Transcript ppt

CONSERVATON BIOLOGY
Lecture05 – Spring 2016 Althoff - reference Chapters 6-10
THREATS TO BIODIVERSITY
Part II
Extinction Process
• Why are some species more vulnerable to
extinction than others?
SIMPLE ANSWER– ________________
• Examples from Hunter and Gibbs:
a) bighorn sheep occupying semi-isolated
ranges
b) bird species on islands off the coast
of Great Britain
Extinction Process
BIGHORN SHEEP POPN ON SEMI-ISOLATED
MOUNTAIN RANGES
Extinction Process
BIRD SPECIES (62 SPECIES) ON ISLAND OFF
THE COAST OF BRITIAN
Fail:
Persists
Why are some species rarer than others?
1• Restriction to an _____________ type of habitat
2• Limitation to a ________ geographic range
3• Occurrence only at ______ population densities
1 Restriction to an uncommon type of habitat
• May have resulted because they evolved
___________ characteristics that allow them to
live there and nowhere else.
Ex. Naked mole rats; black-footed
ferrets
Cave-dwelling invertebrates,
fishes,
and amphibians
• Some may been successful there simply
because they ________ successful any place
else (i.e., cannot out compete other species).
Ex. Steamboat buckwheat
2
Limitation to a small geographic range
• May have resulted from geographic _______
Ex. Populations on Islands, in a lake
(cichlid fishes in Lake Malawi Africa)
• ______ range of “tolerable” conditions can
result in small geographic range
Ex. Many Amazonian plant species
evolved in special soil conditions.
Ex. Plant species in bogs where very
acidic conditions
3 Occurrence only at low population densities
• Body size: large animals take lots of space
Ex. Elephants, moose, elk (in certain
settings)
• Small density populations persist because they do
well when they __________ with one another.
Ex. Wolverines, Hawaiian hawk
Usually, a species exhibits just ____ of the 3
basic “rare” charactistics, but…
• A few species may have 2 or even 3 of the “rare”
characterisitics
1• Rare habitat
2• Small geographic
range
3• Low popn density
Why are Rare Species Usually More
Vulnerable to Extinction than Common Species?
• #1 likely reason: rare species have a greater chance
of being pushed into extinction because of
_____________________—especially if they have a
small geographic range….about ¾ of all known
extinctions since 1600 have been island species
• Other reasons could include: _______________
______ (especially if biased against females),
______________ problems (genetic drift,
inbreeding, and bottlenecks)
Why are Some Species Particularly Sensitive to
Human-induced (anthropogenic) Threats?
1• __________________________________ : low
reproductive rate (small number of progeny, long
generation time, etc.), limited dispersal capabilities,
inflexible habitat requirements, etc.
2• ______________: singled out by people. Examples
include wolves and African wild dogs (to eliminate
threat of livestock loss), passenger pigeons (edible),
diamond-backed turtles (edible)
Why are Some Species Particularly Sensitive to
Human-induced (anthropogenic) Threats?
…con’t
3• ____________________: those tied to ecosystems
preferred by humans are more at risk—think areas
with fertile soils (prairies vs. agriculture) or abundant
water resources (for hydroelectric power, etc.)
4• ________________________: Fragmentation can
reduce extensive tracts of one habitat-type or
another (think many large terrestrial carnivores/
predators).
Patchy Distributions and Metapopulations
• ______________ = model of population structures
whereby each patch of habitat contains a different
subpopulation of a species. A group of “patch”
populations is collectively a metapopulation.
Metapopulation __
Metapopulation __
Examples of Metapopulations
•
•
•
•
•
Prairie chickens
Sage grouse
Black-footed ferrets
Piping plovers
Green salamanders
Keep in mind….
• ______ species that are distributed in habitat
patches are composed of metapopulations.
Often bird species—being highly mobile—
are not as likely to exhibit metapopulation
structure
• Metapopulations is a concept associated
with _________________________
____________________
• Metapopulation dynamics can be viewed as
two types of subpopulations & two types of
processes……
Subpopulations & Processes Associated
with Metapopulation Dynamics
• Two subpopulation types:
1) ________ popn
2) ________ popn
• Two processes:
1) local ______________
2) ______________ (recolonization)
Source vs. Sink (sub)populations
• Source: produce substantial number of
_________ that ___________________
• Sink: do ____ produce enough individuals to
maintain their local numbers and typically
only continue to exist through _______
__________ from other subpopulations (aka
source subpopulations.
Sink (sub) populations….
• Are inherently _____ to go ______ (aka local
extinctions) because the habitat they occupy
is either too small or of too poor quality to
regularly (for years and years and years)
produce enough offspring to remain
sustainable
• And, often can be colonized (or recolonized)
by dispersing individuals from source
populations because they appear to be
suitable habitat for breeding/reproducing
Sink (sub) populations….examples
• Cache River prothonotary warbler subpopulation
(Wing & Prayer video)
• Dickcissel population in Central Prairie
Sutton Center
Oklahoma
Cowbird brood parasitism of Dickcissels
In summary…
• The metapopulation concept offers a framework for
understanding the dynamics of populations in
_________ landscapes (i.e., think fragmentation)
• Subpopulations are subject to (local) extinction and
colonizations (recolonizations)….as influenced by
____________ subpopulations within the
metapopulation
• Patchy landscapes (aka fragmentation) is
becoming more and more common because of
_________ activity.
• However, do not assume ALL at-risk species
conform to the metapopulation concept
In summary…con’t
• Some species are rare than others because they
are 1) restricted to an uncommon habitat type, 2)
are limited in their geographic range, and/or 3)
occur only a low population densities.
• In rare instances, a species might have all 3 of the
above characteristics.
• Many species are at-risk due to anthropogenic
influences:
1) limited adaptability & resilence
2) human attention
3) ecological overlap
4) large home-range requirements