Geographic variations in microbial cytometric diversityGeographic variations in microbial cytometric diversity

William LiWilliam Li

Bedford Institute of OceanographyBedford Institute of Oceanography

CanadaCanada

William Li William Li reviewed some of the recent reports in the literature that address issues reviewed some of the recent reports in the literature that address issues

surrounding microbes and spatial scaling. He pointed out that a compilation of extant surrounding microbes and spatial scaling. He pointed out that a compilation of extant

microbes listed in textbooks might fall short of a true census because the concept of species is microbes listed in textbooks might fall short of a true census because the concept of species is

problematic. Bill outlined recent studies on soil fungi and salt marsh bacteria in which the problematic. Bill outlined recent studies on soil fungi and salt marsh bacteria in which the

taxa-area relationships were used to extrapolate from local to regional scales. The slopes of taxa-area relationships were used to extrapolate from local to regional scales. The slopes of

these relationships were low, indicating that taxonomic richness is not greatly dissimilar at these relationships were low, indicating that taxonomic richness is not greatly dissimilar at

different scales, suggesting a ubiquitous distribution of many microbes. However, more different scales, suggesting a ubiquitous distribution of many microbes. However, more

recent studies of bacteria in water-filled treeholes and of phytoplankton in limnetic and recent studies of bacteria in water-filled treeholes and of phytoplankton in limnetic and

marine systems indicate that the slopes are much higher in non-contiguous habitats. In other marine systems indicate that the slopes are much higher in non-contiguous habitats. In other

words, diversity at local scales may not be easily extrapolated to the global scale. The taxa-words, diversity at local scales may not be easily extrapolated to the global scale. The taxa-

area issue remains unresolved for marine microbes. Bill suggested that Alan Longhurst’s area issue remains unresolved for marine microbes. Bill suggested that Alan Longhurst’s

concept of the biogeochemical provinces in the ocean might be one way to focus our census concept of the biogeochemical provinces in the ocean might be one way to focus our census

efforts. This approach has been used to scale up primary production from the regional to the efforts. This approach has been used to scale up primary production from the regional to the

global scale. For the census of marine microbes, it therefore seems worthwhile to understand global scale. For the census of marine microbes, it therefore seems worthwhile to understand

the patterns and mechanisms that relate microbial diversity to primary production.the patterns and mechanisms that relate microbial diversity to primary production.

““The taxa-area relationship … was relatively flat (slope z=0.074) … This suggests that despite high local The taxa-area relationship … was relatively flat (slope z=0.074) … This suggests that despite high local diversity, microorganisms may have only moderate regional diversity.” (diversity, microorganisms may have only moderate regional diversity.” (Green et al. 2004 Nature 432:747-750Green et al. 2004 Nature 432:747-750).).

Spatial scaling of microbial soil fungiSpatial scaling of microbial soil fungi

““The The zz-values for bacteria … are among the lowest … for any organisms, suggesting that turnover of bacterial -values for bacteria … are among the lowest … for any organisms, suggesting that turnover of bacterial taxa at these spatial and taxonomic scales may be lower than that of most other organisms.” (taxa at these spatial and taxonomic scales may be lower than that of most other organisms.” (Horner-Devine et Horner-Devine et al. 2004 Nature 432:750-753al. 2004 Nature 432:750-753).).

Spatial scaling of salt marsh sediment bacteriaSpatial scaling of salt marsh sediment bacteria

““Bacterial genetic diversity in this system increased with increasing island size according to the familiar Bacterial genetic diversity in this system increased with increasing island size according to the familiar species-area power law (Fig. 1A). The slope z of the relationship (z = 0.26) is indistinguishable from published species-area power law (Fig. 1A). The slope z of the relationship (z = 0.26) is indistinguishable from published values for larger organisms (Fig. 1B). The data show that area size strongly influences the diversity of these values for larger organisms (Fig. 1B). The data show that area size strongly influences the diversity of these microbial communities.” (Bell microbial communities.” (Bell et al. 2005 Science 308:1884et al. 2005 Science 308:1884).).

Spatial scaling of bacteria in water-filled treeholesSpatial scaling of bacteria in water-filled treeholes

““Phytoplankton species richness thus scales smoothly and consistently from laboratory microcosms to the Phytoplankton species richness thus scales smoothly and consistently from laboratory microcosms to the world’s oceans, with 74% of the observed variance in world’s oceans, with 74% of the observed variance in SS being attributable to variations in ecosystem surface being attributable to variations in ecosystem surface area alone. area alone. zz-value = 0.134 ” (-value = 0.134 ” (Smith et al. 2005 PNAS 102:4393-4396Smith et al. 2005 PNAS 102:4393-4396).).

Spatial scaling of phytoplankton (laboratory cultures to oceans)Spatial scaling of phytoplankton (laboratory cultures to oceans)

““Both Both and and -components of species diversity are size-dependent: there are many more species in smaller -components of species diversity are size-dependent: there are many more species in smaller size classes in any one local community, but at a global scope the situation changes drastically.” (size classes in any one local community, but at a global scope the situation changes drastically.” ( Azovsky Azovsky 2000. Web Ecology 1:28-342000. Web Ecology 1:28-34))

Spatial scaling of small organisms – are they ubiquitous? - maybeSpatial scaling of small organisms – are they ubiquitous? - maybe

““Physical population isolation may be more common than is currently appreciated, as the ability to detect Physical population isolation may be more common than is currently appreciated, as the ability to detect isolation clearly depends upon the resolving power of the genetic marker(s) used and the habitats and isolation clearly depends upon the resolving power of the genetic marker(s) used and the habitats and organisms examined.” (organisms examined.” (Papke and Ward 2004Papke and Ward 2004))

Spatial scaling of small organisms – are they ubiquitous? – maybe notSpatial scaling of small organisms – are they ubiquitous? – maybe not

Biogeochemical provinces: a basis for examining geographic variationBiogeochemical provinces: a basis for examining geographic variation

Longhurst (1995) Ecological Geography of the Sea. Academic PressLonghurst (1995) Ecological Geography of the Sea. Academic Press

Biogeochemical provinces: a possibility to scale diversity through production?Biogeochemical provinces: a possibility to scale diversity through production?

data of data of Longhurst et al. (1995) Journal of Plankton Research 17:1245-1271Longhurst et al. (1995) Journal of Plankton Research 17:1245-1271

Area (106 km2)

0.1 1 10 100

Are

al p

rim

ary

pro

du

ctio

n (

g C

m-2

d-1

)

0.01

0.1

1

10

NWCSGFSTARCTBPLRNASENASW

Biogeochemical provinces: a possibility to scale diversity through production?Biogeochemical provinces: a possibility to scale diversity through production?

data of data of Longhurst et al. (1995) Journal of Plankton Research 17:1245-1271Longhurst et al. (1995) Journal of Plankton Research 17:1245-1271

Area (106 km2)

0.1 1 10 100

Pri

mar

y p

rod

uct

ion

(G

t C

y-1

)

0.1

1

10NWCSGFSTARCTBPLRNASENASW

P = 0.43 A0.46

““Diversity is a unimodal function of biomass or productivity” (Diversity is a unimodal function of biomass or productivity” (Irigoien et Irigoien et

al.)al.)

Diversity is maximum at intermediate levels of biomass or productivity because of nutrient or Diversity is maximum at intermediate levels of biomass or productivity because of nutrient or food limitation at low levels, and selective grazing or predation at high levels.food limitation at low levels, and selective grazing or predation at high levels.(Irigoien et al. 2004 Nature 429:863-867)(Irigoien et al. 2004 Nature 429:863-867)

Cytometric richness is maximum at intermediate biomassCytometric richness is maximum at intermediate biomass

Chlorophyll (mg m-3)

10-4 10-3 10-2 10-1 100 101 102

Cyt

om

etri

c ri

chn

ess

(S)

0

50

100

150

200NWCS z<20m

GFST z<20m

ARCT z<20m

BPLR z<20m

NASE z<20m

NASE upwelling z<20m

NASW z<20m

Chlorophyll (mg m-3)

10-4 10-3 10-2 10-1 100 101 102

Cyt

om

etri

c ri

chn

ess

(S)

0

50

100

150

200ALL z<200m

NWCS z<20m

GFST z<20m

ARCT z<20m

BPLR z<20m

NASE z<20m

NASE upwelling z<20m

NASW z<20m

data of data of Li (2002) Nature 419:154-157Li (2002) Nature 419:154-157