Question

Refer to the figure below. You are studying a remote island before and after a volcanic eruption. Data at time 1 was collected one month before the eruption, and data at time 2 was collected one month after the eruption. All of the species on the island are endemic. The island is 100 km across. Species A and B (the two snail species) generally only move a distance of 2 m a day. Species C (the bird) often covers 20 km a day in search of food. After the eruption, the lava flow hardens, and the island is divided by a 20-km strip of bare rock with few if any resources these animals need to survive.

Figure 1.

Species A (snail) Species B (snail) Species C (bird) Time 1 Volcano Time 2 Active volcano Lava flow

Would you expect to see a change in patterns of gene flow in species B and C? Why or why not?

Deaths of individuals due to the volcanic eruption could change the frequency of alleles in these very small island populations. However, you do not have data on the allele frequencies before and after the eruption for any of these species. Based on your understanding of genetic change, do you expect that these three species would be affected by genetic drift? Why or why not?

Based on your knowledge of gene flow, genetic drift, and speciation, what do you predict will happen over the long term to these species? Do you predict that the current species will remain the same species, or do you think they might split? How would you be able to determine whether a species had split into two new species?

Answer 1

Yes, there might be a change in gene flow pattern in species B but not really in species C because after the lava flow, the species C will still be able to fly without the geographical boundary causing any massive change. However when it comes to the snail, since it moves only 2cm a day, it will find it difficult to move and overtime it will lead to change in genetic pattern due to the geographical barrier. With different conditions and limited resource, each of the species will tend to adapt to their surrounding environment and hence it might lead to change in gene flow. There might be migration of the species and hence cause a separation between the species from the same population causing the gene flow.   

It can lead to genetic drift when there is random variation within genotype of a particular population and hence it might lead to disappearance of some genes or some individuals. There is random sampling amongst organisms and hence due to the volcano, many species might die reducing the population and hence it can change the frequency of the existing variations of gene. Yes, there is a high possibility that the three species are affected by genetic drift because there is reduction in number of the population and hence it might separate the species from one another due to the lava hardening.

There is a possibility that after hundreds or thousands of years there might be speciation of the snail species due to the geographical barrier cause due to the lava hardening. Since the species will be separated, due to their gradual evolution and their adaptation to different areas and environment characteristics, they might develop different characteristics. The species which has split to form two species can be identified through phylogenetic analysis.