MacArthur and Wilson II: Archipelagos

Last weekend, my post outlined MacArthur and Wilson's Theory of Island Biogeography for one island. Recall that we discussed on how islands gained species, through colonization, and how they lost species, through extinction.

But islands often occur as part of an archipelago, a collection of islands. Islands in the archipelago vary in a number of ways, including topography, shape, size, and distance to the mainland. MacArthur and Wilson focused on the effect that two characteristics affect diversity: distance between the island and the mainland, and island size.

Island Biogeography & the Channel Islands

E. O. Wilson (top)
Robert H. MacArthur
(below)
(from bioquest.org)

I anticipated posting this weekend about how species get to islands. I will get to that, but I thought that first I should talk about island biogeography. When I was first introduced to this model of island biogeography, I was fairly baffled. I didn't get the swooshing lines. I didn't understand why their intersection was interesting. Over the years, I've had to teach about the model to undergraduates, as both a graduate student and a faculty member. As soon as I understood it, it became one of my favorite concepts to teach!

The Theory of Island Biogeography, published by Robert H. MacArthur and Edward O. Wilson in 1967, is a classic ecological model of island biodiversity. An abbreviated explanation of this model was in the most recent Catalina Island Conservancy online newsletter.

History of Islands: Connection and Isolation

Catalina Island

Not all islands are created equal.

You can't tell at first glance, but the history of an island is one of the key factors that affects biodiversity on the island.