02.05.2013 Views

Evolution__3rd_Edition

Evolution__3rd_Edition

Evolution__3rd_Edition

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

450 PART 4 / <strong>Evolution</strong> and Diversity<br />

Divergence (%)<br />

40<br />

30<br />

20<br />

10<br />

changes at the same site become common the phylogenetic information in the<br />

sequence similarity is lost a a stopwatch with only a seconds hand would be no use in<br />

comparing professors’ lecture times. Likewise, slowly evolving molecules are useless<br />

for fine phylogenetic resolution because they will not have changed enough.<br />

(a) Mitochondrial ribosomal RNA gene (b) Nuclear ribosomal RNA gene<br />

0<br />

0 100 200 300 400 500 600 700<br />

0<br />

0 200 400 600 800 1,000<br />

Time (Myr)<br />

Time (Myr)<br />

(c) Cetaceans (d) Major animal groups<br />

Porpoises<br />

Dolphins<br />

Sperm<br />

whales<br />

Baleen<br />

whales<br />

Beaked<br />

whales<br />

Other<br />

mammals<br />

Figure 15.16<br />

Matching the molecule to the phylogenetic problem. The<br />

ribosomal RNA genes in the mitochondria (a) evolve more<br />

rapidly than those in the nucleus (b). The different points are<br />

for species pairs, for which the date of their common ancestor<br />

can be estimated from fossils. The graphs tail off (at about 33%<br />

divergence) because of multiple substitutions at a site.<br />

Divergence (%)<br />

80<br />

60<br />

40<br />

20<br />

Odontoceti<br />

Mysticeti<br />

Odontoceti<br />

Coelenterates (2)<br />

Chordates (4)<br />

Echinoderms (4)<br />

Insects<br />

Millipede<br />

Chelicerate<br />

Crustaceans (3)<br />

Oligochaete annelid<br />

Polychaete annelid<br />

Pogonophore<br />

Brachiopod<br />

Chiton<br />

Nudibranch mollusk<br />

Bivalve mollusks (2)<br />

Sipunculid<br />

(c) Phylogeny of dolphins and whales, using mitochondrial<br />

rRNA genes; the deepest root is about 35 million years ago.<br />

(d) Relations of major animal groups, as revealed by nuclear<br />

rRNA genes; the deepest root is probably over 600 million<br />

years ago. Redrawn, by permission of the publishers; (a and b)<br />

from Mindell & Honeycutt (1990), (c) from Milinkovitch et al.<br />

(1993), and (d) from Lake (1990).<br />

..

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!