Transcript Druhová diverzita na gradientech prostředí

Theory of island biogeography
(Mac Arthur, Wilson 1963)
• Effect of age, distance and area of
an island on species richness
Generalization [to be seen in
each textbook]
Results in classical species area
relationship for islands (usually
steeper then within a mainland)
Reptiles and amphibians – from Wikipedia
Diversity on gradients
Geography
• Decrease with increasing latitude (will be
discussed by Vojta Novotný)
• Historical causes – glacial periods in
temperate
• Europe –mountain ridges in E-W direction –
barrier for migration – less species
• Physiological limitation – tropical species
are not able to grow in temperate climate
Note the importance of mountains at this spatial scale
Tree species
richness in Canada
and the United
States. Contours
connect points with
the same
approximate
number of species
per quadrat.
Quadrat size is 2.5˚
x 2.5˚ south of
50˚N, and 2.5˚ x 5˚
north of 50˚N
(Currie and Paquin
1987).
Medium disturbance hypothesis – is reflected in
successional gradients
Changes in species
richness during an
old-field succession,
measured on various
spatial scales. The
numbers on the right
side are sizes of
sampling plots
expressed as the
lengths of the
quadrat side. From
Osbornová et al.
1990.
DIVERSITY ON
PRODUCTIVITY GRADIENTS
Generality of unimodal (humpedback) model? – Problems with scale and
extend
Examples of unimodal
relationships between species
richness and measures of habitat
productivity in plant
communities. P* and K* are
normalised concentrations of soil
phosphorus and potassium,
which were summed to give an
index of soil fertility. From
Tilman and Pacala (1993), where
also the references to original
source can be found.
Fraser et al. Worldwide evidence of a unimodal relationship
between productivity and plant species richness. - SCIENCE · JULY
2015 - but richness depends on productivity!!!!! – X, Y axis
Skácelová &
Lepš, 2014,
Hydrobiologia
Phytoplankton
diversity
Relationship between log
(biovolume [lm3/ml]) and
indices of Hill’s series:
N0, the number of
species, N1, antilog of
Shannon diversity, eH,
N2, reciprocal of Simpson
index of
dominance, and N?,
reciprocal of Berger–
Parker index of
dominance, fitted by
GAM.
In benign environment, diversity decreases with productivity – why?
1
Control fertilised
Removal fertilised
Removal non-fertilised
Species proportion
0.1
0.01
Control non-fertilised
0.001
0.0001
0.00001
Species sequence
Mown wet meadows under fertilization and dominant removal
Why the number of species
decreases with productivity?
• 1. Species pool hypothesis – there have
been not many habitats with such a high
productivity (at least grasslands)
• But – most mesotrophic species are able to
grow in productive habitats – so the
evolutionary adaptatioh here must include
also adaptation to biotic interactions
Why the number of species
decreases with productivity?
• 2. Biotic interactions (competition) within
the community
Is competition higher in more
productive environment?
• Tilman: no, it is only change from
underground to aboveground competition
• Grime: Yes, competition increases in fertile
environment.
• Each of them defines and measures
competition in different way
“Tilmanian” explanation
• Rate of competitive exclusion depends not
only on intensity,but also on competition
asymmetry. In productive environment,
competition for light, which is more
asymmetric, prevails, and so the faster
competitive exclusion.
Ohrazeni experiment – best predictor for
success under fertilization is plant height
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Respontferilzaton
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“Grimean” explanation
• With increasing productivity, the rate of all
processes and intensity of competition
increases.