Complex sentence: Each of the species in a pest species complex has to be investigated separately from the others, and the species boundaries also define the limits to the spread of insecticide resistance or any genetically controlled traits that are inherited through sexual reproduction.
Split into simpler sentences: Each of the species in a pest species complex has to be investigated separately from the others. Species boundaries also define the limits to the spread of insecticide resistance or any genetically controlled traits that are inherited through sexual reproduction.