Download ISLAND BIOGEOGRAPHY – OPPOSING PROCESSES OF

Pacific Island Biogeography
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ISLAND BIOGEOGRAPHY – OPPOSING PROCESSES OF MIGRATION & EXTINCTION
Island Biogeography
Ecologists have long noted that islands, particularly those far from continents are naturally
depauperate of species relative to nearest land masses (to continental areas with similar
climate/vegetation) and that smaller islands in the same group of islands (so the same distance from
continents) are additionally impoverished. These general observations are the basis for Island
Biogeography theory which attempts to explain these pattern based on ecological principles. In this
exercise, we will explore this theory – evaluate its conclusions, test its validity under one
circumstance, and discuss the consequences for conservation.
A. Island Biogeography and Biodiversity Simulation. Setup and run the Equilibrium Theory of
Island Biogeography Model ISLAND1.EXE to explore what this theory says about processes
affecting island biodiversity. (Only works on Windows platforms.)
1. Extract the zipped files onto your machine.
2. Place the extracted ISLAND1.EXE and *.dll files to the same folder.
3. The model is a Windows95/NT executable: to run, 1st right click the .exe file, select
Compatibility tab, and set the operating system to Win95.
4. Run the model & address the worksheet questions —
Questions for discussion –
1) According to the model, what sorts of islands would you expect to have the highest species
numbers? The lowest? Why? – what ecological processes play a role in determining the species
richness of an island’s biota?
2) What are the limitations of this model in comparing the diversity of different islands? What
processes are lacking in the model?
3) Does this model seem more accurate for particular types of organisms than others? List some of
both.
B. Island Biogeography of the Pacific Islands
In this exercise, we will use bird checklists to evaluate relationships between species richness (# of
spp) and island geography for the Polynesia/Micronesia Hotspot. Island-by-island checklists are
available in A Field Guide to the Birds of Hawai’i and the Tropical Pacific, as are maps showing
island size and position in the Pacific. Google Earth or an atlas will be handy for determining
distances from large land masses.
TKittel 3/10,3/11
Pacific Island Biogeography
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Follow these steps:
1) State clearly the questions you want to ask.
2) Construct a dataset organized by island (and by island group) of:
a) Land bird species richness –
i) Exclude sea-faring birds, aquatic birds (those preceding Rock Dove in lists)
ii) Exclude obvious introduced species (e.g., Rock Dove)
iii) Include residents (‘R’) and extirpated (‘X’)
b) Distance from closest major land masses (continents and ‘continental islands,’ such as New
Caledonia) – in km. In GoogleEarth, use the Ruler tool. Evaluate distances to possible
major land masses.
c) Island size – area in km2. May have to measure island axes to calculate as area of an ellipse
Enter the data in the file “Ex…template-BirdIslandBiog_310r.xls” Table layout is:
Island group:_____________
Island (same order in list)
Distance (km)*
*1 miles=1.6 km
Size (km2)**
#Residents (Native, R&X's)
**1 acre=0.00405 km2
You may find you’ll have to make decisions to determine island size and distance (e.g., the list
combines bird lists across some small island groups). Keep track of these assumptions as they
may influence your results, and so may come up in your discussion of results.
3) Plot the results in a manner that reflects your questions. We’ll also compare the results across
island groups as a class (enter into the spreadsheet: Ex…_template-BirdIslandBiog_310.xls)
Questions for discussion –
1) Do the data you’ve assembled support the basic tenets of Island Biogeography theory? If not,
which one of the two relationships is stronger?
2) If the theory is not well supported for your island group, can you think of reasons why it doesn’t
hold up under these circumstances?
3) Based on your results, what are the consequences of these islands’ regional geography for bird
conservation in this hotspot?
TKittel 3/10,3/11