Which environmental factor would likely lead to an increase in genetic variation in a population of squirrels? an increase in predators an increase in available food an increase in forest fires an increase in pollution

"an increase in predators" would likely lead to an increase in genetic variation in a population of squirrels, since the squirrels would have to adapt to the new threats. 

Answer;
An increase in available food and and also decrease in predators would most likely increase the genetic variation in a population. 

Explanation; 
Genetic variation is essential for natural selection since the natural selection can only increase or decrease the frequency of alleles that already exist in the population. Genetic variation may be caused by mutations, and random mating between organisms. 
Increase in the available food also increases the genetic variation as organisms are able to interact freely and thus increases the chances of random mating.  

Maybe haha