Lecture 10: Evidence for diveristy

Question 1

what is the evidence for J-C? how to test?

Answer 1

look at predictions and assumptions, remove natural enemies does the effect density-depended? YES, removes density dependence

Question 2

J-C: looking at assumptions removal of natural enemies:

Answer 2

remove natural enemies does the effect density-depended? YES, removes density dependence

Question 3

J-C: looking at assumptions host specialisation?

Answer 3

• there are more insect species in tropical forests than temperate
• herbivorous insects are no more specialised in tropics than temperate
• implying that diversity of insects is driven by tree diversity

Question 4

community level density dependence is tendency for ___ species to increase in abundance and ___ species to become rare

Answer 4

• rare
• common
• -> J-C generates this effect as a consequence of natural enemies

Question 5

neutral theory has __ density dependence

Answer 5

NO

Question 6

if density dependence is strong and inter-specific competition is weak, conditions for __ are fulfilled

Answer 6

coexistence

Question 7

prevalence of density dependence? simple experiment:

Answer 7

compare density of seedling recruits with density of seeds

Question 8

studies show; strength of D-d (resulting from natural enemies) correlates with

Answer 8

abundance

Question 9

Neutral theory: can u test it?

Answer 9

• no DIRECT evidence supporting it
• predictions look like real systems
• can be difficult to test using main predictions
• theoretically useful
• if diversity is regulates by natural enemies, then coexistence of competitors is not the the problem theory suggests
• -> Cannot be truly simple because of density dependance

Question 10

communities in tropical forests appear to be more ____ with a ___ diversity of interactions

Answer 10

• complex

- greater

Question 11

trophic networks in modified habitats are more ______

Answer 11

simplified