Marine diversity: the paradigms in patterns of species richness examined

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Marine diversity the paradigms in patterns of
species richness examined

• John S. Gray
• Biological Institute
• University of Oslo
• Norway

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Marine Diversity Paradigms(from Levinton 1995 p
347-9)

• 1. The best known diversity gradient is an
  increase of species diversity from high to low
  latitudes in communities of shelf benthos, and in
  the plankton
• 2. In both benthic and water column assemblages
  the open sea tends to have more species than do
  inshore habitats
• 3. Diversity of macroinvertebrates and fish
  increases with depth to just seaward of the
  continental rise and then decreases towards the
  abyssal plain.

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Data (number of species) on which paradigm of the
Latitudinal Diversity Gradient is based
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Latitudinal Gradient in Fossil Foraminifera
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Sanders Diversity Data (1968)
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The problems with rarefaction
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Important Questions

• Do the data really represent the biodiversity of
  the given area/habitat?
• Are the comparisons in diversity being made at
  the correct scale?

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Whittakers scales of diversity

• Point diversity - a single sample
• ? diversity - samples within a habitat
• ? diversity - the diversity of a larger unit
  (landscape or island)
• ? diversity - the total diversity of a group
  of areas of gamma diversity

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What recent data show
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Deep-sea data from New Jersey, USA, Grassle
Maciolek 1992
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Species diversity of deep-sea
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Diversity and Depth in the Deep Sea (Etter
Grassle 1992)
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Benthic Megafauna and Depth
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Southern Norway, Jøssingfjord
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Snorre oil field, Norway
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Frigg oilfield, Norway
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Port Phillip Bay, Australia
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Bass Strait, Australia
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Coastal data, Australia and Norway
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The species area relationshipFrigg S 152.69
230.88(LogA) R2 0.9975.
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Species diversity of coastal sediments
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Conclusions The Shallow-Deep Gradient

• The number of individuals per species is much
  lower in the deep sea (mean 52) than at the coast
  (mean 335 )
• Species density (number of species per unit area)
  is higher in the deep sea than coast
• Species richness decreases below 1500-2000m
• Coastal areas have a greater number of habitats
  than the deep sesa and overall must have higher
  species richness

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Latitudinal Diversity in the Deep Sea (Rex et al
1993)
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Latitudinal gradient of estuarine benthos
(Attrill et al 2001)
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Biodiversity of Norwegian continental shelf
(Ellingsen Gray 2001
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Alpha and Gamma species richness
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Beta and gamma species richness
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Latitudinal Diversity Gradient(from Roy et al
1998)
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Coral reef species richness (Veron, 1995)
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Bivalve species richness (Crame, 2000)
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Bivalve species richness (Crame, 2000)
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Conclusions from Crames study

• Old bivalve clades do not show a latitudinal
  gradient
• Young clades (especially the heteroconchs) show
  steep latitudinal gradients
• This suggests that species arise, primarily in
  the tropics (China-Indonesian region), and
  radiate from here
• Low Arctic species richness is probably because
  the species have not yet reached there.

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Approximate species numbers in the Southern
Ocean, (from Arntz et al 1997)
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Hypotheses of the Latitudinal Diversity Gradient

• Biological interactions Sanders Stability-Time
  hypothesis
• SpeciesArea Rosenzweig (1995) states that the
  tropics cover more area than any other zone and
  therefore, will have a higher number of species
• Total (or average) energy input is higher in the
  tropics and decreases polewards (Wright, 1983)
  and leads to higher species richness in the
  tropics
• Species rang sizes (Rapoports rule, 1982)
  species ranges are smaller in tropical than
  boreal and polar areas
• Evolutionary age. The tropics are a cradle or a
  museum of high species richness (Stenseth 1984
  Chown Gaston 2000 Crame 2000)

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Sanders Diversity Data (1968)
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The Stability-Time hypothesis
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Conclusions biological interactions

• No clear and testable hypotheses relating to
  species richness have been developed
• Regional species richness is correlated with
  local richness
• This suggests that local scale biological
  processes are unimportant in determining species
  richness (Lawton, 1999)

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Hypotheses of the SpeciesArea Relationship
(Rosenzweig 1995)

• Larger areas contain greater numbers of species
• Larger areas contain a greater number of habitats
• Larger areas have greater numbers of individuals
  and hence of species also

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SpeciesArea plot of Sanders data (from Abele
Walters 1978)
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Species area relationship for benthos of the
Norwegian continental shelf
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Area of Shallow and Deep Sea(from Rohde 1997)
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Relative Surface Areas of Oceans(from Rohde 1997)
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Latitudinal Diversity Gradient(from Roy et al
1998)
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Rohdes area data

• In the North Atlantic the subtropics has the
  largest area of all categories
• This is precisely where Roy et als data showed
  highest species richness in the North Atlantic
• However, in the Pacific the tropics has the
  largest area, which does not fit with Roy et als
  data, where maximal species richness is at 15o
  30oN

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Shelf Area and Prosobranch Diversity(from Roy et
al 1998)
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Conclusions on species area

• For small numbers of samples the species area
  relationship is SC X(LogA)
• For areas where sampling is very complete the
  relationship is LogS LogC X(LogA)
• Yet the species area relationship cannot
  explain the latitudinal gradient of species
  richness

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The energy-productivity hypothesis (Wright 1983)

• On land the available energy is maximal in the
  tropics and shows a decline polewards and this
  gradient is also shown in species richness.
• The correlates of energy are measures of heat
  such as mean annual temperature, mean summer
  temperature, sea-surface temperature or
  evapotranspiration

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Wrights energy-productivity hypothesis
Wright based his arguments first on the
assumption that the total number of individuals
of all species at a site should be proportional
to its area giving   N ? A  where ? is the
total density of individuals per unit area, and N
is the total number of individuals which is
proportional to the total production of available
energy at the site, E.   This gives
N ? E  where ? is
the number of individuals supported per unit rea
of energy.   This gives a species-energy curve S
kEz   or log S z logE Log k   where k is
a constant related to ? and S and z are as in the
species area relationship.  
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Mean Annual SST and Diversity(from Roy et al
1998)
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Species accumulation curvesNorwegian
continental shelf
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Biodiversity of Norwegian continental shelf
(Ellingsen Gray 2001
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Europe 125,000 b.p. Temperature 2oC warmer than
today (from Andersen Borns 1997)
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Europe 20,000-17,000 years b.p.(from Andersen
Borns, 1997)
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Europe and Arctic 15,000 years b.p.(from
Andersen Borns, 1997)
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Europe and Arctic 11,000-10,000 years b.p. (from
Andersen Borns, 1997)
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Species ranges Norwegian continental shelf
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The Unified Neutral Theory of Biodiversity Hubbel
2001
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Norwegian Continental Shelf 810 species
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Conclusions on the marine latitudinal gradient of
species richness

• Northern hemisphere low species richness occurs
  in the deep Norwegian Sea and high species
  richness occurs around 20oN with lower richness
  near the equator. Whether this relates to the
  energy hypothesis remains to be thoroughly
  tested.
• Southern hemisphere high species richness occurs
  in soft sediment benthos of Australia and
  Antarctica, and there is no clear cline of
  decreasing richness towards the equator.

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Trawl marks at 700m on the Skagerrak seabed
(Side-scan sonar picture from Thomas Lundalv)
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References

• The key references for this talk are shown below.

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