Biogeography of Islands

Oceanic islandsSky islands (mountain tops)Forest fragmentsPrairie potholesPrairie remnants

Biogeography of Islands

Oceanic islandsSky islands (mountain tops)Forest fragmentsPrairie potholesPrairie remnants

Today, we are going to test a theory of Island Biogeography in the Jordan River “nurse logs” – or “islands”

Biogeography of Islands

Islands biologically important

1. Dispersal biology

Nature of island biota: how it differs from that of the source-area, and the nature of adaptations of the successful immigrants that permitted them to reach and colonize the island

Biogeography of Islands

Islands biologically important

2. Island Biogeography

Identifying and quantifying the factors that control 3 phenonmena:

rate of island immigration

rate of island extinction

number of species per island

Biogeography of Islands

Islands biologically important

3. Adaptive radiations

Processes of change by which immigrant species diversify and radiate to occupy ecological niches that on the mainland are normally occupied by other groups

Biogeography of Islands

Hawaiian Lobeliads

• Early lobeliads had initial radiation with Hawaiian honeyeaters

• later radiation of two large genera (Cyanea and Clermontia) pimarily with Hawaiian honeycreepers

Hawaiian Lobeliads

Island Biogeography

Island patterns: three interrelated ecological and biogeographical observations of patterns on islands have been made

Island Biogeography

1. Species-area relationships

Relationship within archipelagos between the sizes of individual islands and the number of species that comprise their biota.

Island Biogeography

1. Species-area relationships

Relationship within archipelagos between the sizes of individual islands and the number of species that comprise their biota.

Long been recognized that larger islands have more species

Philip Darlington quantified this relationship for the herptofauna of the West Indies

Island Biogeography

1. Species-area relationships

Relationship within archipelagos between the sizes of individual islands and the number of species that comprise their biota.

In order to double the number of species, the size of the island had to increase 10 fold

Island Biogeography

This general relationship (although with different ratios) was later seen with flowering plants and birds in the Pacific.

Island Biogeography

This general relationship (although with different ratios) was later seen with flowering plants and birds in the Pacific.

Island Biogeography

2. Effect of isolation

Isolated islands have fewer species than expected based on size alone.

Island Biogeography

3. Species turn-over

Islands have more species turnover than continental landmasses.

Island Biogeography

3. Species turn-over

Islands have more species turnover than continental landmasses.

Island Biogeography

3. Species turn-over

Islands have more species turnover than continental landmasses.

• number of bird species increased rapidly until 1920, and then species number remained relatively constantdespite changes in composition of the avifauna

• some of the later arrivals were successful colonists, replacing about an equal number of species that became extinct

Island Biogeography

Robert MacArthur (ecologist, competetion) and E.O. Wilson (ant taxonomist, biogeographer) produced in 1963 (small paper in Evolution) and 1967 (book at right) a unifying theory to explain these three basic characteristics of insular biotas:

Island Biogeography

1. Number of species increases with increasing island size

2. Number of species decreases with increasing distance to the nearest continent or other source of species

3. Continual turnover in species composition due to recurrent colonizations and extinctions, but the number of species remains constant

Island Biogeography

Island Biogeography

Ivory-billed woodpecker-considered extinct since 1944

Island nature of its habitat today — swamp forest in Arkansas where re-discovered in 2004

Applications of Island Biogeographic Theory to Nature PreservesSLOSS Single Large or Several Small

Island Biogeography

Applications of Island Biogeographic Theory to Nature PreservesSLOSS Single Large or Several Small

Island Biogeography

Single Large vs. Several Small

Circular vs. "Peninsular”

Clumped vs. Spread out

Connected vs. Unconnected

Island Biogeography

Today, we are going to test “species-area”relationships in the Jordan River “nurse logs”

Island Biogeography

Today, we are going to test “species-area”relationships in the Jordan River “nurse logs”

1. Measure area of “nurse log” islands and record numbers of vascular species

2. We will graph out species-area relationships (including previous years’ data) – you may see these results on the final

3. Group 1: Wes, Anne, Liz, Melissa, Joey, Wynston4. Group 2: Emily, Ashley, Giacomo, Joshua, Dillon

Method