Activity 2.3: Island Biogeography Simulation Report

1.0 Introduction

Biogeography is an area of study within the field of biology. In its simplest terms, it's the study of the distribution of plants and other wildlife across the globe; however, there is much more to it than that. Biogeography is the study of closely examining the natural occurring patterns and processes within Earth's biosphere, and figuring out how those specific developments came to be. The subject of this report, island biogeography, is a section of biogeography that is key in studying these phenomena. 

The video, "Theory of Island Biogeography" (Quantumwombat, 2015), describes island biogeography as a concept that explains species diversity on islands, with islands being classified as any area of land that has distinct characteristics differing from its surrounding area. The 'Theory of Island Biogeography' was "first published by McArthur and Wilson, during a study about pacific birds. They found that larger islands such as Sumatra, Borneo, and Papua had about 700 species of birds present, while smaller islands such as the Christmas Islands only had about 10 species" (Quantumwombat, 2015). They attributed this natural occurring phenomena of species migration to a variety of factors, with the most important being the island's size/area and it's distance from the mainland. 

Effects of size and distance from the main source of colonizers (Summers, 2019).

This research report is based off of experimentation using simulations that closely replicate the real-life processes that occur in these specific conditions. Through my own research, I was able to put MacArthur and Wilson's 'Theory of Island Biogeography' to the test and determine whether or not it holds true. The following are my findings. 

2.0 Data Collection and Analysis

Within this section of my report, I explain the research process I used, the data I managed to collect, and my analysis of the data.

For this experiment, I used the Virtual Biology Lab Island Biogeography Simulator (Jones et al., 2016) to run 5 different simulations, each with 2 trials a piece, examining the migration of reptilian species to islands in a tundra-like climate. The different manipulations were as follows: (1) no manipulation, (2) distance manipulation, (3) size manipulation, (4) size plus distance manipulation, and (5) migration and mortality manipulation. 

*Note: each manipulation examined two separate islands and was run for two different trials, with each trial being two minutes in duration. 

The data I collected was all recorded using a Google Spreadsheet, with the information collected being as follows: current # of species, average # of species, top two most abundant species, island total # of inhabitants, distances of island 1&2 from the mainland, sizes of island 1&2, mortality rate, migration rate, habitat type, and taxon of species. 

To more specifically explain the procedures and processes of the experiment, each manipulation was conducted examining two islands. Two 2-minute trials were run for each manipulation and, at the end of each trial, the desired data (mentioned previously) was documented. Each manipulation followed the same experimental procedures as one another; however, each manipulation varied from the next due to a change in a specific variable that was made at the beginning of each trial. The variable changed was either the size of one or both of the islands, the distance of one or both of the islands, the rate of mortality, or the rate of migration of species. The rest of this section will be attributed to a more in-depth examination of each experimental manipulation. 

2.1 Manipulation- No Manipulation (Baseline)

For this manipulation, two separate 2-minute trials were conducted with all variables being left unchanged at the standard experimental values. Both islands 1&2 were set at a distance of 10km away from the mainland, and 256km in size. The mortality and migration rates were set at baseline values of .5 and 2 respectively. 

Trial 1 of the experiment recorded the current # of species as 7, for island one and 5, for island two. The average number of species was 7.9, for island one and 8, for island two. The most abundant species were species 1 and 5, for island one, and species 3, for island two. The island total for island one was 13 and for island two it was 8. 

Trial 2 of the experiment recorded the current # of species as 10, for island one and 7, for island two. The average number of species was 8.1, for island one and 7.4, for island two. The most abundant species were species 1 and 10, for island one, and species 3, 4, and 7, for island two. The island total for island one was 19 and for island two it was 15.

Based on the data collected, when each of the islands are left at the same baseline experimental values, there appears to not be much variation within their experimental data. The current and average # of species, as well as their island totals, were at similar values to one another throughout both trials. However, there did seem to be some variation in the most abundant species. During both trials, islands one and two appeared to have completely different abundant species. For island one, those species were 1, 5, and 10. For island two, they were species 3, 4, and 7. This was one only major experimental difference between the two, but based on the recorded data, there doesn't seem to be a clear factor to attribute this change to. 

2.2 Manipulation- Distance Manipulation

For this manipulation, two separate 2-minute trials were conducted with most variables being left unchanged at the standard experimental values, with the exception of the distance of island 2. Island 1 was set at a distance of 10km away from the mainland while island two was set at a distance of 50km. Both islands were 256km in size. The mortality and migration rates were set at baseline values of .5 and 2 respectively. 

Trial 1 of the experiment recorded the current # of species as 8, for island one and 8, for island two. The average number of species was 7.8, for island one and 8.2, for island two. The most abundant species were species 5, for island one, and species 3, 5, and 6, for island two. The island total for island one was 15 and for island two it was 16. 

Trial 2 of the experiment recorded the current # of species as 6, for island one and 9, for island two. The average number of species was 5.7, for island one and 6.7, for island two. The most abundant species were species 9, for island one, and species 1, for island two. The island total for island one was 10 and for island two it was 17.

Based on the data collected, there appears to not be much variation within their experimental data. The current and average # of species, as well as their island totals, were at similar values to one another throughout both trials. However, there did seem to be some variation in the most abundant species. During both trials, islands one and two appeared to have mostly different abundant species. For island one, those species were 9. For island two, they were species 1,3, and 6. However, unlike the previous manipulation, this time both islands had a common abundant species in species # 5. This was one only major experimental difference between the two, but based on the recorded data, there doesn't seem to be a clear factor to attribute this change to. 

2.3 Manipulation- Size Manipulation

For this manipulation, two separate 2-minute trials were conducted with most variables being left unchanged at the standard experimental values, with the exception of the size of island 2. Island 1 was set at a size of 256km while island two was set at a size of 128km. Both islands were set at a distance of 10km away from the mainland. The mortality and migration rates were set at baseline values of .5 and 2 respectively. 

Trial 1 of the experiment recorded the current # of species as 7, for island one and 3, for island two. The average number of species was 7.8, for island one and 3, for island two. The most abundant species were species 1 and 5, for island one, and species 1, 6, and 10, for island two. The island total for island one was 13 and for island two it was 3. 

Trial 2 of the experiment recorded the current # of species as 8, for island one and 3, for island two. The average number of species was 8, for island one and 3.3, for island two. The most abundant species were species 2, for island one, and species 2, for island two. The island total for island one was 12 and for island two it was 5.

Based on the experimental data collected in this manipulation, there was some major variation between the two in almost every recorded value. Unlike the last two manipulations, island one's values for current # and average # of species were much greater than that of island two's. Island one appeared to have a much greater island total than island two as well, with the sum of both trials for island one being 25, and island two being 8. However, even though this manipulation had the greatest variation compared to the other manipulations, it had the least amount of variation in species abundance. Unlike the other manipulations, island's one and two shared more abundant species than the others. Island one had different abundant species in species 5, while island two had them in species 6 and 10; however, both islands shared species 1 and 2 in abundance. Looking at the data, it can be inferred that the size of the island plays a factor in the number of species on an island, but in regards to the specific abundance of species, there doesn't seem to be a clear indicator as to what causes the variation. 

2.4 Manipulation- Size plus Distance Manipulation

For this manipulation, two separate 2-minute trials were conducted with most variables being left unchanged at the standard experimental values, with the exception of the size and distance of island 2. Island 1 was left at the baseline value of 10km away from the mainland and 256km in size. Island 2 was changed to a value of 410km away from the mainland and 64km in size. The mortality and migration rates were set at baseline values of .5 and 2 respectively. 

Trial 1 of the experiment recorded the current # of species as 8, for island one and 0 for island two. The average number of species was 8.2, for island one and 0, for island two. The most abundant species were species 7, for island one, and there were no abundant species, for island two. The island total for island one was 18 and for island two it was 0. 

Trial 2 of the experiment recorded the current # of species as 6, for island one and 0 for island two. The average number of species was 6.6, for island one and 0, for island two. The most abundant species were species 8, for island one, and there were no abundant species, for island two. The island total for island one was 7 and for island two it was 0.

Based on the experimental data, this manipulation had the greatest variation among all of the manipulations so far. Since island one's experimental values weren't altered, the numbers from both trials are similar to those of previous manipulations; however, with the size and distance of island two being changed, its values are much different in comparison. For this manipulation, island two appeared to have no life/species occupying it whatsoever, indicating that the combination of island size and distance away from the mainland plays a huge part in whether or not species will live on the island. The abundant species for island one this manipulation were species 8 and 7, offering no specific correlation to that of the previous manipulations. 

2.5 Manipulation- Migration and Mortality Manipulation

For this manipulation, two separate 2-minute trials were conducted with most of the experimental variables being changed from their standard values. Island 1 remained at the baseline values of 10km away from the mainland and 256km in size. Island 2 was changed to a value of 150km away from the mainland and 192km in size. The mortality and migration rates were changed to values of .1 and 5 respectively. 

Trial 1 of the experiment recorded the current # of species as 8, for island one and 7, for island two. The average number of species was 8, for island one and 5.7, for island two. The most abundant species were species 5, for island one, and species 1 and 10, for island two. The island total for island one was 17 and for island two it was 9. 

Trial 2 of the experiment recorded the current # of species as 9, for island one and 8, for island two. The average number of species was 7.9, for island one and 6.2, for island two. The most abundant species were species 5 and 8, for island one, and species 3, 4, 5, and 6, for island two. The island total for island one was 16 and for island two it was 13. 

Based on the data collected, there appears to not be much variation within their experimental data. The current and average # of species, as well as their island totals, were at similar values to one another throughout both trials. However, there did seem to be some variation in the most abundant species. During both trials, islands one and two appeared to have mostly different abundant species. For island one, those species were 8. For island two, they were species 1, 3, 4, 6, and 10. However, unlike the previous manipulation, this time both islands had a common abundant species in species # 5. This was one only major experimental difference between the two, but based on the recorded data, there doesn't seem to be a clear factor to attribute this change to. 

 3.0 Discussion

4.0 References

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

        Quantumwombat. 2015, November 13). Theory of Island Biography [Video].                                            YouTube. https://www.youtube.com/watch?v=5PyrRtSytmM

        Summers, E. E. (2019). Landscape ecology [Slide presentation]. SlidePlayer.                                             https://slideplayer.com/slide/15739557/

Links