clonal diversity matters high levels of functional and genetic diversity occur in the model...
TRANSCRIPT
Clonal diversity mattersHigh levels of functional and genetic
diversity occur in the model microzooplankter Oxyrrhis marina
SSchool chool of of
BBiological iological SSciencesciencesSSchool chool of of
BBiological iological SSciencesciences
Chris Lowe, David Montagnes, Phill Watts
Microbial food webs are important in aquatic systems
Many morphospecies are thought to be ubiquitous
Phylogenetic data suggest this may be so (but results are ambiguous)
But are we looking at the right aspects?
Functional (phenotypic) diversity may be a more appropriate metric to assess distribution
Introduction
Redrawn from Conover (1982)
A well characterised morphospecies
A commonly used model organism
An easy organism to grow
Ubiquitous
Introduction: Oxyrrhis marina Dujardin 1859
10 µm
Distribution
“Everything is everywhere, nature selects”Are we adequately examining diversity?
MorphologyGeneticsFunctional differences (phenotypes)
Introduction: The BIG question
A specific test case: O. marina One morphospecies Phylogenetic markers (different)Ecophysiological responses (different)
Phylogeography: Distribution
Phylogeography: Our data
Phylogeography: (5.8s ITS rDNA)
18s 5.8s 24s
5` 3`ITS ITS
0.05 substitutions/site
Plymouth CAP1133/3
IOM/PSM
IOM/P
IOM/S
Bahrain CAP1133/4
Finland CCAP1133/5
Washington CCMP604
Caribbean CCMP1788
Connecticut CCMP1795
Florida CCMP605
Texas CCMP1739
100
100
100100
95
63
These are all Oxyrrhis (18s rDNA)
4 well-supported cladesLarge genetic differencesDo they have a phylogeographic
distribution?Lowe et al. 2005
Phylogeography: (5.8s ITS rDNA)
They have no clear phylogeographic distribution
Ecophysiology: Is distribution related to function?
Ecophysiology: Is distribution related to function?
Habitat Environment
Oxyrrhis marinaPools vs coastal watersSalinity
SalinityG
row
th r
ate
()
Salinity (ppt)
10 6030 40
0
1
-1
Time
nu
mb
ers
Nt = N0•et
Ecophysiology: salinity
Salinity (ppt)
Gro
wth
rat
e (
d-1)
Location
Geographical location
5.8s ITS sequence data
Habitat: coastal, intertidal
Ha
bit
at
Co
as
tal
There appears to be a habitat specific response
Ecophysiology and rDNA do not agree
2 growth rate responses
Lowe et al. 2005
Morphology: inadequate resolution “Neutral” markers: rDNA does not
explain observed distribution of clones
Is everything everywhere?
We need to examine multiple clones to assess differences
Ecophysiology: suggests distributional patterns based on habitat
Our next step is to examine:Selection/adaptation Population
structure/dispersalNeutral and Functional
characteristics
Interdisciplinary approach to biodiversity
Redrawn from Conover (1982)
Conclusion
Breaking boundaries: quantifying the influence of demography and
seascape in driving divergence in the protist Oxyrrhis marina
Phill Watts, Chris Lowe, David Montagnes
SSchool chool of of
BBiological iological SSciencesciencesSSchool chool of of
BBiological iological SSciencesciences
This is a hypothesis describing processes of:DispersalAdaptation
Oxyrrhis marina:
“Everything is everywhere, nature selects”
It suggested distributions of micro-organisms are fundamentally different from macro-organisms
To data there has been no explicit tests of this hypothesis for micro-organisms across landscapes
Distinct oceanographic boundaries (e.g. fronts, gyres, isthmuses, currents)
Strong environmental gradients (temperature, salinity)
The marine environment is heterogeneous
We will quantify relative roles of natural selection and random drift in driving divergence
Spatial variation in adaptive traitsi.e. salinity and temperature tolerance
Demographic parameterse.g. population boundaries, population sizes migration rates
Are these processes/parameters different between micro-organisms and macro-organisms?
Oxyrrhis marina:
The heterogeneous marine environment provides a framework to examine adaptive/neutral variation
Oxyrrhis marina and the marine environment
Collect O. marina samples from across Europe
2 scales: Northern EuropeIrish and Celtic seas
For each site:Isolate & culture replicate O. marina clones Genotype isolatesMake phenotypic measurements Growth rate Cell size Gene expression (Na/K ATPase, HSP)
Oxyrrhis marina and the marine environment
Gene expression
Gen
etic
an
d p
hen
oty
pic
div
ersi
ty
Cycle number20 25 30 35
Flu
ore
sce
nce
t1
r1
t2
r2
MicrosatelliteGenotyping
Na
/K A
TP
ase
e
xpre
ssio
n
Salinity
Population growth rate
Time
Nu
mb
ers
Salinity
Nt = N0•et
Temperature
morphology
Fst
Qst
Fst (dispersal)
Measures of the extent of divergence between populations relative to the total diversity within all populations
Based on neutral markers (e.g. microsatellites)Provides an indication of geneflow/dispersal between
populations
HT = heterozygosity in total population
HS = average heterozygosity in subpopulationsT
STst H
HHF
)( )(2
)(2
)(2
wpbp
bp
stQ
σ2
p(b) = phenotypic variancebetween populations
σ2p(w) = average phenotypic
variance within populations
Qst (adaptive divergence)
Measures of the extent of divergence between populations relative to the total diversity within all populations
Based on phenotypic traits (e.g. ecophysiological responses, morphometrics)
Provides an indication of adaptive divergence
1)( )(
2)(
2
)(2
)(2
)(2
wpbp
bp
st
wpbp
Q
0)( )(
2)(
2
)(2
)(2
)(2
wpbp
bp
st
wpbp
Q
Qst
)( )(2
)(2
)(2
wpbp
bp
stQ
σ2
p(b) = phenotypic variancebetween populations
σ2p(w) = average phenotypic
variance within populations
Salinity
Salinity
Fst – Qst: comparisonNo dispersal barriers Fst↓Identical environments Qst ↓
Fst
Qst
(popns connected, no adaptive divergence)
0 1
(popns different, no adaptive divergence)Balancing selection
Complete dispersal barrier Fst ↑Identical environments Qst ↓ Fst
Qst0 1
No dispersal barriers Fst↓Different environments Qst ↑
Salinity
Fst
Qst
(popns connected, adaptive divergence)Spatially varying selection
Salinity
Fst – Qst: comparison
0 1
Complete dispersal barrier Fst ↑Different environments Qst ↑
(popns different, adaptive divergence)
Fst
Qst0 1
Gene expression
Gen
etic
an
d p
hen
oty
pic
div
ersi
ty
Cycle number20 25 30 35
Flu
ore
sce
nce
t1
r1
t2
r2
MicrosatelliteGenotyping
Na
/K A
TP
ase
e
xpre
ssio
n
Salinity
Population growth rate
Time
Nu
mb
ers
Salinity
Nt = N0•et
Temperature
morphology
Fst
Qst
So, all we need to do is:
1.Collect many O. marina
2.Make measurements on neutral markers and phenotypic traits
3.Compare Fst-Qst
4.Apply data to landscapes and boundaries
5.Test hypothesis that everything is everywhere and nature selects
But it’s expensive to travel all over the place and would make a big carbon footprint
Solution: we need your help to collect O. marina
Oxyrrhis marina and the marine environment