Transcript PowerPoint Presentation - #2 Speciation and Biodiversity

Biodiversity and conservation
 Genetic diversity: within species
variation (e.g corn [Zea mays] in
North vs. Central America)
 Species diversity: species
richness
 Ecosystem diversity: variety of
habitats
Basic questions in
biodiversity research:
for any plot of land (or patch of sea)
• Why does it contain this many plant
and animal species, and not more, or
less?
• Why is species Y common and species
X rare?
The standard answer:
• “it depends on the # of available
niches”,
OR “it depends on….”:
• Availability of resources / intensity
of competition, predation, infection,
etc.
The ‘neutral’ answer*:
• It depends on chance!
• Diversity = f(immigration, extinction, evolution)
• Consider the example of a patch of
tropical forest in Panama - how many
tree species will it contain?
*Hubbell, S.P. 2001. The unified neutral theory of biodiversity and biogeography, Princeton U.P.
Tree diversity of a Panamanian forest
How many trees
can island sustain?
Immigration
rate?
How diverse is the
forest “reservoir”?
How fast are new
tree species evolving?
Satellite image of Barro Colorado Island, Panama (Image: NASA);
Map source: www.geographic.org, used with permission
Testing Hubbell’s model on Barro Colorado
Patterns of biodiversity
1. Latitudinal gradient in
species richness
diversity gradient
Global species richness
(composite index)
Hotspots
Biodiversity as a function of latitude
(North and Central America)
Birds
Labrador
Beetles
81
Labrador
Ants
169
Alaska
7
New York 195
Massachusetts 2000
Iowa
73
Guatemala 469
Florida 4000
Trinidad 134
North America
S. Florida
Diversity of
North
American
tree
species
Biodiversity gradients (tree species) in
temperate coastal evergreen forests
Biodiversity gradients in the temperate
coastal evergreen forest of North America
Ranges of
newts and
salamanders
in the
temperate
evergreen
forests of
western
North
America
Patterns of
biodiversity
2. Altitudinal gradient
Altitudinal
gradients
in bird
species
diversity
Birds
Species
richness and
temperature
range
Mammals
Snails
Biodiversity and moisture availability
Ants
Rodents
Species richness and productivity
N. American data
Habitat complexity
(e.g. # of forest strata)
Low complexity
(single stratum)
High complexity
(multi-strata)
approx. equivalent tree species richness
Species diversity and habitat complexity
Conservation of biodiversity
• Are we engaged in a “biotic holocaust”?
• How many species are currently being
lost?
• Why is biodiversity important?
• How can species conservation be best
achieved?
Conservation of biodiversity
Extinction - the demise (locally or
globally) of a species;
Endangered species - a species or
subspecies that is at risk of extinction
throughout all or part of its range;
Threatened (or vulnerable) species possibly at risk of extinction in the near
future
Species under threat:
endemics:
(e.g. Hawai’ian honeycreepers)
• Generally very small
populations
• At risk from habitat
loss and introduction
of aliens (particularly
predators)
Island endemics under threat
e.g. Canary Islands
• ~4 000 endemic or
native plant and animal
species live in the
archipelago (cf. ~100 in
British Isles).
Canary Islands endemics
• On average a new species invades every 17 days; a
new serious pest invades on average every 6
months.
• Most problematical pests are the Barbary ground
squirrel, the Corsican mouflon, and most recently,
a beetle (“picudo rojo”), that feeds on native
palms.
• 20 endemics are considered endangered; several
have <100 individuals left.
Source: New York Times, Aug. 29, 2006, p. A4
Species under threat:
widespread species and range
collapse
Population collapse is generally accompanied
by (or caused by) range collapse (e.g.
American bison; giant panda; black-footed
ferret).
In most cases marginal populations, which
may have distinctive genomes, are the only
survivors.
What is the current extinction rate?
Very difficult to demonstrate that a species
is truly extinct (e.g. the ivory-billed
woodpecker of the SE USA) so estimates of
modern extinction rates vary widely.
Colinvaux notes that the rate is “incalculable”;
Myers (1979) says “we have no way of knowing
… let alone an approximate guess”.
Biotic holocaust?
Extreme estimates of current annual
species loss:
40,000 (Myers, 1979)
widely cited in 1980-90’s (e.g. by Al Gore)
27,000 - 100,000* (Wilson, 1992)
*20% of all species gone by 2020!
250,000** (Ehrlich, cited in Stork,
1997)
**all species gone by 2010-2025!
Sources for previous estimates
• Myers, N. 1979. The Sinking Ark.
Pergamon Press.
• Wilson, E.O. 1992. The Diversity of
Life.
• Stork, N.E. in: Wilson, E.O. et al.,
1997. Biodiversity, pp. 41-68.
Alternative estimates
• A much lower estimate of ~1400
extinctions per yr (=0.7% in 50 years)
was derived by Lomborg (1998). This
is still ~1500 times greater than
estimated “background” rates from
geological data
Lomborg (1998) The Skeptical Environmentalist:
Measuring the Real State of the World. Cambridge
U.P.
Modern extinctions:
a fishy example
In the Nearctic realm 1033 species of fish are
known to have inhabited streams and lakes in
recent historic times. Of these, 27 (3%) are
thought to be extinct, and 277 (28%) are
endangered or vulnerable. The factors that
caused these declines are habitat destruction,
introduction of alien species, pollution,
hybridization and over-harvesting.
1830
1882
1902
1950
Forest
fragmentation:
Wisconsin
(1830-1950).
Area: 100 km2
shaded = forest
white = agriculture
(prairie in 1830)
Forest fragmentation:
Bahia (coastal S. Brazil)
dark = forest; light = agriculture
Habitat loss and extinction:
model predictions
Galapagos
How many species have gone extinct as a
result of diminished habitat area?
• 99% of primary forest of eastern US lost
from 1800-2000; only one bird species
extinct (Simberloff)
• 88% of forest along Atlantic coast of
Brazil cleared in same period; none of the
171 animals have gone extinct (Brazilian
Soc. Zoologists).
• See Lombock (1998) for discussion of
these and other examples
Slow relaxation to a new
equilibrium with changing island
area
Forest fragmentation:
Rondonia, Brazil
100 km2
1975
1992
Forest fragmentation
experiment, Amazonas
Thomas Lovejoy, Smithsonian Institute
Mammals* in rain forest
fragments
20
15
Intact forest
10
10 ha fragment
1 ha fragment
5
0
Mammals
Data from Lovejoy et al. (1984); in Nitecki, M.H.
“Extinctions”. Univ. Chicago Press
* These results are
from trapping
experiments and do
not include bats and
nocturnal canopy
species.
In intact forest 9
spp. were common;
in 10 ha fragments,
only one; in 1 ha
fragments, all
mammals were
“uncommon”.
Why conserve?
• Intrinsic and aesthetic value of
species (mosquitoes?)
• Economic value (gene pools,
untapped riches)
Bird species
The rewards of conservation
100
90
80
70
60
50
40
30
20
10
0
Saved
Extinctions
1500's
1600's
1700's
1800's
*
1900's
*Global data;
Source: New York Times Aug. 29, 2006; p. D3
Some of the saved
California condor
Mauritius parakeet
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Mauritius kestrel
Chatham Island taiko
Lear’s macaw
Species conservation: the
task ahead
“The threat ahead is massive. It’s like
we’ve ridden our first wave on a
surfboard and feel good about it, but look
back and there’s a tsunami coming in.”
Dr. Stuart Pimm, a conservation ecologist at Duke University,
quoted in the New York Times, Aug 29, 2006, p. D3.
How conserve?
• Zoos and captive breeding (e.g. condors)
• Predator control (e.g. Chatham Is. taiko)
• Habitat preservation / restoration
(e.g. Mauritius parakeet) for its own sake, or
combined with sustainable economic diversification
(e.g. turtle harvesting vs. cattle farming on the
Amazon floodplain; the former retains the galeria
forest).
• Compensation
e.g. ranchers in Wyoming [for cattle killed by wolves];
farmers in Bahia, Brazil [for corn eaten by Lear’s
parrot]
Predator control
Pre
Eradication scorecard (# island removals)
e.g. mammals (all alien) have been eradicated on 68 of the 168 islands in New
Zealand; 41 introduced mammal populations have been eradicated on 27
islands off the Pacific coast of Mexico. Native plant and animal species
have rebounded following eradications.
Source: Krajick. K. 2005. Science 310, p. 1410-1413.
Post
Predator control -> habitat restoration
goat exclosure
Pre
e.g. removal of goats on
Santiago Island (Galapagos)
leads to recovery of native
vegetation.
Source: Krajick. K. 2005. Science
310, p. 1410-1413.
Post
Species
need
space!
Based on surveys of avifauna in Amazonas
How big a fragment
would conserve 95%
of the species over
a 50-yr period?
Ans. = 100,000 ha.
[100 km x 100km!]
New Scientist 8-14 November, 2003, p.15;
Good choice
Applications
of island
biogeography
theory to
habitat
conservation
Poor choice
Corridors and conservation
• Experiment to determine effects of corridors between open
patches on plant biodiversity in longleaf pine (Pinus palustris)
forest in South Carolina. Patches created in 2000.
Source: Dametsch, E. et al., 2006. Science 313, 1284 -
Corridor experiment results
Connected patches have
~20% more plant spp. than
unconnected patches; few
weedy exotics
Source: Dametsch, E. et al., 2006. Science 313, 1284 - 1286
Do the ecological
reserves in BC
display these
principles?
Goosegrass Creek
(Kootenays)
E.R. #55
Haynes Lease
(Okanagan)
E.R. #100
1 km
Future challenges: climate change
In alpine areas timberline is creeping upwards by a few meters per
decade; alpine species are therefore occupying smaller and smaller
refuges. In NZ, for example, it is predicted that 80% of alpine
islands will be wiped out in this century, and 200-300 alpine plant
species will go extinct*. How do we develop conservation
strategies that are nimble enough to deal with climate change?
*Halloy, S.R.P., and Mark, A.F. 2003. Arctic, Antarctic, and Alpine Research, 35, 248-254.
A more local example of this problem….
1930
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Pika
(Ochotona princeps)
2006
Subalpine rodents,
(e.g. Zapus spp.)
are now found
700m higher than
they were a
century ago; the
altitudinal ranges
of Alpine
chipmunks and
pikas have shrunk
correspondingly
Pacific jumping mouse
(Zapus trinotatus)
Lassen Peak, northern California
Graphics: NY Times (Nov. 7, 2006); Wikipedia