Question

You are an entomologist studying the population genetics of aphids. Aphids are insects that “suck” the phloem from plants. There is an aphid population on a milkweed plant outside your lab. You sample the aphid population, sequence their DNA and conclude that they are all genetic clones (i.e. genetically identical). This is possible because aphids parthenogenetically reproduce during the summer. Describe what would need to happen in order for this population to evolve. To earn full credit, you need to describe all the possible ways for evolution to occur.

Answer 1

The possible ways for evolution to occur are

1. Cyclical parthenogenesis- life cycle changes from sexual mode of reproduction (which results in new genotypic combinations) to female producing parthenogenesis (which results in rapid multiplication).

2. Horizontal gene transfer by bacterial symbionts of aphids

3. Mutations in gene which is an ultimate source of evolution. Rare beneficial mutations occur in this which may induce adaptation in the absence of recombination.

4. Adaptive potential to different environmental condition

5. Selective pressure on aphid population which is contributed by the changes in host plant quality, defense and availability impose.

6. High phenotypic plasticity (when exposed to varied environments, one genotype can produce more than one phenotype)

7. symbionts of aphids protects them from their enemies.