Textbook Problem

Hawaiian Honeycreeper Phylogeny The po'ouli (Melamprosops phaeosoma) was discovered in 1973 by a group of students from the University of Hawaii. Its membership in the Hawaiian honeycreeper clade had been controversial, mainly because its appearance and behavior are so different from other living honeycreepers. It particularly lacked the "old tent" odor characteristic of other honeycreepers.

In 2011, Heather Lerner and her colleagues deciphered phylogeny of the 19 Hawaiian honeycreepers that were not yet officially declared to be extinct at the time, including the po'ouli. The researchers sequenced mitochondrial and nuclear DNA samples taken from the honeycreepers, and also from 28 other birds (outgroups). Phylogenetic analysis of these data firmly establishes the po'ouli as a member of the clade, and also reveals the Eurasian rosefinch as the clade's closest relative (FIGURE 18.10).

FIGURE 18.10 Phylogeny of Hawaiian honeycreepers. This cladogram was constructed using sequence comparisons of mitochondrial DNA (whole genome), and 13 nuclear DNA loci of 19 Hawaiian honeycreepers and 28 other finch species.

Which species on the cladogram represents an outgroup?

Summary Introduction

To determine: The species on the cladogram that represents an outgroup.

Concept introduction: Cladogram is a diagram that represents the hypothetical relationship between different groups of animals known as phylogeny. It is used to visualize the similarities and commonly shared characters of different groups of animals. A cladogram uses lines to demonstrate branches that end at a clade. A group of animals whose members possess one or more derived characters is called as a clade.

Answer to Problem 1DAA

Correct answer: Eurasian rosefinch (Carpodacus) species on the cladogram represent an outgroup.

Explanation of Solution

As given in the problem statement, membership of the po’ouli (Melamprosops phaeosoma) was controversial in Hawaiian honeycreeper clade when it was discovered in 1973. Later in the year 2011, the researchers deciphered phylogeny of 19 Hawaiian honeycreepers including the po’ouli. They sequenced mitochondrial and nuclear DNA samples from the honeycreepers and 28 other birds (outgroups). A outgroup is a reference group of organisms where the phylogenetic tree would be rooted. Refer Fig. 18.10, “Phylogeny of Hawaiian honeycreepers”, in the textbook. The cladogram was made using the comparison of mitochondrial DNA (whole genome) and 13 nuclear DNA loci of 19 Hawaiian honeycreepers and 29 other finch species. On the basis of the tree, Eurasian rosefinch (Carpodacus) species are visualized as common ancestors, and thus they represent an outgroup.