Evolution, 4th Edition

PHylogENy: THE UNITy ANd dIvERSITy of lIfE 407

Futuyma Kirkpatrick Evolution, 4e

Sinauer Associates

Troutt Visual Services

Evolution4e_16.06.ai Date 02-14-2017

A

A

A

A

T T Sp 1 Sp 2 Sp 3

Sp 1 Sp 2 Sp 3

Sp 1 Sp 3 Sp 2

(A) Sp 1

(B) T T A

(C) T A T

Sp 2 Sp 3 FIGURE 16.6 Incomplete lineage sorting can

cause gene trees to have a different topology

than the phylogeny of the species from which

the genes are sampled. At left, the species

trees (phylogenies) for three species are repre-

sented by the hollow branches, and the gene

trees by the solid colored lines inside them. At

right, the gene trees have been straightened

out to show the relations between the species

that they imply. (A) The ancestor of all three

species was fixed for A at a site in the genome.

After the first speciation event, a mutation from

A to T occurs in one gene copy in the popula-

tion (red bar). The copies inherited by species

2 and species 3 carry T. The gene tree agrees

with the species tree. (B) At a second site in the

genome, another mutation changes an A to a

T. Copies with the T are inherited by species 1

and species 2. This produces a gene tree that

does not agree with the species tree. (C) At a

third site, yet another mutation changes an A to

a T. This mutation is inherited by species 1 and

species 3. The gene tree that results is again

inconsistent with the species tree.

Futuyma Kirkpatrick Evolution, 4e

Sinauer Associates

Troutt Visual Services

Evolution4e_16.07.ai Date 02-14-2017

M. marshalli

M. oregonensis

M. montanus

M. triangularis

mt

N1

N2

N3

N4

N5

FIGURE 16.7 A phylogeny of four species

of grasshoppers (Melanoplus) inferred from

samples of five gene copies at each of six loci

within each species. Gene trees for the mito-

chondria and five nuclear loci (at right) differ

in many ways from the best estimate of the

species phylogeny (black outer lines), indicat-

ing that each of these four species inherited

several gene lineages from the common

ancestor of all four species. The diagram at

left shows all six gene trees nested within the

species phylogeny. (From [4], courtesy of L. L.

Knowles.)

16_EVOL4E_CH16.indd 407 3/22/17 1:33 PM