water, oxygen, and overall health (National Geographic Society, 2022). This biological diversity is composed of several different categories such as genetic diversity, species diversity and ecosystem diversity. Species diversity refers to the variety of species, while genetic diversity refers to the variation of genetic material in a given organism, and ecosystem diversity refers to the different habitats that species may occupy (American Museum of Natural History). All of these are important in biogeography in order for a population to flourish.
In this experiment, I utilized an online simulator to observe the movement of arthropod species in a temperate environment while manipulating certain variables such as island distance, island size, mortality rate, and migration rate.


2.0 Data Collection and Analysis
For this experiment, all trials were run at x8 speed for two minutes. In each trial, there are two islands and a mainland from which the species migrate. For each manipulation, two trials were recorded.


2.1 No manipulation
In this first trial no variables were manipulated. The two islands remained at 10 kilometers from the mainland and had diameters of 256 km. The migration rate remained at 2 and the mortality rate at 0.05. In the two trials performed under these criteria, the current number of species for island one was 9 in both trials one and two. Similarly, the current number of species for island two was 8 for both trials. Island one had an average of 9.1 species in trial one and 8.8 species in trial 2, while island two had an average of 9.1 in trial one and 8.6 in trial two. Both islands saw a decrease in the average number of arthropod species from trial one to trial two. For island one, the most abundant species was species 7 in trial one and species 4 in trial two, while the most abundant species for island two was species 5 in trial one and 8 in trial two. The island totals for island one were 26 in trial one and 28 in trial two, while the totals for island two were 20 in trial one and 22 in trial two.

 The images above are the collected data and an example for Trial 1 - No Manipulation from the Virtual Biology Lab Simulation (Gosnell, 2016).


2.2 Distance Manipulation
In these trials, the only manipulation that occurred was in the distance of island 2 from the mainland. Both islands remained at a size of 256 km across. Migration rate remained at 2.0 and mortality rate at 0.05. The distance of island one remained at 10 km, while the distance of island two was changed to 150 km, making island two 140 km further from the mainland. The current number of species on island 1 was 9 in both trials, and the current number of species on island 2 was 9 in trial 1 and 7 in trial 2. Compared to the trials with no manipulation, there is more variation between the distance trials’ current species. Average number of species however, was generally the same. Island 1 had an average of 8.9 species in the first trial and 8.6 in the second trial. Similarly, Island 2 had an average of 8.8 species in the first trial and 8.6 in the second trial. This shows a slight decrease from one trial to the next, but nothing significant, with the further island, island 2, having slightly less than island 1 in both trials. The most abundant species for island one were species 3 and 6 in trial one and species 3, 5, 7, and 8 in trial two, while the most abundant species for island two was species 2 in trial one and species 8 and 10 in trial two. The island total is where we start to see a more significant change. In trial 1 island one’s total was 29 while island two’s total was 16. Again in trial two, island one’s total was 20 and island two’s was 15. This means the island further away had a consistently lower island total.


 

The images above are the collected data and an example for Trial 1 - Distance Manipulation from the Virtual Biology Lab Simulation (Gosnell, 2016).


2.3 Size Manipulation
In these two trials, the size of island 2 was altered. The distance for both islands returned to 10 km, and the size of island one remained at 256 km. Mortality and migration rates stayed unchanged. The size of island two, however, was changed from 256 km to 96 km, making it 160 km smaller than island one. In trial one, the current number of species was 10 for island 1 and 2 for island 2. In the second trial these numbers changed to 6 for island 1 and 5 for island 2. In trial one there is a difference of 8, while in trial 2 there is only a difference of one, however in both, the larger island, island 1, has more species.  In trial 1, Island 1 had an average of 8.7 species and island two had an average of 2.7, and in trial two island 1 had an average of 8.8 while island 2 again received 2.7. In these trials, the larger island appears to have a larger number of species on average. The most abundant species on island 1 were species 3 and 4 in trial one and species 1, 7, 9, and 10 in trial 2. Island two’s most abundant species on the other hand were species 6 and 10 in trial one and species 4 in trial two. As far as island totals, trial one’s totals were 26 for island one and 2 for island two, while trial two’s were 10 for island 1 and 6 for island 2.  While the differences between the two totals are not the same in both trials, island one, the larger island, received a higher total each time.

 

The images above are the collected data and an example for Trial 1 - Size Manipulation from the Virtual Biology Lab Simulation (Gosnell, 2016).


2.4 Size and Distance Manipulation
In these trials, the size and distance of the islands were changed. While migration and mortality rates remained the same, island one was at a distance of 150 km with a diameter of 256 km and island two was at a distance of 10 km from the mainland with a diameter of 96 km. In trial one, the current number of species was 9 for island one and 2 for island 2. In trial two, the current number of species was 10 for island one and 3 for island two. These current numbers are different in that island one has more in both trials. As far as the average number of species, in trial one, both islands had an average of 8.7 species, while in trial two, island one had an average of 8.7 and island two, 2.4. While both islands show the same average in trial one, island two drops 6.3 from trial one to trial two, making the difference between island averages much larger in trial two. The most abundant species for island one were species 4 and 10 in trial one and species 5 and two in trial two. For island two, the most abundant species were species 1, 6, and 8 in trial one and species 1, 5, and 7 in trial two. The island totals in island one were 24 in trial one and 19 in trial two while the totals for island two were 3 in both trials. From these data we know that island one, the larger yet farther island, generally received a greater variety of species as well as a greater total.

 

The images above are the collected data and an example for Trial 1 - Size plus Distance Manipulation from the Virtual Biology Lab Simulation (Gosnell, 2016).


2.5 Migration and Mortality Manipulation
In addition to the changes made in the “distance and manipulation” trials, mortality and migration rates were changed in these trials. Island one maintained its distance of 150 km with a size of 265 km and Island two remained at 10 km out with a size of 96 km just as the previous two trials. The migration rate was changed from 2 to 4 and the mortality rate was changed from 0.05 to 0.07. In this trial, the rate of migration was changed from 2 to 4 and the mortality rate was changed from 0.05 to 0.07. In trial one the current number of species was 10 for island one and 5 for island two. In trial two the current number for island one was again 10 and island two was 4. These results are consistently different from island to island but relatively similar between trials.The average number of species in trial one was 9.4 for island one and 3.4 for island 2. Again in trial two, the average was 9.4 for island one and 3.6 for island 2. These results show that the average species for island one are exactly the same from trial one to two and the average for island two only decreases by a difference of 0.2. The most abundant species for island one was species 8 in trial one and species 5 and 9 in trial 2. As for island two, the most abundant species were 2 and 4 in trial one and 10 in trial 2. In trial one the island totals were 37 for island one and 7 for island two, while in trial two island one had a total of 32 and island two had a total of 5. These trials show the most dramatic gap in totals between islands by far.


 

The images above are the collected data and an example for Trial 1 - Migration and Mortality Manipulation from the Virtual Biology Lab Simulation (Gosnell, 2016).


3.0 Discussion
From the above data, it is evident that generally, the larger islands received more species, as well as a greater island total. In addition, having a larger diameter as well as being closer to the mainland both increased the island totals and species, however it would seem that island size has a greater impact than distance. This is seen in trial 2.2 Distance Manipulation and 2.3 Size Manipulation. The island totals in the distance manipulation trials more clearly resemble those of the trials with no manipulation.
The largest changes, however, are seen in the last trials where migration and mortality rates were changed. Increasing the migration rate allowed for the most prosperous species survival. Specifically, island one in 2.5 Migration and Mortality Manipulation had the highest island totals overall. This island had a size of 256 km and was placed 150 km from the mainland, in addition to a migration rate of 4 and a mortality rate of 0.07.
The distance trials, however, resulted in the most species diversity, having ten different most abundant species.

The image above is the collected data in a pie graph for Manipulation 4


4.0 References 

American Museum of Natural History. (n.d.). What is biodiversity? why is it important?: AMNH.  https://www.amnh.org/research/center-for-biodiversity-conservation/what-is-biodiversity

Britannica, T. Editors of Encyclopedia (2020, January 9). biogeography. Encyclopedia Britannica. https://www.britannica.com/science/biogeography
 

Jones, T. C., Hiatt, A. C., Emma, T., Mains, A. R., Kiser, K., & Ford, D. (2016). Virtual biology lab [Computer software]. East Tennessee State University. http://virtualbiologylab.org/ModelsHTML5/IslandBiogeography/IslandBiogeography.html
 

National Geographic Society. (2022, May 20). Biodiversity. National Geographic. https://education.nationalgeographic.org/resource/biodiversity