Lecture 11 - Macroecology & latitudinal diversity

Question 1

latitudinal diversity gradient

Answer 1

Alexander von Humboldt

• more species at lower latitudes
• temperature gradient
• area = more land at lower

Question 2

LDG exceptions

Answer 2

gymnosperms peak away from equator

- ldg masks more subtle distributions

Question 3

Climatic factors - energy + productivity

Answer 3

• potential evapotranspiration
• ectotherms = extra warmth, enhances food intake
• endotherms = less use to maintain body temp, more for growth/reproduction
• narrower range species co-exist

Question 4

Climatic factors - spatial and habitat heterogeneity

Answer 4

more different niches, support wider species range

more species with smaller niches co-exist

Question 5

Plants at Hood river, Canada

spatial habitat hetero

Answer 5

• Douglas fir structural diversity + spider species
• fish richness + vegetation
• ant + tree richness

Question 6

Historical factors (evolution)

Answer 6

are global richness patterns due to past variation

- net diversification = speciation - extinction

Question 7

Tropical cradles

historical

Answer 7

tropics home to young, rapidly evolving lineages

- speciation peaks - extinction invariant with latitude

Question 8

Tropical museums

Answer 8

home to old, relictual species

- speciation invariant - extinction declines in tropics

Question 9

Out of tropics

Answer 9

formed in tropics, moved to extratropics
- speciation peaks - extinction declines

supported by phylogenetic evidence in mammals

Question 10

Ecogeographical rules

Answer 10

variation in traits are over geographical/environmental gradients

Question 11

Bergmann’s rule

Answer 11

body size increases at high latitudes in mammals

• reduces heat loss
• temperature gradient
• orders at low temps = widest temp range

Question 12

geographic distribution bird body mass

Answer 12

median mass highest at low temperature

• small bodied = species rich areas
• large bodied = poor areas
• patterns driven by thermoregulation, taxanomic turnover, community assembly

Question 13

Allen’s rule

Answer 13

appendages length in closely related endothermic vertebrates increase in hotter environments
- bill size declines with latitude and altitude, increase at minimum temperature

Question 14

Jordan’s rule

Answer 14

number of vertebrae in fish increase toward higher latitude

• linked to body size
• strong pattern in non-migratory fish

Question 15

Thorson’s rule

Answer 15

main development switches from pelagic in tropics, to direct at higher latitudes

• pelagic = larvae disperse in ocean current
• direct = no dispersal

direct = more likely to become geog isolated, speciate at higher latitudes

Question 16

Gloger’s rule

Answer 16

darker pigmentation in hot, humid zones

• birds
• few tests, little support

Question 17

Rapport’s rule

Answer 17

smaller species range at lower latitudes

- many tests, differing support