In this investigation of evolution in Hawaii, you will use actual genetic data from 18 species of Hawaiian drosophilid flies to construct an evolutionary tree that depicts evolutionary lines of descent for four of those species. These species belong to a group of about a hundred well-studied species known as the picture-winged drosophilids that have prominent black markings on their wings. Once the tree is complete, you will use it along with information about the geology of the Hawaiian islands to propose a series of events that could explain the current distribution of the four species.

• Student Reading

• Data Tables summarizing chromosomal inversions in 18 species of picture-winged drosophilids

First, you need to gain experience drawing an evolutionary tree and relating that diagram to specific genetic events. As shown in Figure 1, phylogenetic trees depict the evolution of two or more descendant species from a single ancestral species, with lines connecting the ancestral species to the descendant species. In the drosophilid flies of Hawaii, these descendant

Figure 1

An evolutionary tree of the living groups of mammals demonstrates their relationships, though some of the details of the tree remain controversial or ambiguous. A representative member of each group is shown in parentheses after the group name. In addition to the groups shown here, other mammalian groups have gone extinct. (Diagram adapted from Colin Tudge, The Variety of Life: A Survey and Celebration of All the Creatures That Have Ever Lived. New York: Oxford University Press, 2000.)