Question

migrant Beetle reproduces with the local population as a result genes of migrant Beetle Enter the new population​

Answer 1

That’s the result of natural selection.
Migrant beetles reproduces only with migrants one

Consider Migrant beetles with white colour coat has been coloured by black due to the industrial smoke around it ! And the colour coat has been changed from white to black similar to that of trunk of the tree .

Hence the changes in colour resulted them from being attacked by its predator ,so white coloured coated beetles and eaten up and remaining black coloured Beetles survived and hence they became dominant in the population

Answer 2

this phenomenon is speciation