Insular biogeography

Some places are like islands.

They are small and cut off from other lands. This can happen in the ocean. It can also happen on mountain tops.

Big islands have many kinds of life. Small islands have fewer kinds. This is because big islands have more room. They also have more types of homes for animals. Distance matters too. Islands close to land get more new visitors. Faraway islands get fewer visitors. This helps us learn how to save animals.

We can protect large areas to keep many species safe.

Some places act like islands. Scientists call this island biogeography. It is the study of how life lives in isolated spots.

An island can be land in the sea. It can also be a mountain peak or a small forest. These spots are surrounded by places where those living things cannot survive.

Two scientists named Robert MacArthur and E. O. Wilson started this study. They found that two main things decide how many species live in an island. The first is immigration. This is when new species move to the island. The second is extinction. This is when species die out.

Distance from the mainland is very important. Islands close to the mainland get more new visitors. Faraway islands get fewer visitors.

Size also matters a lot. Large islands have more room and more types of homes. This helps prevent extinction. Large islands can also act as a target for new species. This is called the target effect. In the end, the number of species finds a steady balance.

Scientists study how life lives in isolated places. This field is called insular biogeography. An island is any habitat surrounded by a place where those living things cannot survive.

While we often think of land in the ocean, an island can be many things. It could be a mountain peak or a small patch of forest. It might even be a park surrounded by busy roads and houses. These isolated spots are very important for understanding how species change over time.

Two main forces decide how many species live in these places. The first is immigration, which is when new species arrive. The second is extinction, which is when species die out.

Distance plays a huge role in this process. Islands close to a mainland receive more visitors than far ones. This is called the distance effect. Size also matters through the species-area effect. Large islands have more room and many different types of homes. This makes it harder for species to go extinct by chance.

In the 1960s, two ecologists named Robert H. MacArthur and E. O. Wilson began this work. They wanted to predict how many species would live on a new island. They even tested their ideas in the Florida Keys.

They looked at small mangrove islands to see how life returned. They used a gas called methyl bromide to clear out the insects first. They found that islands closer to the mainland recovered much faster. This helped prove that their theory about distance was correct.

There are many specific facts that change how an island works. The size of the island and how far it is from others are key. The climate, like if it is hot or cold, also matters. Even the ocean currents can move seeds and birds to an island. Some islands have a rescue effect. This happens when new visitors arrive to help a group stay alive. Scientists also look at the species-area relationship. This shows that as an area gets bigger, the number of species usually grows too.

We can use these ideas to help protect nature today. Many national parks act like islands in a world of human buildings.

This is called habitat fragmentation. If a park is too small, it might lose its animals. This led to a big debate called SLOSS. This stands for "single large or several small." Some experts, like Jared Diamond, believe one large reserve is better than many small ones. We study these patterns to keep our planet's living things safe.

Insular biogeography is a specialized branch of biogeography. It examines the factors that influence species richness and diversification in isolated natural communities. While the name suggests oceanic islands, the field applies to any ecosystem surrounded by unsuitable habitat. This includes mountain peaks, seamounts, oases, and fragmented forests. It even applies to natural habitats isolated by human development, such as a patch of grassland surrounded by highways. In this field, an "island" is defined as any suitable habitat area surrounded by an expanse where that specific ecosystem cannot exist.

The core theory of insular biogeography proposes that the number of species in an undisturbed island is determined by two opposing forces: immigration and extinction. Immigration is the process of new species arriving at the island. Extinction is the process of species dying out within that environment. Over time, these two forces reach a balance known as an equilibrium level of species richness. This balance helps scientists predict how many different types of organisms will live in a specific isolated area.

Two main physical factors influence these forces: distance and size. The distance effect describes how isolation affects immigration. Islands located near a mainland or other islands receive more immigrants. Islands that are more isolated are less likely to receive new arrivals. This is because the distance makes it harder for organisms to travel. The species-area effect describes how island size affects extinction. Larger islands provide more habitat area and more diverse types of habitats, which is called habitat heterogeneity. This increased variety and space reduces the chance of species going extinct due to random events.

There are also specific modifications to these rules. The rescue effect occurs when populations on less isolated islands are saved from extinction by new immigrants. These newcomers bolster the existing population. Additionally, the target effect suggests that island size can influence immigration. Some species may actively target larger islands because they offer more resources and available niches. Larger islands might also accumulate more species simply by chance because of their size.

The field was established in the 1960s by ecologists Robert H. MacArthur and E. O. Wilson. They aimed to predict the number of species on newly created islands. They tested their theories in the Florida Keys using mangrove islands. Wilson and his student Daniel Simberloff used methyl bromide to clear arthropod communities from small islands. They monitored how quickly species returned. They found that islands closer to the mainland recovered faster, supporting the distance effect. This research helped prove that immigration and extinction patterns follow predictable rules.

Scientists also use the species-area relationship to understand these patterns. This concept shows that species richness is directly proportional to the area being studied. As the area of an island or ecosystem increases, the number of species typically increases as well. This relationship can be expressed mathematically through an equation where the number of species depends on the area. While this rule works well on oceanic islands, it also applies to Island Like Systems (ILS). An ILS is an ecosystem, like a pond, that is isolated within a different landscape. In these systems, the "mainland" is the source of new species, and the surrounding area is the "matrix."

These principles are vital for conservation biology. When humans build roads or housing, they cause habitat fragmentation. This turns national parks and reserves into islands. Scientists worry about "ecosystem decay," where these small islands lose species as they reach a new, lower equilibrium. This led to a famous debate called SLOSS, which means "single large or several small." Some ecologists, including Jared Diamond, argue that one large reserve is better than several small ones. This is because larger areas can hold more species and provide more stable environments for wildlife.