Latitudinal Gradient & Hyperdiverse Places

Question 1

what is the latitudinal gradient of biodiversity

Answer 1

there are a lot more species in the tropics than the poles - taxonomic, phylogenetic, functional or genetic diversity’s relationship with latitude

Question 2

list the spatial scales of biodiversity

Answer 2

alpha, beta and gamma diversity. There is also delta and gamma but they are uncommonly used.

Question 3

what is alpha diversity

Answer 3

total count of local species

Question 4

what is beta diversity

Answer 4

change/turnover between adjacent habitat types

Question 5

what is gamma diversity

Answer 5

total count of species in a landscape

Question 6

issues with beta diversity in academic journals

Answer 6

can be calculated many ways, so must be careful when comparing

Question 7

which diversity type changes with latitude

Answer 7

alpha and gamma

Question 8

why is the impact of latitude on beta diversity negligible

Answer 8

limited dispersal along one latitude, environmental controls, local stochastic processes. Tropical species have narrow temp ranges, so small elevation changes can completely separate populations

Question 9

key readings for latitudinal gradient of latitudinal gradient

Answer 9

hillebrand 2004, miraldo et al 2016

Question 10

issues with studies into latitudinal biodiversity gradient

Answer 10

smaller studies when viewed individually may refute it, but when all the studies are combined and analysed, even ones that don’t show a strong/significant relationship with latitude now do

Question 11

exceptions to latitudinal biodiversity gradient

Answer 11

smaller studies when viewed individually may refute it, but when all the studies are combined and analysed, even ones that don’t show a strong/significant relationship with latitude now do

Question 12

key sampling issues when analysing latitudinal biodiversity gradient

Answer 12

more sampling in UK and US than tropics, so we have to correct for lack of sampling in tropics

Question 13

was the latitudinal gradient present in dinosaurs

Answer 13

most dino species were in the temperate zone, not the tropics

Question 14

why is there a latitudinal gradient now, if there has not always been

Answer 14

maximal richness in the tropics coincides with glacials, and temperate zone for interglacials

Question 15

why is it difficult to study causes of latitudinal biodiversity gradient

Answer 15

“many variables also vary with latitude,
no way to replicate the earth in a lab, can’t do manipulative reasoning,
scientists keep adding more slightly different hypothesis to get something names after them
difficult to separate hypotheses in the lab”

Question 16

why do some propose geographical area as the cause for the latitudinal biodiversity gradient

Answer 16

“more land near equator

maybe more land = more individuals = more chance for speciation

maybe more chances to form niches and this leads to less extinction”

Question 17

why do some propose that more functional area in the tropics is the cause for the latitudinal biodiversity gradient

Answer 17

“tropics region has more consistent temperatures than other regions

tropics are closer to more land than temperate and polar regions”

Question 18

why is evidence for geographical area as the cause for the latitudinal biodiversity gradient unclear

Answer 18

diversity in biomes on different continents is correlated with size, but freshwater fish in large areas have fewer species than small areas in the tropics

Question 19

why do some propose more energy in the tropics as the cause for the latitudinal biodiversity gradient

Answer 19

“tropics have more solar radiation, higher temperature, more rain and evapotranspiration, less variable seasonality.

Therefore, more productive and less stress, so more individuals. Also allows faster generation times, so more speciation”

Question 20

which forcings need to be modelled when explaining the latitudinal biodiversity gradient?

Answer 20

“High speciation or immigration to tropics

Low extinction or emigration from tropics”

Question 21

what are the 3 major tropics speciation models

Answer 21

tropics as cradle’ model, ‘tropics as museum’ model, ‘out of tropics’ model

Question 22

what is the tropics as cradle model

Answer 22

origination rates are higher in tropics, while extinction rates do not vary with latitude

Question 23

what is the tropics as museum model

Answer 23

origination rates are constant with latitude, while extinction rates are lower in the tropics

Question 24

what is the out of the tropics model

Answer 24

origination rate is higher in the tropics AND extinction rates are lower in the tropics, BUT species movement is higher from the tropics to other latitudes

Question 25

reading for out of tropics model

Answer 25

Jablonski et al 2016, bivalve molluscs

Question 26

what does diversity begets diversity mean

Answer 26

once an area is diverse, additional species can specialise on the niches formed by that diversity

Question 27

which ecological processes are important to analysing the LGoB

Answer 27

Rapoport’s rule, rescue effects, productivity of aseasonality effects

Question 28

what is Rapoport’s rule

Answer 28

environmental conditions vary a lot less in the tropics, so a species doesn’t need to be able to tolerate a wide range of temperatures across the year

Question 29

what is the rescue effect

Answer 29

smaller ecological niche sizes allows more perimeter, so organisms from one niche can interact or migrate to another t prevent extinctions

Question 30

how does aseasonality of the tropics impact productivity

Answer 30

more production, more individuals, more species, lower local extinction

Question 31

from an evolutionary standpoint, how do hot wet tropics have more biodiversity

Answer 31

out of tropics theory, conserves niches better, hotter = faster speciation = more evolution, diversity begets diversity. Therefore, hot wet aseasonal environments promote higher net diversification rates

Question 32

from an ecological standpoint, how do hot wet tropics have more biodiversity

Answer 32

higher productivity, frost free environment, no moisture stress - rapoport rule. Therefore, hot, wet, aseasonal environments allow more species to persist

Question 33

what is the mid domain effect

Answer 33

if lots of species geographical domain overlap over one region, that region will have high species richness.

Question 34

reading for mechanisms controlling LGoB

Answer 34

Brown 2014

Question 35

how will climate change effect LGoB

Answer 35

“hotter world has flatter gradient (like dinos)

if bc more species can survive in temperate zone, can they keep up with fast changes

if bc less species in hotter tropics, biotic attrition”

Question 36

how will habitat conversion and deforestation effect LGoB

Answer 36

“tropics lose more species per unit area, so flatter gradient
organisms cant migrate away from tropics bc habitat loss in temperate zone”

Question 37

4 types of hyperdiverse systems

Answer 37

tropical rainforests, mesic savannas, tropical freshwater systems, shallow water coral reefs

Question 38

most hyperdiverse regions

Answer 38

tropical mountains

Question 39

how accurate is our understanding of tropical hyperdiversity

Answer 39

v underestimated, we’re still finding 15000 new species a year

Question 40

what conditions do hyperdiverse systems need

Answer 40

high productivity, so high temperatures, water availability (if on land) or light availability (if in water)

Question 41

Facts about humid tropical forests

Answer 41

“10% of total earth’s ice free surface

33% global net primary productivity

store 25% of the biospheres carbon

sustain 1.2 billion people

strongly force global atmospheric circulation, generating clouds, transpiring water etc”

Question 42

reading for humid tropical forest diversity

Answer 42

slik et al 2015

Question 43

similarity in biodiversity of humid tropical forests globally

Answer 43

Amazon and Asia similar, African diversity much lower

Question 44

why are tropical forests in Africa less diverse

Answer 44

Africa is drier than other continents, so during glaciation the forests shrink to refugia and only adaptable species have survived

Question 45

Facts about wet savannahs

Answer 45

“highly productive

mix of trees and grass

wet and dry season, so leaf fall

wildfire prone

Question 46

interchangeable names for wet savannahs

Answer 46

mesic savannah, cerrado, dry forests

Question 47

facts about freshwater habitats

Answer 47

“some are wetlands, some are large rivers or river fed lakes

often very under researched”

Question 48

facts about shallow water coral reefs

Answer 48

“marine structures cleated by symbiosis of algal zooxanthellae symbionts and calcifying small animals

powered by sunlight and warm temperatures, so need shallow clear water

0.1% of earth surface, but contain 25% f all marine species

275 million people fish there

coastal protection for 197 million people”

Question 49

why are tropical mountains hyper hyper diverse

Answer 49

high beta AND gamma diversity

Question 50

environmental controls on tropical mountain biodiversity

Answer 50

“moist windward side, dry leeward side (due to watershed)

different light levels and aspects

complex topography allows microhabitats

soil fertility changes with altitude”

Question 51

Ecological controls on tropical mountain hyper hyper diversity

Answer 51

“high regional species pool

Rapoport’s rule - smaller ranges, so smaller temperature changes

each environmental control is strong, so wont move much, so can pack a lot of species onto a mountain”

Question 52

Evolutionary controls on tropical mountain hyper hyper diversity

Answer 52

“even as climate changes, it just goes up or down the mountain, so species can more, thus lower extinction

mountains provide a more effective barrier in the tropics bc species there tend to have lower tolerance for conditions outside their niche”

Question 53

how many types of rarity

Answer 53

7 - depending on geographic range, habitat specificity, & local population size

Question 54

main threats to hyperdiverse systems

Answer 54

habitat loss, habitat degradation, homogenisation, climate change