A population of rodents, called population A, lived together in harmony on a large landmass until one group of the population dispersed to a nearby island. Two million years later, the island population is split into two smaller, equal-sized populations when a river formed across the middle of the island. Now two new species have evolved on the island, A1 and A2. They have replaced the population from which they were derived. Which represents the phylogeny of the populations discussed in this scenario?
A)diagram M
B)diagram H
C)diagram K

Question

A population of rodents, called population A, lived together in harmony on a large landmass until one group of the population dispersed to a nearby island. Two million years later, the island population is split into two smaller, equal-sized populations when a river formed across the middle of the island. Now two new species have evolved on the island, A1 and A2. They have replaced the population from which they were derived. Which represents the phylogeny of the populations discussed in this scenario? 
A)diagram M 
B)diagram H 
C)diagram K

Quizplus · Accepted Answer

This scenario describes a single population (A) that diverges into two populations (A1 and A2) that eventually replace the original population. Therefore, the correct phylogeny would be represented by diagram C, which shows a single ancestral population (at the base of the "Y" shaped tree) that diverges into two descendant populations (represented by the tips of the "Y"). Diagrams M and H show different patterns of branching that do not fit with the scenario described.

A Population of Rodents, Called Population A, Lived Together in Harmony