Answer:
The distribution of that trait in the population will change, probably decreasing to near zero.
Explanation:
An evolutive force such as natural selection is acting on this population.
Natural selection is the result between the individual phenotype and the environment that determines the destiny of genes. It results in adaptation, which means the increase of the aptitude phenotype.
Aptitude (or fitness) is reflected by the phenotype that results in the survival, fertility, and capability of having a mate. Aptitude is the contribution of each genotype to the next generation. It is a way of measuring the individual ability to leave fertile offspring. Aptitude must be significant to the natural selection act in its favor.
Natural selection can act favoring an allele or against it, according to how it affects the fitness of individuals.
When many organisms in a population sharing the same trait die, this is because they did not have good fitness, so they were not adapted to the environment and its pressures. The alleles coding for that trait were not good for the fitness of the animals, so they do not get to survive.
These individuals die before reproducing, so they could not transfer their genetic charge to the following generation. Eventually, the alleles coding for the trait will decrease in the population, probably near zero. Natural selection is acting against this phenotype. Other alleles will be beneficiated, and their frequency in the population will increase.
This change in alleles frequency is what we call adaptation.
