Lecture 12: Applied Evolution

Question 1

What is the relevance of evolution to agriculture?

Answer 1

Pesticide and herbicide resistance. Weeds reduce crop yield by 34% (billions of dollars of losses). Weedy plants have repeatedly evolved resistance to herbicides.

Question 2

What is the relevance of evolution to medicine?

Answer 2

Developed resistance to antibiotics. Some gene mutations can lead to drug resistant tumours. How do we create an evolution proof vaccination?

Question 3

Where does resistance come from and why does the source matter?

Answer 3

1. pre-existing genetic variation in population (what we do doesn’t affect this
2. New mutations: in very large populations new simple mutations may be introduced at high rate (we can try to reduce population size)
3. epidemic spread of resistance from one region to the next (we can try to reduce gene flow).

Question 4

Julia Kreiner

Answer 4

grad student at u of t studying outcrossing weeds. Findings show that outcrossing weeds are more capable of resistance than selfing weeds. Evolution of water-hemp herbicide resistance is a result of pre-existing genetic variation, new mutations in large pop, and epidemic spread of resistance from region to region.

Question 5

How might herbicide resistance be stopped?

Answer 5

• multi herbicide treatment makes new adaptations promoting resistance less likely to occur as it must be much more complex to be resistant to all of the herbicides at once. The mutation would not likely be able to target multiple genes at once.
• rotation of different kinds of herbicides means weeds are constantly hit by different selection pressures (although this could potentially cause generalized resistance among population)

Question 6

Major prevention strategy for malaria

Answer 6

Insecticides. However, resistance to these develops. If we can figure out how to target mosquitoes later in life (after reproduction) it would reduce the transmission without also creating selective pressures.

Question 7

How does evolution pertain to HIV and cancer treatment?

Answer 7

Drug cocktails slow evolution of HIV (similar to multi herbicide use). Less aggressive treatments also reduce evolution of resistance by reducing selective pressures. The time you take the drugs at also REALLY matters.

Question 8

Glyphosate Resistance

Answer 8

Existed in one county in southern Ontario in 2010 and spread to over 40 by 2014

Question 9

Normal extinction rate of species and extinction rate with human pressures

Answer 9

Extinction is a normal process and in undisturbed ecosystems the rate is approx. 1 species every 10 years. The current rate is 4000-6000 species per year (particularly in tropical regions).

Question 10

Genetic issues in conservation biology

Answer 10

few individuals are rebuilding populations of species. Founder effects…

• loss of genetic diversity
• loss of heterozygosity
• inbreeding depression
• fixation or deleterious alleles
• inability of populations to adapt

Question 11

Species with fewer than 30 individuals left

Answer 11

Speke’s Gazelle (4), Siberian Tiger (25), European Bison (13), Indian Rhino (17)

Question 12

What does the probability of adaptation depend on?

Answer 12

Population size, rate of adaptation, strength of selection against common genotype (how fit is the wild type).