Question

The island fox, Urocyon littoralis, is endemic to the Channel Islands, which are located off the coast of southern California. Six of the eight Channel Islands support fox populations, and each of these islands is home to a distinct subspecies, as shown in the table below.

	Island	Subspecies
Northern Channel Islands	Santa Cruz	U. l. santacruzae
	Santa Rosa	U. l. santarosae
	San Miguel	U. l. littoralis
Southern Channel Islands	San Nicolas	U. l. dickeyi
	San Clemente	U. l. clementae
	Santa Catalina	U. l. catalinae

The island fox shares a common ancestor with the gray fox, Urocyon cinereoargenteus, which is found on the mainland. Both species have similar coloration and a diploid chromosome number of 66. One structural difference between the two species is the reduced size of the island fox, a feature known as dwarfism. The various island subspecies also differ from each other in size, number of tail vertebrae, and other characteristics.

The phylogenetic tree below shows the evolutionary relationships between the island fox subspecies and the gray fox. Drag the labels to their appropriate locations on the tree.

First, drag the blue labels onto the blue targets to identify the common ancestors at the branch points.

Next, drag one white label onto the white target to identify the homologous characteristic.

Then, drag one pink label onto the pink target to identify the relationship between the two species.

Answer 1

a. common ancestor of gray foxes and island foxes

b. ancestor of Santa rosa and san Miguel foxes.

c. dwarfism

d. ancestor of northern channel island foxes

e. most closely related.

f. ancestor of southern channel island foxes.

g. ancestor of island foxes

h. ancestor of san Catalina and San Clemente foxes.