Question

Under what conditions do Aitken and Whitlock (2013) suggest that assisted gene flow (AGF) would be most beneficial? Least beneficial? (Hint: See Figure 1 of Aitken and Whitlock 2013.) Be sure to use your OWN WORDS.

--------------------- Large Increased number of climate-adapted alleles and genotypes Low genetic differentiation Little genetic effect of AGF Local population size Outbreeding depression Introduction of locally maladapted alleles EEEEEEEEEEEEEEEEHHHHHHHHHH.. Reduce inbreeding depression Demographic support - - - - - - - - - - - - - - Small Low High Natural gene flow Figure 1 Positive and negative effects of assisted gene flow (AGF) vary with historical levels of gene flow between source and recipient populations and with the size of the recipient population. Each box on this graph indicates a parameter combination for which certain genetic or demographic forces are important. The red box indicates that the risk of negative effects of outbreeding depression likely outweighs the potential positive effects of increased adaptive capacity, the white boxes indicate that positive effects likely outweigh negative effects, and the yellow box indicates lower-priority situations for AGF for which high natural gene flow likely provides sufficient variation for evolutionary rescue.

Answer 1

Beneficial:

1. Source population should be previously locally adapted to the climate conditions being experienced by the target population.

2.Foundation species should be chosen as increase in fitness of foundation species may have positive impacts on other species and communities.

3. Large populations are more suitable for evolutionary rescue through AGF since they will have significant diversity required for adaptaton.

4. Populations in topographically variable regions can be able to gain from AGF as they can migrate relatively short distances and possess genetic diversity which can be attributed to gene frlow from differently adapted populations.

5. Presence of preadapted alleles increases the beneficial effects of AGF.

6. Natural gene flow should be low to moderate and the population should be large.

7. Natural gene flow should be moderate or high in cases of small population .

Least Beneficial :

1. In cases of populations already adapted to non-target environments, AGF can decrease fitness, lead to population decline, productivity loss and increase in chances of extinction of small population.

2. A major amount of Natural Gene Flow may lead in any direction and can cause maladapation.

3.When the source population differs in chromosome number or has subtle choromosomal differences such as inversions, choosing them for AGF can lead to maladaptation.

4. When local adaptation or locally adapted alleles do not correlate with the targeted environment , fitness is reduced and the beneficial effects of AGF are eroded by the introduction of maladapted alleles.

5. Introduction of foregin genotypes for AGF may result in loss of genetic lineages.

6. Species which can experience strong outbreeding depressing counterbalance the beneficial effects of AGF.

7. Invasion of long-isolated populations can result in AGF being least effective since they can result in outbreeding depression.

8. Large population with high amount of Natural Gene Flow can be harmful