R24 Evolution of biodiversity

Question 1

What are some trends in species diversity and biodiversity across the tree of life, spatially and temporally ?

Answer 1

Species diversity is unevenly distributed across the tree of life
Species diversity is not evenly distributed in space
Biodiversity is not evenly distributed through time

Question 2

How can we study long term patterns of diversification ?

Answer 2

• Fossil data: most biodiversity that has evolved as since gone extinct
  o Fossil record is coarse (families not species) and incomplete
• Molecular phylogenies: molecular phylogeny calibrated with fossil data
  o Mammalian families originated before the cretaceous/Paleogene boundary 66Mya

Question 3

What is the diversification rate equal to ?

Answer 3

D=S – E

• Speciation at rate S, extinction at rate E

Question 4

What is D when there is exponential growth ?

Answer 4

more than 0

Question 5

The rate in the formation of lineages is equal to ?

Answer 5

Diversification rate x number of lineages

Question 6

What plot is used to plot a number of lineages through time ?

Answer 6

LLT plot

Question 7

What is the steepness of the number of lineages (both actual and surviving ?

Answer 7

D

Question 8

What is shown by a large upturn in the number of surviving lineages ?

Answer 8

A large upturn in the number of surviving lineages  a lot of young lineages have not had time to go extinct

Question 9

How could we measure sexual conflict in insects ?

Answer 9

• The differences in the variance in offspring numbers between males and females
• The fraction of genome that has sex biased expression
• The number of mates a female has e.g., polyandry vs monandry
• Asymmetry in parental care

Question 10

What is evidence for a slowdown in diversification ?

Answer 10

shown by the shorter branches to the tips. The number of niches or possible species may be limited

Question 11

What does a constant positive diversification rate show ?

Answer 11

exponential growth in the number of species

Question 12

How can we identify traits that matter for diversification?

Answer 12

• Sister clade comparisons: testing whether a trait is associated with a change in diversification requires independent replicates
• Herbivory evolved independently in the ancestors of weevils and leaf beetles and moths and butterflies
  o Their herbivorous clades are much more species rich than their sister clades
  o Could be due to chance N=2, only 2 contrasts could be due to chance
  o Increase the number of comparisons, decreases chance that it’s down to chance.
• Herbivory defences are also more species rich

Question 13

What is co-speciation ?

Answer 13

key traits correlated with diversification often have to do with biotic interactions, co-evolution can lead to fast change
- Often imperfect, obligate mutualism, significant but imperfect co-phylogenetic pattern, only one species of wasp can pollinate figs