The Evolutionary Mystery of Hibiscus Plants on Pacific Islands
What caused the greater percentage of orange hibiscus plants on an island after a volcanic lava flow?
A. Orange flowering hibiscus plants were better adapted to survive lava flows, so white hibiscus was naturally selected out of the population on the island.
B. The limited population size after the lava flow resulted in a limited gene pool, causing genetic drift in future generations of hibiscus plants on this island.
C. Cross pollination across the islands without the lava flow caused the percentage of orange flowers to dramatically change on these islands over time.
D. The hibiscus plants on the island that had the lava flow suffered from a higher mutation rate than plants on other islands, causing a difference in the populations.
Answer:
The correct answer is option B. The limited population size after the lava flow resulted in a limited gene pool, causing genetic drift in future generations of hibiscus plants on this island.
Genetic drift is an evolutionary mechanism in which the allelic frequencies in a population change through many generations. Its effects are more pronounced in a small-sized population. Genetic drift results in some allele loss, even those that are beneficial for the population, and the setting of other alleles, causing their frequency to increase. The final consequence is the random fixation of one of the alleles.
Genetic drift has significant effects on a population when it experiences a dramatic reduction in size due to a disaster (bottleneck effect) or a population split (founder effect). In the case of the hibiscus plants on the island affected by the volcanic lava flow, the natural disaster caused the loss of some alleles and the fixation of others. Among them, the allele that codes for orange hibiscus plants became fixed, leading to an increase in its frequency in the population.
By understanding genetic drift and its effects on population genetics, we can appreciate the role it plays in shaping the genetic diversity of species over time. It highlights the importance of population size and genetic variation in determining the evolutionary trajectory of a species.