Download Niche: lifestyle of a species includes: habitat, food, foraging route

Geog 316 Fall 2006
SFSU
Dr. B. Holzman
Patterns of Distribution
I. Species Niche
Ecological Tolerance
Eurytopic vs Stenotopic
II. Distribution Patterns
Continuous/Cosmopolitan
Disjunct Distributions
Evolutionary Relicts
Climatic Relicts
III. Endemism
Neoendemics
Paleoendemics
IV. Dispersal
Overcoming Dispersal Barriers
Corridors/Filters/Sweepstakes
Disharmonic distribution
Niche: lifestyle of a species
includes: habitat, food, foraging route,
season of activity, interaction with
other species
Distribution: where organisms are and
why includes range and extent of
influence
Scale: world, habitat, microhabitat
• Eurytopic: ecologically tolerant/ highly
efficient dispersal mechanisms
ex. plantain
Vespertionidae (bat family)
• Stenotopic: very specific preferences
and limited ecological tolerance
ex. damsel fly
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Geog 316 Fall 2006
SFSU
Dr. B. Holzman
• Barriers: restrictions, limitations
because of conditions: lack of food,
water, shelter.. physical resources that
will limit survival; can be "limiting
factors")
other barriers: rainfall, light intensity,
frost
Tropical Distribution of the palm family, Arecaceae.
Primary limiting factor is low temperature, few can
tolerate freezing, none can withstand extreme cold.
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Geog 316 Fall 2006
SFSU
Dr. B. Holzman
Sugar maple
Distribution Patterns
Continuous Distribution : area occupied by
groups consists of a single region or a number
of regions adjacent to one another
(usually explained by climatic or biotic
factors)
ex. shrew
Discontinuous Distribution: area occupied by
group is not continuous
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Geog 316 Fall 2006
SFSU
Dr. B. Holzman
Continuous Distribution
The species, Bradypus variegatus, is
endemic to the tropical and
subtropical regions of the American
continent (Grasse 1955).
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Geog 316 Fall 2006
SFSU
Dr. B. Holzman
At one time the black-footed
ferrets range extended from
southern Canada through the
12 Great Plains States:
Montana, Wyoming, eastern
Utah, Colorado, Arizona,
Texas, Oklahoma, Nebraska,
Kansas, New Mexico, North
Dakota, and South Dakota,
and on into northern Mexico
(Anderson 1972),
Cosmopolitan Distribution: distribution of
organisms found on all continents; broad
habitat preferences
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Geog 316 Fall 2006
SFSU
Dr. B. Holzman
Distribution: Cosmopolitan
Distribution: Cosmopolitan
Northern
hawk owl
Circumboreal distribution: around
the northern regions. distribution of organisms
possibly representing the past movements of
continents
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Geog 316 Fall 2006
SFSU
Dr. B. Holzman
Other continuous distributions
Distributions can also be
defined by location
i.e. Central West African
Distribution
• Disharmonic Distribution: a biota based
on those groups with good dispersal
capabilities
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Geog 316 Fall 2006
SFSU
Dr. B. Holzman
Discontinuous Distribution: area occupied
by group is not continuous
Disjunct Distribution: discontinuous
pattern -- areas occupied are widely
separated or scattered over a particular
continent or the world.
Such a pattern may represent....
Evolutionary or Climatic Relicts
Disjunct Distribution
Evolutionary relicts: once dominant and
widespread, but not able to compete
with newer life forms.
ex. Magnolias
Tulip trees
Distributions: Disjunct
Process: Evolutionary Relict
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Geog 316 Fall 2006
SFSU
Dr. B. Holzman
Disjunct Distributions:
Process: Evolutionary Relict
Disjunct :Relicts
Climatic relicts or Habitat relicts:
affected by past changes in climate,
glaciations or sea level or geologic
separation due to plate tectonics
ex. gorilla , carabidae
Climate relict
• Dodecatheon: glacial relict
Dawn redwood: Pre glaciation
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Geog 316 Fall 2006
Disjunct Distribution
SFSU
Dr. B. Holzman
Mountain gorilla
Lowland gorilla
Continental Drift
• Plate Tectonics and
Continental Drift:
evidence for drift -- the
distributions, past and
present, of organisms
– Drifting of continents
from 250mya to
present: Pangaea,
Gondwanaland, Laurasia
– the importance of
drift: enhances
speciation, changes
climate
DISJUNCT DISTRIBUTION
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Geog 316 Fall 2006
SFSU
Dr. B. Holzman
DISJUNCT DISTRIBUTION
Endemic Organisms
ENDEMIC: a taxon native to a particular
place and restricted to that geographic
area specified, such as a lake, continent,
biome or island (organisms confined to the
areas where they evolved)
Two major reasons /factors influencing
the degree of endemism in an area
1) isolation
2) stability
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Geog 316 Fall 2006
SFSU
Dr. B. Holzman
Kangaroo rat
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Geog 316 Fall 2006
SFSU
Dr. B. Holzman
Neoendemics: may be endemic only
due to restricted time to expand
range
Paleoendemics: ancient endemics, old
species that have been restricted
Neoendemics
•
Neoendemics are found frequently in geologically youthful habitats, and
often their rarity is partly a function of their youth - in some cases
these plants have not had time to expand their range from their point
of origin to their climatic and geological limits.
Limnanthes floccosa
Oenothera californica
Paleoendemics
• Carpenteria californica, Lyonothamnus floribundus, Pinus radiata,
P. torreyana, and Sequoiadendron gigantea are paleoendemics
that were once more broadly distributed, but have retreated to
their current ranges in response to dramatic climatic change.
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Geog 316 Fall 2006
SFSU
Dr. B. Holzman
Dispersal
• Dispersal:
movement of individuals from a
location within their species’ geographical
range to an area outside of that range.
The Importance of Dispersal
• Dispersal is a biogeographic process that is
part of the life history of every species, it is
an important part of the process of evolution.
• Dispersal is effected by ecological factors
which limit distribution of plants and animals –
climate, substrate, biotic factors, and
historical factors.
• Without dispersal, genetic interchange is
limited
Dispersal Basics
• To disperse is “to scatter or
distribute in various
direction”
• Diffusion is the gradual
movement of populations
across suitable terrain that
promotes a uniform density
of individuals in the region
• Jump dispersal is the
movement of individuals
across great distances
followed by successful
establishment
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Geog 316 Fall 2006
SFSU
Dr. B. Holzman
Dispersal Basics
• Long-distance, jump, or waif
dispersal
– Dispersal across a
biogeographical barrier
– Example: Bird flying to an
oceanic island
– Explains disjunct
distributions and
colonization patterns on
oceanic islands
• Diffusion
– Movement of a population
across a geographical
area
– Example: Pine trees
moving north after glacial
retreat
Modes of dispersal
• Passive vs. Active
Wind, raft, birds, larval
dispersal, migrating
islands, agriculture or
anthropogenic
Animals: walking,
swimming, flying
Plants: eaten by animals,
wind blown, agriculture
Dispersal
• Anemochores:
dispersed by wind
• Hydrochores:
dispersal by water
– Anemohydrochores
• Zoochores:
dispersed by animals
• Anthropochores:
dispersed by humans
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Geog 316 Fall 2006
SFSU
Dr. B. Holzman
Plant dispersal
Physical Barriers can be climatic, topographic
or a combination
ex. water: barrier to terrestrial animals
land : barrier to marine organisms
mtn. ranges:
Dispersal Routes
Corridors:
Filters:
Sweepstakes:
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Geog 316 Fall 2006
SFSU
Dr. B. Holzman
Dispersal Routes
Corridors: pathways or easiest route,
includes a wide variety of habitats, very
little trouble traversing the corridors,
two ends are almost identical in their
biota
Filters: more limited variety of habitats,
allows only certain animals to get
through
European starling
Corridor
Corridor
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Geog 316 Fall 2006
SFSU
Dr. B. Holzman
Filter
Filter
Sweepstakes: occasional arrivals: areas
isolated and organisms get across by
luck, attached to log/plant material,
wind blown, etc.
Disharmonic distribution: biota only
contains species with good dispersal
mechanisms and has no species with
poor dispersal capabilities
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Geog 316 Fall 2006
SFSU
Dr. B. Holzman
Disharmonic distribution
Conclusion
• Organisms separated by great physical barriers are
can be quite different, despite having similar physical
environments
• Distribution patterns lead many to infer about
dispersal process
• There are limitations of dispersal as an explanatory
vehicle: species-area relationships, spatial affinity
• A comprehensive approach to dispersal of taxa needs
to be inclusive of geologic hypothesis, existing and
past distributions, relationship among species to
areas and evolutionary information
Patterns of Distribution
I. Species Niche
Ecological Tolerance: Eurytopic vs Stenotopic
II. Distribution Patterns
Continuous/Disjunct Distributions
Cosmopolitan
Circumboreal
Evolutionary Relicts/ Climatic Relicts
Disharmonic distribution (islands)
III. Endemism
Neoendemics (newer distribution)
Paleoendemics (ancient species)
IV. Dispersal
Dispersal methods
Overcoming Dispersal Barriers
Corridors/Filters/Sweepstakes
Disharmonic distribution (islands)
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