Apple maggots are a type of fly native to North America. Prior to the introduction of the apple tree to North America, apple mag
gots fed from and laid their eggs on hawthorn trees. After apple trees were introduced, some apple maggots began feeding from and laying their eggs on apple trees. Adult apple maggots will only mate on the type of tree on which they were born. What is the most likely consequence of the introduction of apple trees to apple maggots?
A.
Some apple maggots will undergo adaptive radiation to colonize many other types of trees besides the apple and hawthorn.
B.
Populations of apple maggots that mate on different trees could become reproductively isolated and eventually speciate.
C.
Apple maggots that are born on apple trees will be unable to reproduce and will eventually die out.
D.
Individual apple maggots will eventually learn to lay eggs on both hawthorn trees and apple trees.
B is the most likely consequence because of the following facts we are told:
After apple trees were introduced, some apple maggots began feeding from and laying their eggs on apple trees
Adult apple maggots will only mate on the type of tree on which they were born.
This provides a geographical isolation (because they are feeding and laying eggs on separate trees) and reproductive isolation (because they will only mate on the type of tree on which they are born).
These two factors increase the chances that apple maggots feeding on apple trees will only encounter those who have mated on the same tree, and continue to mate this way. Over time, the populations (i.e. apple tree vs hawthorn tree) will intermix less and less. This will mean the genetic pool will become distinct, and natural selection will be acting differently (different habitats and different genes), encouraging speciation.
Adult apple maggots mate on the type of tree on which they were born. Because apple trees were recently introduced, the adult maggots had to have been born on hawthorn trees, where apple maggots used to lay their eggs. Other apple maggots mate on apple trees. The two groups of maggots will not reproduce with each other because they prefer to mate on different trees. This type of reproductive isolation is called behavioral isolation, a difference in mating behavior that prevents organisms from reproducing with each other. This reproductive isolation will eventually result in speciation, or the creation of new species through physical separation.
