Tree thinking in scholarship biology

Rob CruickshankDepartment of Ecology

Lincoln University

“Just as beginning students in geography need to be taught how to read maps, so beginning students in biology should be

taught how to read trees and to understand what trees communicate”

Robert O’Hara 1997

What is a phylogenetic tree?

What is a phylogenetic tree?

What is a phylogenetic tree?

1837

“The most important diagram in

biology”

Steve Jones2009

What is a phylogenetic tree?

1859

Variations on a theme

Variations on a theme

Variations on a theme

Variations on a theme

Variations on a theme

Variations on a theme

These trees are identical

Which tree is different?1

Part 1

How to read a phylogeny

Which of the four phylogenies shown below depicts a different pattern of relationships to the others?

2

Which of the four phylogenies shown below depicts a different pattern of relationships to the others?

3

Which of the four phylogenies shown below is false given the larger phylogeny above?

4

If you were to add a trout to the phylogeny shown above, where would its lineage attach to the rest of the tree?

5

Part 2

How to infer shared ancestry

Which of the five letters in the phylogeny above corresponds to the most recent common ancestor of a

mushroom and a sponge?

6

Part 3

How to interpret relationships

According to the phylogeny shown above, which of the following statements is true?A A green alga is more closely related to a red alga than to a moss.B A green alga is more closely related to a moss than to a red alga.C A green alga is equally related to a red alga and a moss.D A green alga is related to a red alga, but is not related to a moss.

7

According to the phylogeny shown above, which of the following statements is true?A A crocodile is more closely related to a lizard than to a bird.B A crocodile is more closely related to a bird than to a lizard.C A crocodile is equally related to a lizard and a bird.D A crocodile is related to a lizard, but is not related to a bird.

8

According to the phylogeny shown above, which of the following statements is true?A A seal is more closely related to a horse than to a

whale.B A seal is more closely related to a whale than to a

horse.C A seal is equally related to a horse and a whale.D A seal is related to a whale, but is not related to a

horse.

9

Part 4

How to infer evolutionary change

In the phylogeny shown above, assume that the ancestor had a long tail, ear flaps, external testes and fixed claws. Assuming all evolutionary changes are shown, what traits do sea lions have?A Long tail, ear flaps, external testes and fixed claws B Short tail, no ear flaps, external testes and fixed claws C Short tail, no ear flaps, abdominal testes and fixed claws D Short tail, ear flaps, abdominal testes and fixed claws E Long tail, ear flaps, abdominal testes and retractable claws

10

In the phylogeny shown above, assume that the ancestor was not a tree and did not have leaves or seeds. Assuming all evolutionary changes are shown, which of the tips is a tree without leaves?A Lepidodendron D Psilotum B Clubmoss E FernC Oak

11

Part 5

Common mistakesand how to avoid them

Living organisms are not primitive

“It is absurd to talk of one animal being

higher than another”

Charles Darwin 1837

Living organisms are not primitive

Living organisms are not primitive

Living organisms are not ancestors

Humans are not descended from

chimpanzees, rather humans and

chimpanzees share a common ancestor that was neither a

human nor a chimpanzee

Lineages are not basal

Lineages are not basal

Lineages are not basal

Lineages are not basal

Lineages are not basal

An example

LinksTree thinking challenge

http://www.tree-thinking.org/publications.html#science310

Downloadable graphic image of the tree of lifehttp://www.zo.utexas.edu/faculty/antisense/downloadfilestol.html