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Unformatted text preview: feeding strategy: When are they feeding? Where are they feeding? What are they feeding on? How are they feeding?
All the growth forms combine to form a community of varying physical and/or
Species composition or species diversity The number of species in a community and their relative abundances in that
community Species richness= number of species Equitability/evenness= relative abundances of species in that community (lots of
rare species or lots of species not rare) (higher species diversity) Figure 16.5 Two forest kinds Forest A = 5 species (84% come from one species) Forest B = 5 species (each species represents 20% of total) Same species richness Different evenness, B has higher species evenness (have higher diversity) High species diversity tends to indicate a more complex community With greater variety of species, allowing for a greater array of species interactions Numerous species indices over years
Table 16.1 Shannon index evaluates Species diversity index
Diversity end up H’ = - ￥ p ln p
Take number of species of A and B that’s richness
Number of individuals for each species is equitably (evenness)
Then you take proportion of those individuals of species one out of total
And that number is multiplied by natural log
Takes into account richness and evenness Figure 16.7-8 Rank Abundance Curve 16.17-18 If you take richness and evenness and plot them The more level the slope or line, the greater the species diversity (greater
evenness) within that community Trycopterans- catis flies; in ponds have higher slope; the in the streams they have
shallow slope (greater diversity also Central Gulf have higher species diversity
based on species richness, equitability and slope)
The steeper the curve the less species evenness the greater the species evenness the less
steep the more gradual curve
FACTORS AFFECTING DIVERSITY within communities
o Climatic stability – more stable more diversity (ex: Africa)
o Resource division
o Disturbance – perturbations
o Productivity – how productive is that ecosystem # of species Africa
N. America Lake size Increase in area increases the number if species (species area relationship) Bigger size=more species If you have similar size lakes, you get higher species diversity in African lakes
relative to American because they have greater climatic stability
The African lakes have been around longer speciation increases diversity
CLIMATE STABILITY Bird diversity See Figs. 16.9 and 16.10 Foliage diversity
Resource Division As environmental heterogeneity (complexity of structure or foliage) increases the
number of bird species also increases
Productivity affects diversity
Low foliage height support low bird diversity
What effect does predation have on species diversity?
With this predator Without this predator 15 species of shellfish 8 species of shellfish Robert Paine rocky temperate intertidal coastline in Washington macroinvertebrate
chitons, snails After 5 yrs only 2 spcies remained: 1 gooesnesck Barnacl...
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This document was uploaded on 02/23/2014 for the course CHEM 107 at VCU.
- Spring '12