Refer to the Figure

Refer to the figure.

-You are studying a remote island before and after a volcanic eruption. Data at Time 1 were collected one month before the eruption, and data at Time 2 were collected one month after the eruption. All of the species on the island are endemic. The island is 100 km across. Each animal icon represents 20 individuals. Species A and B (the two snail species) generally move a distance of only 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. What is the most likely explanation for what happened to species A as a result of the volcanic eruption?