WFB074 Lecture 16: Island Conservation & Extinctionsjdecher/WFB074_2012/Lec16_IslandEcosystem...WFB074 Announcements Midterm results Count (N) 72 Minimum Value 28 Maximum Value 53

WFB 074 Lecture 16: Island Conservation & Extinctions

Readings this Week (Part 1)

Powledge, F. 2003. Island biogeography’s lasting impact. BioScience 53:1032–1038. Wilcove, D. S. 1999. The Condor’s Shadow: the Loss and Recovery of Wildlife in America. pp. 203-241, Chapter 7: Too gentle for this world. New York: W. H. Freeman & Co. Finlayson, C., and T. Finlayson. Undated Brochure. Invasive plant threatens Midway Atoll seabirds. US Fish and Wildlife Service, Midway Atoll National Wildlife Refuge.

WFB 074 Announcements

Midterm results

Count (N) 72

Minimum Value 28

Maximum Value 53

Average 42.25

Median 42.5 Standard Deviation 6.09

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25

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35

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>50 pts 41-50 pts

31-40 pts

21-30 pts

11-20 pts

1-10 pts

WFB 074 – Lecture 16: Island Conservation & Extinctions

Types of Islands

Part of continental shelf.

Once -or periodically, through earth history -

connected to mainland.

Sri Lanka, Sumatra Map from:

http://www.emsc-csem.org/

Continental or Landbridge Islands

Types of Islands Oceanic Islands Arise from beneath the ocean surface, volcanic

San Benedicto Island of the

west coast of Mexico:

1952 eruption doubled size of

island.

Photo: Luke Wooller, Picasa


How do plants and animals get to islands?

Chance Dispersal

Juvenile sooty tern with fruits of the Boerhaavia diffusa attached near its eye.

Fruits of Boerhaavia diffusa reveal sticky yellowish ribs, in addition to sticky hairs. Ideal for catching onto feathers…

Heimerliodendron brunonianum has fruits with ridges that are amazingly sticky. Unlike rubber cement, this substance takes years to dry.

Map: Carlquist 1981 Photos: http://www.sherwincarlquist.com/dispersal-to-islands.html


How do plants and animals get to islands?

Island Rafting

from: Carlquist. 1965. Island Life


Characteristics of Islands

The number of species increases with Island

Area

Relationship between Number of Species (S) and Island Area (A) for the reptiles and amphibians of the West Indies (Data from Darlington 1957). Note: Axes are logarithmic. This can be expressed with equation:

S = c Az

Where c and z are fitted values (constants). = Species-Area Relationship



On islands, the number of species decreases

with isolation

Effect of distance from mainland… bird species in the Lesser Antilles

(David Lack)



The near island curve indicates a higher rate of species colonization because it will simply be easier for animals to migrate out to a near island. The far island rate is lower because the farther from the source area an island is, the more difficult it will be for species to reach it.

Island Colonization


At first (left side of the graph) the colonization rate will be high because there are lots of open ecological niches on the island that can be easily filled. Rapid dispersers on the mainland (source area) will find the island quickly.

The two curves represent Near Islands and Far Islands relative to the source area.

“empty” island

“full” island


Extinction Curves

A large island will hold more species, it will have relatively low rates of extinction compared to a small island. A small island will theoretically suffer higher rates of extinction due to lesser area and resources for species.


Characteristics of Islands Combining Colonization Rate and

Extinction Rate

= Mac Arthur and Wilson’s Equilibrium Model of Island Biogeography (1963).

The number of species increases with area and decreases with isolation of an

island

Predicted equilibrium points for four separate case: SFS = Species # for a far, small island; SNS = species number for a near, small island SFL = Species number for a far, large island SNL = Species number for a near, large island.



= Mac Arthur and Wilson’s Equilibrium Model of Island Biogeography (1963).

The number of species increases with area and decreases with isolation of an

island


E.O. Wilson Robert H. MacArthur

WFB 074 -‐ Island Ecosystems & Extinctions

Unique Island Faunas

Live in crevices and burrows along lava coast. Only lizard at home in the surf. Feeds off brown slimy fonds of Sargassum, a brown alga. Unafraid of humans.

Unusual Island Adaptations

Galapagos

Marine Iguanas Amblyrhynchus

cristatus


Unique Island Faunas Gigantism Galapagos tortoises Chelonoidis (Geochelone) nigra Distinctive races throughout the islands.


Chelonoidis nigra ssp. abingdoni IUCN Red List: EW (Extinct in Wild)


Unique Island Faunas Gigantism & Flightlessness in Birds


Elephant Bird (Aepyornis) of Madagascar extinct ~ 1650

Mauritius Dodo (Raphus cucullatus) Related to Pigeons and Doves (Columbidae). Short description by Dutch admiral Cornelis Matelief de Jonge in 1606. Extinct about 1665.


Unique Island Faunas Gigantism & Flightlessness in Birds


Kakapo (Strigops habroptila) Flightless nocturnal parrot endemic to New Zealand. World’s heaviest parrot.

One of the last kakapos on Maud Island in New Zealand's Marlborough Sounds is fed by conservation officer Daryl Eason in 1998. (http://www.smh.com.au)



Galapagos

Galapagos Finches

“The remaining land-birds form a most singular group of finches…All are peculiar to this archipelago… Seeing this gradation and diversity of structure in one small, intimately related group of birds, one might fancy that from an original paucity of birds in this archipelago, one species had been taken and modified for different ends.” (Charles Darwin, Voyage of the Beagle)

WFB 074 – Lec. 16 -‐ Island Conservation Hawaiian Archipelago


Unique Island Faunas Hawaii



Hawaii

Hawaiian Honeycreepers (Drepanididae)

Originally about 33 species. At least 10 sp. extinct. Most remaining species are endangered.


Adaptive Radiation of Hawaiian Honeycreepers

(Drepanididae)

Hawaii


From Brown & Lomolino 1998


Example: Palila

(Loxioides bailleui) on mamane tree

Hawaii Honeycreepers


Finch-like bill. Specialized ecological niche on upper slopes of Mauna Kea. Dry open mamane woodlands. Described as numerous in 1892. Habitat loss from introduced livestock. Less than 10% off former range remains.


Example: Akiapolaau

(Hemignathus munroi)


WFB 074 - Island Ecosystems & Extinctions

Curved beak. Upper beak longer than lower beak. Bark Pickers. Insectivorous.


Example: Akohekoe

Crested Honeycreeper

(Palmeria dolei)

WFB 074 - Island Ecosystems & Extinctions

Survives only in narrow belt of rainforest on the upper slopes of Haleakala volcano on Maui. First known nest discovered only recently.


WFB 074 -‐ Island Ecosystems & Extinctions Introduced Species

GOAT MONGOOSE PIG


New Zealand’s Stephen Island

Stephen Island Wren (Xenicus lyalli)

Ornithologist W. R. B. Oliver: “The history of this species, so far as human contact is concerned, begins and ends with the exploits of a domestic cat. In 1894 the lighthouse keeper’s cat brought in 11 specimens, which came into the hands of H. H. Travers… A few more captures made and duly reported by the cat and then no more birds were brought in. It is evident, therefore, that the cat which discovered the species also immediately exterminated it.”

(from S. Carlquist. 1965. Island Life)


Managing Feral Pigs on Hawaii

More on this at Cornell Lab of Ornithology: http://www.birds.cornell.edu/AllAboutBirds/conservation /success/hawaiian_honeycreepers

Nonnative feral pigs degrade native wet forests in Hawaii via rooting and mixing of soil horizons, trampling and consumption of native plants, and transport of nonnative seeds (Photo: Hawaii Volcanoes National Park). See Dr. Creighton Litton website: Dept. of Nat. Resources & Env. Management (Univ. of Hawaii, Manoa): http://www.ctahr.hawaii.edu/littonc/research.html


In-class VIDEO: Scene 10 “Under Threat from a Plant” from Nat. Geogr. “Hidden Hawaii” Managing Golden Crownbeard (Verbesina encelioides) on the Hawaiian Islands

Documents

WFB074 Lecture 16: Island Conservation & Extinctionsjdecher/WFB074_2012/Lec16_IslandEcosystem...WFB074 Announcements Midterm results Count (N) 72 Minimum Value 28 Maximum Value 53