Download Coevolution

Coevolution
How species adapt to each other
Species exist in a web of interactions
Coevolution: Reciprocal
evolutionary change
between interacting
species, driven by natural
selection
Interactions
Effect on fitness
Definition
Examples
Positive / Positive
mutualism
A relationship between
species that raises each
other’s fitness
Cleaners
Anemone Symbiosis
Positive / Neutral
commensalism
A relationship in which one Remoras on sharks
species benefits but the
other suffers no loss in
fitness
Negative / Positive
A relationship in which one Predators / Prey
species benefits but the
Deception
Host and parasite
other suffers a loss in
fitness
Coevolution requires genetic variation
SS, South to South (green,
solid line)
SN, South to North (blue,
dashed line);
NN, North to North (black,
solid line)
NS, North to South (red,
dashed line).
May, initial phenotypic values;
June, midpoint phenotypic
values (45 days); August, final
phenotypic values (90 days).
Genetic variation can fuel rapid evolution
Abundance of Synechococcus
cells (red solid line) and
infectious viral particles (blue
dashed line) over time
Host phenotypes detected at
six time points labeled by their
ability to resist infection
The viral phenotypes detected
at the same six time points,
numbered in their order of
infectivity
• detected between 4 and 13 newly evolved viral phenotypes
(differing in host range)
• Detected between 4 and 11 newly evolved Synechococcus
phenotypes (differing in viral resistance)
The strength of selection varies geographically
Response can be affected when traits have other costs
Number of mussels
consumed by Nucella in
foraging experiments
Final shell thickness of
Nucella raised with
waterborne cues from no
crab (control), Carcinus,
or native Cancer crabs.
Geographic mosaic theory of coevolution
Coevolutionary alteration can occur in interactions involving many species
Coevolutionary arms race
• Examples from experimental evolution
Coevolutionary arms races
•
•
Cost to coevolution
Prochlorococcus resistance to phage
results in lower genome size,
•
•
reduced growth, or resistance to infection
by other phages
Deceleration in arms race
Population decline of evolved resistant cultures during phage infection.
Growth of the R1 (A), R5 (B), and R8 (C) evolved cultures
Evolved(Ev; red) were compared with susceptible wild-type control strains (WT; black) and
initial resistant substrains (iR; blue) when infected with the P-TIP38 phage (filled circles).
They were also compared with growth of noninfected cultures (open circles).
Key Concepts
• The intensity and specificity of coevolutionary
interactions can vary geographically and over time
• Antagonistic interactions may involve frequencydependent selection that maintains genetic
variation
• Also applies to mutualistic relationships
Müllerian mimicry facilitates learned avoidance
Hypselodoris fontandraui (a), H.
villafranca (b), H. cantabrica
(c), H. picta (d), and H.
fontandraui everting its buccal
bulb in
aquarium on a sponge fragment
Batesian mimicry creates frequency dependent selection
Colour pattern changes in Stegostoma
fasciatum
d. Newborn Stegostoma fasciatum
swimming at the surface in shallow
inshore, turbid waters off the
Kimberley coastline of north-western
Australia
e. a sea snake on the swimming on the
surface in Shark Bay, north-western
Australia
Key Concepts
• Arms races result when antagonistic interactions
lead to directional selection on each species
• Strongly antagonistic interactions may evolve to be
less antagonistic over time
• When mutualistic species exert positive frequencydependent selection rapid coevolution can result
• Mutualisms are vulnerable to cheating
•
Long standing mutualisms often have mechanisms to
punish cheaters
Diversifying coevolution can accelerate divergence between
populations
Echinoderms
Myzostomida
Summers et al. 2014
Extinctions can disrupt mutualisms
Global preserved reef volume
constructed by corals in the
Mesozoic and Cenozoic plotted
at a stage-level stratigraphic
resolution.
Note logarithmic scale. Tr—
Triassic, J—Jurassic, K—
Cretaceous,
Pg—Paleogene, Ng—Neogene.
Ecological selectivity of coral extinctions at the
K–T boundary.
Extinctions rates depend strongly on feeding
mode with presumably zooxanthellae bearing
corals (z-like) being much more affected than
azooxanthellate corals (az-like).
Human impacts on species diversity
Broadnosed pipefish
Trematode
Effect of temperature on
proportion of lymphocytes
(A), proportion of monocytes
(B) and activity of
lymphocytes (C) for head
kidney cells of S. typhle
experienced a heat wave
(black boxes, 256C) and
control treatment (white
boxes, 186C).
Key Concepts
• Highly specialized mutualisms make species
dependent on each other
•
Extinction of one species may drive extinction of the
other