Principles and examples of distribution and dispersal of patterns microalgae
Mechanisms of origin and
dynamics of (meta-)communities
species-sorting
(niche model)
neutral model
(species equivalent in fittness
and dispersal, extinctions
and speciations matter)
patch dynamics model
(colonization-competitive
trade-offs among species)
mass effects model
(both dispersal and environmental
heterogeneity determine communities)
Leibold et al., 2004,
Ecol. Let. 7
Microalgae (and other protists) typically have much larger
populations that macroorganisms
Unicellular organisms
have large populations.
A population in the glass
has about 225000000
cells.
Thus, protists (incl. microalgae) are typically very small…
What does it mean for their community assembly
and geographic distribution?
This means that in 1 ha pond
there are about 1014 – 1018
individuals of any moderately
abundant species
Marine diatom communities may not be spatially limited but environmentally controlled
Key environmental difference between
N and S hemisphere:
northern ocean is nitrogen limited
southern ocean is iron limited.
Separation of Northern and Southern
communities indicates that environmental
conditions primarily control the global
biogeography of marine diatom
assemblages.
Northern communities are NOT spatially
restricted.
"The lack of dispersal limitation in marine diatoms suggests that the biodiversity at the
microbial level fundamentally differs from that of macroscopic animals and plants for
which geographic isolation is a common component of speciation."
Cermeno & Falkowski., 2009, Science 325: 1539-1541
Reaction of oceanic diatom communities to climate change shows that there are not
any significant limits to dispersal. Conversely, local environmental factors are
important.
Cermeno et al. 2010, PloS One 5
Cermeno et al. 2010, PloS One 5
Priest Pot – a model pool for study of local protistan diversity
R=0.69
abundance of paraphysomonades in 0,1cm2 of
surface sediment from Priest Pot
vs.
global abundance (frequency of reports) of taxa
Finlay & Clarke, 1999, Protist 150:419-430.
Finlay & Clarke, 1999, Nature 400:828.
proportion of cosmopolitan morphospecies
sharply increases in body size groups less
than pod 1 mm
Finlay & Fenchel, 2004, Protist 155:237-244.
„NEUTRAL“ THEORY OF UBIQUITOUS DISTRIBUTION OF EUKARYOTIC MICROORGANISMS
strong formulation:
“everything is everywhere but many species are locally extremely rare”
weak formulation:
“environment selects for local distribution of taxa”
(= zero role of history in protist biogeography due to frequent dispersal)
Finlay, 2002, Science 296:1061-1063.
Community patterns of lake diatoms indicate local adaptation and, therefore, effect of
dispersal limitations on global biogeography
diatom diversity optima strongly correlate
with reagionally most abundant habitats
N Florida, S Norway, Lappland
Should global dispersal be spatially limited, structure of regional communities
must depend on regional habitat availability (= local adaptation of taxa)
Telford et al., 2006, Science 312:1015 .
Global diversity and distribution of benthic lake diatoms indicates spatial dispersal limits
Vyverman et al., 2007, Ecology 88:1924-1931.
Local diversity of lake phytoplankton is best explained by regional, not local,
environmental factors
Local phosphorus (P) concentrations best explain local mean algal biovolumes.
But:
Relation of local P concentrations and diversity is very weak.
About 70% of local diversity is explained by regional P concentrations on scale of 100-400 km.
Ptacnik et al., 2010, Proc Royal Soc Biol 277
Ptacnik et al., 2010, Proc Royal Soc Biol 277
regional species pool
"The frequent claim that dispersal limitation does not affect microbial diversity owing to
their high dispersal rates apparently oversees the equally high extinction rates in
microbial communities. Fast dispersal of micro-organisms may certainly explain the
cosmopolitan distribution of numerous protist morpho-species. However, on the local
level, maintenance of high diversity in microbial communities also depends on having
species-rich habitats within proximate distance."
Ptacnik et al., 2010, Proc Royal Soc Biol 277
Mechanisms of "species-sorting" cannot explain community structure of benthic
stream and river diatoms; spatial effects are important on scale of hundreds of
kilometers
Heino et al. 2010, Oikos 119
strong effect of purely „spatial“
factors, possibly related to
dispersal and isolation of
localities
low effect of individual
environmental factors
Heino et al. 2010, Oikos 119