latitudinal gradients
DESCRIPTION
1500. 1200. 900. Number of species. 600. 300. 0. -80. -40. 0. 40. 80. Latitude. Latitudinal gradients. Species – latitude relationship of birds across the New World show the typical pattern of increased species diversity towards the equator. Coral reef fish. Labridae. - PowerPoint PPT PresentationTRANSCRIPT
Latitudinal gradients
Species – latitude relationship of birds across the New World show the typical pattern of increased species diversity towards the equator.
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-80 -40 0 40 80
Latitude
Num
ber o
f spe
cies
020406080
100120140
0 100 200Distance from center of
diversity
Spe
cies
0102030405060
0 100 200Distance from center of
diversity
Day
s of
pel
agic
la
rval
dur
atio
n
0102030405060
0 100 200Distance from center of
diversity
Spe
cies
05
101520253035
0 100 200Distance from center of
diversity
Day
s of
pel
agic
la
rval
dur
atio
n
Coral reef fish
Labridae
Pomacentridae
Diversity of coral reef fish declines from their centres of diversity. There is also a strong correlation between distance and duration of the pelagic
phase, which is a proxi of dispersal ability.
Mora et al. 2003
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Latitude
Spe
cies
Latitudinal gradient in species diversity of mollusks on North and South American Pacific shelves (Valdovino et al. 2003)
• Centers of diversity are often shifted north or south • Species richness sharply declines towards temperate regions• Tropics contain a very large proportion of total species richness• Species near the center of species richness are often less dispersive
The general patterns
Hillebrand (2004) conducted a meta-analysis about 581 published latitudinal gradients
Variable Local samples Regional samplesBody size 0.0001 0.001Thermoregulation 0.74 0.88Dispersal type 0.11 0.03Trophic level 0.03 0.0001Longitude 0.08 0.0001Hemisphere 0.32 0.08Realm 0.01 0.0001Habitat 0.0002 0.0001Grain 0.14 0.69Range 0.82 0.99Global richness 0.24 0.37
Data obtained from
Latitude
Spe
cies
rich
ness
z
Scale
Regional
Local
Latitude
Spe
cies
rich
ness
z
Global richness
High
Low
Latitude
Spe
cies
rich
ness
z
Body size
High
Low
Latitude
Spe
cies
rich
ness
z
Trophic level
High
Low
Latitude
Spe
cies
rich
ness
z
Longitude
Atl, NW
Pac, In, EuA, AuA
Latitude
Spe
cies
rich
ness
z
Realm
Terrstrial, Marine
Freshwater
Basic conclusions• Nearly all taxa show a latitudinal gradient• Body size and realm are major predictors of the strange of the
latitudinal gradient• The ubiquity of the pattern makes a simple mechanistic explanation
more probable than taxon or life history type specific
Counterexamples
These taxa are most species rich in the northern Hemisphere
Soybean aphid, Photo by David VoegtlinThe sawfly Arge coccinea, Photo by Tom Murray
The ichneumonid Arotes sp., Photo by Tom Murray
The aquatic macrophyte Hydrilla verticilliata, Photo by FAO
Some theories that try to explain observed latitudinal gradients in species diversity.
Older theories:Environmental stabilityor predictability (Klopfer 1959)Productivity(Slobodkin and Sanders 1969)Heterogeneity (Pianka 1966)Latitudinal decrease in angle of sun ( Terborgh 1985)Aridity (Begon et al.. 1986)Seasonality (Begon et al.. 1986)Number of habitats (Pianka 1966)Latitudinal ranges (Rapoport 1982)Area (Connor and McCoy 1979)
Circular explanations:Competition ( Dobshansky 1950)Predation Paine 1966)Niche width (Ben Eliharu and Safriel 1982)Host diversity(Rhode 1989)Epiphyte load (Strong 1977)Population size (Boucot 1975)
Time related explanations:Temperature dependence of chemical reactions (Alekseev 1982)Temperature dependent mutation rates
Evolutionary time (Pianka 1966)Ice age refuges (Pianka 1988)
Energy related explanations:Energy supply (Rhode 1992)
Range size related explanation:Random range sizes (Colwell and Hurtt 1994) (Gillooly et al. 2005)
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-80 -60 -40 -20 0 20 40 60 80Latitude
SRed data points: Multihabitat gradient
in ant species diversity
Blue data points: Gradient for one habitat type
North American grasshoppers
Latitudinal gradients can also be found within single habitat types
Habitat heterogeneity
Energy or area per se
Ant species richness is significantly correlated to mean annual temperature and mean primary production, but not to area
Refuge theory
The refuge theory of Pianka tries to explain the gradient in species diversity from ice age refuges in which speciation rates were fast. This process is thought to result in a
multiplication of species numbers in the tropics. In the temperate regions without refuges species number remained more or less constant.
-80-60-40-20
020406080
-80 -60 -40 -20 0 20 40 60 80
Latitude
T
Max T
Min T
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Latitude
D T
Temperature difference
Species diversity and temperature
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0 10 20 30
Mean temperature
Spe
cies
rich
ness
z
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0 10 20 30
Mean temperature
Spe
cies
rich
ness
z
Western Atlantic gastropods Eastern Pacific gastropods
Biodiversity and temperature
Species diversity of marine gastropods is significantly correlated with mean surface water temperature
Metabolic theory and species latitudinal gradients in species richness
3/ 4 E / kT E / kT3/ 4 3/ 4
M M 1M W e e ln E / k CW W T
Body weight corrected energy use should exponentially scale to the inverse of temperature.
The slope –E/k should be a universal constant for all species independent of body size.
Biological times should scale to body weight to the quarter power
Examples: Generation time, lifespan, age of maturation,
average lifetime of a species
E1/ 4 ktt w e
The inverse of time are rates.
Examples: Growth rates, mutation rates, species turnover rates, migration rates
Hence biological rates should scale to body weight and temperature by
E1/ 4 kt1r w e
t
The rate of DNA evolution predicted from metabolic theory
3/ 4 E / kT 1/ 4 E / kTMM W e W eW
Body size specific metabolic rate M/W should scale to the quarter power to body weight and exponentially to temperature
Now assume that most mutations are neutral and occur randomly. That is we assume that the neutral theory of population genetics (Kimura 1983)
DNA substitution rate a should be proportional to M/W1/ 4 E / kTM / W W ea a
1/ 4 E 1ln( W ) Ck T
a
• Body weight corrected DNA substitution rates (evolution rates) should be a linear function of 1/T with slope –E/k = -7541
• Higher environmental temperatures should lead to higher substitution rates (faster evolution)
• Body weight corrected DNA substitution rates (evolution rates) should decrease with body weight
• Large bodied species should have lower substitution rates (slower evolution)
kT 1ln( e ) ln(W) C4
a
3/ 4 E / kT 3/ 4 E / kTM W e ; N W e NM C
Diversity and temperature
The energy equivalence rule
3/ 4 E / kT 3/ 4 E 1NM NW e C ln(NW ) ck T
The average abundance N of an assemblage of S species and J individuyals in areal A is N=J/SA
3/ 4 E / kT
3/ 4 E / kT
JB NM W e CSA
J W eSCA B
J E 1ln(S) ln( )k TCAB
For standard areals and species of similar body size holds therefore
E 1ln(S) Ck T
• Species richness should increase with environmental temperature
• Species richness should increase with energy
• The slope of this relationship should be -E/k = -7541K
Caveats:• Mean abundance per unit area is
independent of temperature. • The energy equivalence rule holds at least
approximately and its slope is independent of temperature.
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0.0032 0.0034 0.0036 0.0038 0.004
1/T
S
S=e
z=-10005
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0.003 0.003 0.003 0.004 0.004 0.004
1/T
S
z=-8540
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0.0032 0.0034 0.0036 0.0038 0.004
1/T
S
z=-10250
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0.0033 0.0034 0.0035 0.0036 0.0037
1/T
S
z=-10810
North American
trees
Costa Rican trees along an elevational gradient
North American
amphibians
Ecuadorian amphibians
Fish species richness Prosobranchia species richness Ectoparasites of marine teleosts
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0.0032 0.0034 0.0036 0.0038 0.004
1/T
S
z=-9160
0200
400600800
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0.0032 0.0033 0.0034 0.0035 0.0036 0.0037
1/T
S
z=-7170
0
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25
0.0033 0.0034 0.0035 0.0036 0.0037
1/T
S
z=-8510
Latitudinal gradients: http://en.wikipedia.org/wiki/Latitudinal_gradients_in_species_diversity
Gaston K. 2000 - Global patterns in biodiversity - Nature 405: 220-227
Allen A. P., Brown J. H., Gillooly J. F. 2002. Global biodiversity, biochemical kinetics, and the energy equivalence rule. Science 297: 1545-1548.
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