Lecture 12 Flashcards
3 main methods in which evolution may be applied
- agricultural relevance; pesticide and herbicide resistance
- evolutionary medicine; evolution of resistance to antibiotics, evolution-proof vaccination
- global change and evolution; adapt or go extinct
what is the problem with pests and evolution?
- we use chemicals to combat pests and pathogens
- we create strong selective pressure for resistance, with fitness advantage to resistant genotypes arising from mutation and gene flow
why are weeds an issue for agriculture?
- cause approx. 34% loss of crop yields annually
- compete with crops for light, nutrients, space
- usual solution is to spray with herbicides; however, weedy plants have repeatedly evolved resistance to herbicides
where does herbicide resistance come from?
- pre-existing genetic variation in the population
- new mutations - in very large populations new, simple mutations may be introduced at a high rate
- gene flow - epidemic spread of resistance from one region to the next
what type of weeds has the greater pre-existing resistance variation?
outcrossing weeds have more pre-existing resistance variation than selfing weeds
how can herbicide resistance be stopped
- multi-herbicide treatment
- makes new adaptation less likely
- requires more complex adaptation - rotation of different kinds of herbicides
- weeds regularly hit by different selection pressures
- but could select for generalised resistance
give a graph for time vs population size of endangered species and weedy plants
what is the problem with malaria and mosquitoes?
- malaria causes approximately 700,000 deaths annually
- major prevention strategy is insecticides
- strong selective pressure on mosquitoes has led to rapid evolution of resistance
what could be evolution-proof solutions to malaria?
- tailor insecticide application to knowledge of mosquito generation times and spacial distributions
- goal: minimise selection for mosquito resistance while still reducing malaria transmission
use HIV treatment as an example of evolution in medicine
- multi-drug cocktails slow evolution of HIV resistance
- single mutations unlikely to confer resistance to multiple drugs with different mechanisms of action
- lower viral loads make multiple mutations less likely
describe evolutionarily informed cancer treatment
- strong, prolonged selection pressures using the same chemotherapy drugs - may not be the best solution as it selects for resistance
- cycling drugs, multi drug cocktails, lower drugs - may be a better option but ethical considerations make tests of theory for human application challenging
describe environmental change as a problem
- loss of habitat
- habitat fragmentation
- altered abiotic conditions (temperature, precipitation, pH)
- altered biotic composition (transport of species, invasive species)
define extinction
permanent elimination of a species
genetic issues in conservation biology caused by environmental change
- loss of genetic diversity
- loss of heterozygosity
- inbreeding depression
- fixation of deleterious alleles
- inability of populations to adapt
probability of evolutionary rescue from adaptation depends on
- population size
- beneficial mutation rate
- how much fitness was reduced
