Transcript distribution

Ecology
Chapter 09
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Outline
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Distribution Limits
Distribution Patterns
Organism Size and Population Density
Commonness and Rarity
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Introduction
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Ecologists usually define a population as a
group of individuals of a single species
inhabiting a specific area. (族群)
 Characterized by the number of
individuals and their density.
 Additional characteristics of a population
include age distributions, growth rates,
distribution, and abundance.
(分佈)
(數量)
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Distribution Limits (分佈限制)
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Physical environment limits geographic
distribution of a species.
 Organisms can only compensate so much
for environmental variation.
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Kangaroo Distributions and Climate
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Caughley found a close relationship between
climate and distribution of the three largest
kangaroos in Australia.
 Macropus giganteus - Eastern Grey
 Eastern 1/3 of continent.
 Macropus fuliginosus - Western Grey
 Southern and western regions.
 Macropus rufus - Red
 Arid / semiarid interior.
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Kangaroo Distributions and Climate
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Kangaroo Distributions and Climate
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Limited distributions may not be directly
determined by climate.
 Climate often influences species
distributions via:
 Food production
 Water supply
 Habitat
 Incidence of parasites, pathogens and
competitors.
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Tiger Beetle of Cold Climates
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Tiger Beetle (Cicindela longilabris) (長唇虎甲
蟲) lives at higher latitudes and elevations
than most other species in NA.
 Schultz et. al. found metabolic rates of C.
longilabris are higher and preferred
temperatures lower than most other
species.
 Supports generalization (概說) that the
physical environment limits species
distributions.
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Tiger Beetle of Cold Climates
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Figure 09_04
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Ecologists suggest that during the last glacial
period C. longilabris lived far south of its present
range limits. Then with climatic warming and the
retreat of the glaciers, the tiger beetles followed
their preferred climate northward and up in
elevation into the mountains of western North
America.
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Distributions of Plants along a MoistureTemperature Gradient
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Encelia species distributions correspond to
variations in temperature and precipitation.
pubesent
扁果菊
加州扁果菊
縟扁果菊
銀色扁果菊
nonpubesent
木扁果菊
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有軟毛的
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pubesent
nonpubesent
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Distributions of Barnacles along an
Intertidal Exposure Gradient
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Organisms living in an intertidal zone have
evolved to different degrees of resistance to
drying.
 Barnacles show distinctive patterns of
zonation within intertidal zone.
 Connell found Chthamalus stellatus (小
藤壺) restricted to upper levels while
Balanus balanoides (巨藤壺) is limited
to middle and lower levels.
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Distributions of Barnacles along an
Intertidal Gradient
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Balanus appears to be more vulnerable to
desiccation, excluding it from the upper
intertidal zone.
 Chthamalus adults appear to be excluded
from lower areas by competition with
Balanus.
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Distributions of Barnacles along an
Intertidal Gradient
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Distribution of Individuals on Small Scales
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Random: Equal chance of being anywhere.
 Uniform distribution of resources. (隨機)
Regular: Uniformly spaced. (均勻)
 Exclusive use of areas.
 Individuals avoid one another.
Clumped: Unequal chance of being anywhere.
 Mutual (相互的) attraction between
individuals.
 Patchy (不勻稱) resource distribution. (叢集)
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Distribution of Individuals on Small Scales
敵對的
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Distribution of Tropical Bee Colonies
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Hubbell and Johnson predicted aggressive
bee colonies would show regular distributions
while non-aggressive species would show
random or clumped distributions.
 As predicted, four species with regular
distributions were highly aggressive.
 Fifth was non-aggressive and randomly
distributed.
 Prospective nest sites marked with
pheromones. (費洛蒙)
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有背無刺蜂
黃腹無刺蜂
競爭者
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Distributions of Desert Shrubs
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Traditional theory suggests desert shrubs
are regularly spaced due to competition.
 Phillips and MacMahon found distribution
of desert shrubs changes from clumped to
regular patterns as they grow.
 Young shrubs clumped for (3) reasons:
 Seeds germinate at safe sites
 Seeds not dispersed from parent areas
 Asexual reproduction
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Distributions of Desert Shrubs
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Phillips and MacMahon proposed as plants
grow, some individuals in clumps die,
reducing clumping.
 Competition among remaining plants
produces higher mortality.
 Eventually creates regular distributions.
Brisson and Reynolds found competitive
interactions with neighboring shrubs appear
to influence distribution of creosote roots,
Larrea tridentata.
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Creosote bush
三齒拉瑞阿
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Heterogeneity in
Rangelands
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• The root systems of creosote bushes overlap much less
than they would if they had circular distributions.
• Brisson and Reynolds conclude that creosote bushes
compete for belowground resources.
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Distributions of Individuals on Large Scales
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Bird Populations Across North America
 Root found at continental scale, bird
populations showed clumped distributions
in Christmas Bird Counts.
 Clumped patterns occur in species with
widespread distributions.
 Brown found a relatively small proportion
of study sites yielded most of records for
each bird species in Breeding Bird Survey
(繁殖鳥類調查).
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短嘴鴨
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魚鴨
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人口普查
綠鵑
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Plant Abundance along Moisture Gradients
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Whittaker examined distributions of woody
plants along moisture gradients in several
North American mountain ranges.
 Documented moisture gradient from moist
canyon bottoms up to the dry southwestfacing slopes.
 Tree species showed a highly clumped
distribution along moisture gradients,
with densities decreasing substantially
toward the edges of their distribution.
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Organism Size and Population Density
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In other words, like birds, tree populations are
concentrated in hot spots.
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石松
亞歷桑那野草苺
西部黃杉
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針刺松
紅槭
加拿大鐵杉
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Organism Size and Population Density
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In general, population density declines with
increasing organism size.
 Damuth found the population density of
herbivorous mammals (草食性哺乳類)
decreased with increased body size.
 Peters and Wassenberg found aquatic
invertebrates tend to have higher
population densities than terrestrial
invertebrates of similar size.
 Mammals tend to have higher population
densities than birds of similar size.
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Organism Size and Population Density
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Plant Size and Population Density
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Plant population density decreases with
increasing plant size.
 Underlying details are very different.
 Tree seedlings can live at very high
densities, but as the trees grow, density
declines progressively until mature trees
are at low densities.
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紫萍
無性生殖多年生的
北美紅杉
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Duckweed
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Commonness and Rarity (普遍 & 稀有)
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Rabinowitz devised commonness
classification based on combinations of
three factors:
 Geographic Range of Species (extensive
versus restricted)
 Habitat Tolerance (broad versus small)－
is related to the range of conditions in
which a species can live
 Local Population Size (large versus
narrow)
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Commonness and Rarity (普遍 & 稀有)
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Some plant species can tolerate a broad
range of soil texture, pH, and organic matter
content, while other plant species are
confined to a single soil type.
Tiger have broad habitat tolerance.
Snow leopard is confines to a narrow range
of conditions in the high mountains of the
Tibetan Plateau.
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Commonness and Rarity (普遍 & 稀有)
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Small geographic range, narrow habitat
tolerance, and low population density are
attributes of rarity.
Populations that are least threatened by
extinction, have extensive geographic
ranges, broad habitat tolerances, and some
large local populations.
 All seven other combinations create some
kind of rarity.
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Rarity
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Rarity I
 Extensive Range, Broad Habitat
Tolerance, Small Local Populations
 Peregrine Falcon (遊隼)
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Peregrine Falcon
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Rarity
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Rarity II
 Extensive Range, Large Populations,
Narrow Habitat Tolerance
 Passenger Pigeon
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Passenger Pigeon
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Rarity
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Extreme Rarity III
 Restricted Range, Narrow Habitat
Tolerance, Small Populations
 California Condor (兀鷹)
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California Condor
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放射松
加拉巴哥中型地雀
弗里芒氏楊
線葉鐵角蕨
夏威夷菊
魚鴨
袋獾
千歲蘭
短葉紅豆杉
卜力查得棕樹
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Welwitschia
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Pritchardia monroi
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