biogeog1.pdf

8/17/2019 biogeog1.pdf

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BIOGEOGRAPHY: DOES

THEORY MEETPRACTICE?


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Are we experiencing biodiversity crisis?


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Mass Extinctions

Ordovician

Devonian

Permian

Triassic

Cretaceous

Quaternary


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The 7th Mass Extinction

Holocene (present)

Anthropogenic cause

Depletion of natural resources

“The human population is

approaching the limit at which

an acceptable quality of lifefor its entirety can be

attained”

Wilson 1999


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Outline

An Insular Science

Patterns and Priority

Theory Into Practice: Problems and Prospects


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An Insular Science

Islands

Parcels of land surrounded by ocean

Facilitates several unusual evolutionary trends

Increased insularity and isolation is a major factorin accelerating species decline

Primary productivity by humans results in anincreasingly fragmented and compartmentalized

earth in which insularization of communitiesbecomes the norm leading to higher risk ofextinction

Persian carpet analogy (Quammen 1999)


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Conservation

Hotspots: islands of exceptional species richnessand endemism 25 documented global hotspots

44% of all species of vascular plants

35% of all species of four vertebrate groups

Confined to 1.4% of the terrestrial land surface of the earth

3 Key Strategies (Fonseca 2000)

Improved quantity and quality of data Enhanced collaboration with scientists

Closer co-operation with decision makers


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Reserve Selection

Bibby (1998)

Including a species at least once

≥95% chance of including a community at least once Representing each land system at least once

Wessels et al. (1999)

Land facets (simple units of a landscape with uniform

slope, soils, and hydrology)

Heterogeneity and biological richness are not always

correlated.


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Reserve Selection

Shafer (1999)

Complex criterion of ‘scenery’ may have been a

significant part of the decision-making process

Species-based approaches are themselves sometimes

flawed because they may fail to account the

multidimensional nature of biodiversity.


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Reserve Selection Maddock and du Plessis (1999) Use ecological or biogeographical zones

Turpie et. al. (2000)

Rarity algorithm – focused on the rare and endemic Greedy algorithm – focused on the total number of species

Ideal Reserve Network Optimum distribution of frequency of areas needed to

maintain one at least one population of each species

Selection of each new site is dependent on the previouslyselected site

Irreplaceability – occurrence of narrow endemics or aparticular combination of species is regarded irreplaceable


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Theory Into Practice: Problems and

Prospects

Equilibrium Theory of Island Biogeography

(MacArthur and Wilson 1967)

Species richness on an island

represents a dynamicequilibrium controlled by the

rate of immigration of new

species and the extinction of

previously established

species.

www.colorado.edu

Most of island biotas are

not in equilibrium due to

human impacts.


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Theory Into Practice: Problems and

Prospects

Mark V. Lomolino, Ph.D.

Island community

structure is dynamic over

time but not necessarily

represented by a balancebetween immigration and

extinction.

The hierarchical model

incorporates feedback

processes such as interspecificinteraction and offers

explanations for such insular

phenomena as the distribution of

individual species, species-area-

isolation relationships, and even

patterns of assembly.

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