Transcript Presentación de PowerPoint - International Census of Marine

Robert May
ecologist
We have a catalog of all the
celestial bodies our instruments
can detect in the universe, but …
Photo: Hubble Telescope
… we ignore how many living
beings share the Earth with
us
Census of Marine Life
The known, the unknown and the knowable
O’Dor & Gallardo 2005 Scientia Marina (modified from Falkowski & de Vargas 2004)
www.icm.csic.es/scimar
O’Dor & Gallardo
Yarincick & O’Dor
2005 Scientia Marina 69 (Suppl 1)
The known:
about 6000 species of prokaryotes
about 80000 species of protists
What is the
unknown?
How many “taxons” of microbes are
there?
How much room for unknown taxons is there?
1. Numbers
2. Niches
1 cm3
105 prokaryotic
cells
1 dm3
108 prokaryotic
cells
Most clone
libraries
Yungas
Nothofagus forest
1 m3
1011 prokaryotic
cells
Venter’s study of
Sargasso Sea
Equivalent to 2 x 106 km2 of trees
1.4 x 109 km3
1029
prokaryotic
cells
The whole ocean
1st Postulate:
The number of microbial cells is enormous
Morse et al.: Nature
More niches as size decreases due to fractal
structure of nature
Purple sulfur bacteria
H 2S
SO4
e-
CO2
Lake Cisó (Girona)
OM
Purple sulfur bacteria:
Usually several species coexist in
nature
Growth rate (h-1)
Van Gemerden (1974)
90
C.vinosum
C.weissei
80
70
Percent of cells
60
50
40
30
20
6 hours light / 6 hours dark
10
0
2
4
6
Time (days)
8
10
12
Van Gemerden (1974)
0,6
Dark
Light
0,5
0,4
C.vinosum
Sulfide
C.weissei
Sulfur
C.weissei
Sulfide
0,3
C.vinosum
Sulfur
0,2
0,1
0
-50
0
50
100
Time (h)
150
200
2nd Postulate
The number of potential niches is very large
How many taxons of bacteria are there in the
sea?
Only a few
thousand
Hagström et al. Appl. Env.Microbiol. 68, 3628–3633 (2002).
Perhaps two
million
Curtis et al. Proc. Natl Acad. Sci. USA 99, 10494–10499 (2002).
The species difference between related communities
suggests that the number of species of bacteria may be more
than a THOUSAND MILLION.
… speciation in bacteria is easy and extinction difficult,
… giving a rate of speciation higher than the rate of extinction,
… leading to an ever increasing number of species over time.
FACT
The abundance of individuals in microbial species is so large
that dispersal is rarely (if ever) restricted by geographical
barriers
AND COROLLARY (FICTION?)
… global species number is relatively low
Science (2005) 310: 1878
3th Postulate:
The number of microbial taxons is VERY large
Range: 103 to 106 (perhaps even 109) taxons
T.L. Erwin 1991
ecologist
Determining the
number of species
today is like reaching
for the stars; there is no
way with the data
available today that we
are even going to get
reasonably close
Photo: National Geographic
Ramon Margalef
ecologist
Biodiversity vs diversity
Ramon Margalef (1997) Our Biosphere, Excellence in Ecology Series 10
Biodiversity is the dictionary
Diversity is the words used in a book
Individuals
Biodiversity = Diversity + “Seed bank”
Diversity
“Seed bank”
Taxon number
Two kinds of taxons
Molecular techniques
Individuals
Culture techniques
Diversity
Seed bank
Taxon number
Individuals
Biodiversity = Diversity (Knowable) + “Unknowable”
Diversity
Difficult to know
Taxon number
Diversity
Seed bank
BIODIVERSITY
How much room for species is there?
1. Numbers
2. Niches
All the marine bacterioplankton-derived 16S
ribosomal DNA sequences … were analyzed
When … dereplicated by using 97% similarity as a
cutoff, 1117 unique ribotypes were found.
We conclude that the apparent bacterioplankton
species richness is relatively low.
Analysis of many clones from 10 sampling sites
… dominant ribotypes were few (5 in average) and
they were often already retrieved in previous analysis
In contrast, a large part of each library was new or
never found in previous studies… majority of rare
ribotypes were specific to each location (I.e.
endemic)
..surprisingly low global diversity (around 2000
ribotypes)
T. Pommier, B. Canbäck, K. Hagman, L. Riemann, K. Simu, A. Tunlid & Å.
Hagström (in preparation)
How much room for species is there?
1. Numbers
2. Niches
It is sufficient to estimate the area under the species-area
curve for a given environment
Number of spp can be calculated from the total number of
individuals and the abundance of the most abundant
members
On a small scale:
Oceans 160 per mL
Soils 6400-38000 per g
On a large scale:
Whole Oceans 2 x 106
1 Tm Soils 4 x 106
Science (2005) 310: 502
Data from Rosenzweig et al. (1994) Genetics 137:903
Redrawn by Dykhuizen (1998) Ant. Van Leuuwen. 73:25