Transcript ecopresfinal

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Chapter 11: Evolution
of Invaders
Nicolas Viveros and Issy Cless
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The Role of Transport In Evolution of Invaders
Three “rules of thumb” for how the specific
circumstances surrounding a non-native’s
introduction influence its genetic diversity
(relative to the native source population):
1.
2.
3.
Genetic diversity of a new population will likely be
lower if transport vectors sample only a very small
percentage of the native population’s variation.
Genetic diversity may be higher if introductions
sample from source populations with high
geographic genetic structure- admixture may
occur.
A population’s genetic diversity will be lost if the
population size is limited for long periods of time.
This occurs even with large propagule sizes.
Hybridization With Natives can increase
a species’ invasiveness by
-creation of novel genotypes
-high genetic variation that allows survival and
success under a wider range of conditions
-conferring hybrid vigor through the loss/masking
of deleterious alleles or fixed heterogeneity
These conditions are most often met with parental
taxa that are not too evolutionarily similar or too
dispirate.
Would this figure look different for non-plants?
 How do intentional introductions
differ from accidental introductions
in their effects on the new
population’s genetic diversity?
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 In what specific situations would
founding events cause a new
population to have increased
genetic diversity? Can you think of
any cases that we have discussed in
previous classes in which the nonnative population is likely to be more
genetically diverse than the source
population?
 What types of environments are
more conducive to a native species
having a high geographic genetic
structure? Can we use this as a tool
to predict which native regions are
more likely to produce successful
invasives?
 How can a small propagule size
contain more genetic diversity than
a large one? Why is propagule size
relatively unimportant in determining
the genetic variability of a
population?
 When examining a small population,
how can you determine whether a
shift in the gene pool is due more to
random genetic drift or to selection?
 Propose some mechanisms by which
the evolution of a non-native could
be slowed. Do you think a species’
post-introduction evolution is an
important catalyst in its growth and
spread as compared to other
potential catalysts such as
environmental disturbance, etc.?
 What is the timescale for which you
would expect evolution of an
invader to occur? Can you
accurately predict this timescale
from information gathered about
the species in its native habitat?
How do varying timescales effect
non-natives’ ability to spread and
their impacts on natives?
 Do you think the intermixing of
subsequent generations of hybrids
would result in further increases in
genetic variability or in decreases?
 What are some specific
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mechanisms for how
character
displacement works
and why it is
evolutionarily beneficial
for the species
involved? How might
character
displacement
exacerbate certain
invasion scenarios?
 How might we be able to use
population and evolutionary
genetics to our advantage to
prevent the growth and spread of
non-native populations?