Fig - Fig Wasp Natural History
750 spp. of fig, most with
a single sp. of pollinator!!
http://129.31.3.171/index.html
Fig - Fig Wasp Model
MVP: ~ 170 fig trees are required to eliminate a gap in flowering
among trees - i.e., 99% probability of persistence for 1000 years.
Big-Blue Butterfly
An obligate parasite of ant colonies
Butterfly oviposits on thyme
Caterpillar becomes
a beautiful butterfly
Caterpillar is fed
by / feeds on ants
http://faculty.plattsburgh.edu/thomas.wolosz/metapop.htm
Caterpillar feeds
on thyme
Caterpillar enters
Myrmica ant nest
Big-Blue Butterfly
• First started disappearing in the 19th century
• Hypotheses
–
–
–
–
–
Over-collecting by insect collectors
Insecticides
Fragmentation
Climate change
Air pollution
• Rapid decline in the 1950’s, extinct by 1979.
Big-Blue Butterfly
BUTTERFLY
THYME
SHORT GRASSY FIELDS
ANT COLONY (Myrmica sabuleti)
GRAZING
MYXOMATOSIS
RABBITS
Migratory Birds
• Studies have identified a decrease in U.S.
neotropical migrants
– Decreasing at the rate of 0.5 to 1.0% per year
• Hypotheses
– Deforestation in tropics or breeding ground
– Susceptibility to predation or cowbird
parasitism on breeding grounds
Brown-headed cowbird
The Evidence
• Based on taxonomically diverse community in
eastern U.S.
– Decline of migrants equal to ~ 1% / year.
• Based on wood warblers, vireos, gnatcatchers,
kinglets, titmice, chickadees, nuthatches, brown
creeper, wrens, bluebirds across U.S.
– No decline for migrants
– Recent declines in birds with high susceptibility to
predation / cowbird parasitism
Black-Footed Ferret
The most endangered mammal in N. America
http://www.ngpc.state.ne.us/wildlife/ferret.html
Inter-relationship of species
“The number of bumblebees in any district
depends in a great measure upon the number of
field-mice, which destroy their combs and nests”.
“[Because] the number of mice is largely
dependent, as everyone knows, on the number of
cats . . . It is quite credible that the presence of a
feline animal in large numbers in a district might
determine, through the intervention first of mice
and then of bees, the frequency of certain flowers
in that district!” - Charles Darwin, On the Origin
of Species
Keystone Species
Photo by James M. Cook
Keystone Species
Species with a disproportionate effect on community structure.
Keystones
Dominants
Total Effect
strong
interactors
Common Cold
weak
interactors
Abundance
From: Meffe and Carroll
Problems with the Keystone
Species Concept
•
•
•
•
Loosely applied
Difficult to test
Questionable application
Conclusion: Focus on interaction strengths
Ecological Niche
abundance
• Grinnell (1917): where a species lives (habitat)
• Elton (1927): what a species does
• Hutchinson (1950s): combination of all biotic and abiotic
requirements of a species: n-dimensional “hyper-volume”
seed size
temperature
predator density
Competitive Exclusion
abundance
abundance
• If the niches of two competing species overlap by
“too much”, then one tends to replace the other.
• Corollary: Competition drives the evolution of
divergent niches or life-history strategies (i.e.,
respond or perish)
niche
niche
Darwin’s Finches:
Character Displacement
“The Ghost of Competition /
Predation Past”
• What we see today may be the result of
competition / predation in the past (i.e., implies
evolutionary history).
– Consider Pleistocene extinctions
• Conservation Implication: Exotic species may
have their most negative effects after invading
communities that lack an analogous evolutionary
partner