With species richness studies, ecologists often employ
rank abundance curves, which are graphs ranking the most
abundant species to the least abundant (Adams, 2009).
They can be shown as a plot of number of species vs. the
number of individuals on a logarithmic scale that usually
yields a normal distribution. This is because environments
are usually undersampled, especially in high diversity
systems or regions. Singlets make up the middle
peak of the distribution, and the more sampling that is
conducted, the more the curve will shift to the right. The
number of unsampled species in cases of undersampling
can be roughly estimated using the Chao estimator, in
which S estimate ¼ S observed + F 1
2
/2F 2 where F 1 is the
number of singletons sampled and F 2 is the number of
doublets. There is also a method of estimating what percent of the total species is represented in a sample,
called Good’s coverage estimator, in which Coverage
¼ 1 À (the number of individuals in species/total number
of individuals). These estimator equations allow
researchers to determine how their limited sampling
relates to the entire sampled population (Chao, 2005).
Bibliography
Adams, J., 2009. Species Richness: Patterns in the Diversity of Life.
New York: Springer Praxis Books.
Bower, J. E., and Zar, J. H., 1995. Field and Laboratory Methods
for General Ecology. Dubuque, IA: William C. Brown
Publishers.
Chao, A., 2005. Species richness estimation. In Balakrishnan, N.,
Read, C. B., and Vidakovic, B. (eds.), Encyclopedia of Statistical
Sciences. New York: John Wiley and Sons, pp. 7909–7916.
de Queiroz, K., 2007. Species concept and species delimitation.
Systematic Biology, 56(6), 879–886.
Gotelli, N. J., and Colwell, R. K., 2001. Quantifying biodiversity:
procedures and pitfalls in the measurement and comparison of
species richness. Ecology Letters, 4, 379–391.
Maguran, A. E., 1988. Ecological Diversity and Its Measurement.
Princeton: Princeton University Press.
Smith, R. L., Smith T. M., 2001. Elements of ecology pearson education. In Addison Wesley Longman S. A. (eds.). Inc.
Cross-references
Shannon-Weaver Diversity Index
SPECIES ZONATION
Vic Semeniuk
1 and Ian Cresswell
2
1
V & C Semeniuk Research Group, Warwick, WA,
Australia
2
Land & Water National Research Flagship, CSIRO,
Hobart, TAS, Australia
Definition
Species zonation is the occurrence of species or groups of
species in distinct bands or zones coincident with or
related to environmental gradients.
Introduction
Species zonation is the occurrence of species or groups of
species in distinct bands or zones coincident with or
related to environmental gradients. It is a common feature
observed within estuaries where the distribution and abundance of its biota respond to the combined and interactive
effects of steep environmental gradients and food availability and to interspecies competition, herbivory, and predation (Paine, 1974; Pennings and Callaway, 1992;
Levinton, 1995). The distribution and abundance of individual species (as a result of their tolerances to the combined effects of the environmental gradients) results in
compositional changes in biotic assemblages across these
gradients. For vegetation, species zonation is often manifest as visually distinct vegetation communities; for
rock-inhabiting communities, it is commonly manifest as
visually distinct bands of different encrusting shelly
organisms, epibenthos, and algae. For infauna, it is manifest as compositional and abundance changes in the communities across the habitat as determined by sampling and
mapping. In areas of less steep environmental gradients,
species often occur in less differentiated formations, such
as mottled mosaics or with diffuse zonation.
The description and discussion of species zonation provided here is for a positive estuary that grades from freshwater at the river entrance to marine at the estuary mouth,
but the principles of species response also apply to inverse
estuaries where evaporation from the surface water
exceeds the freshwater runoff entering the estuary.
Variation on zonation in different environmental
situations
In estuaries where there is a strong seasonal to perennial
delivery of freshwater via subterranean seepage from
supratidal environments (Semeniuk, 1983; Cresswell,
2000), the gradient of increasing salinity and pore-water
content upslope can be locally reversed at the contact of
the tidal flat with the supratidal zone. Where frequency
of inundation and concomitant change in wave energy
and tidal current energy also result in a differentiation/
partitioning of sediment grain sizes across the tidal flat
(from sand in low tidal areas to mud in high tidal areas),
there may be three gradients across the tidal flat, that of
salinity, pore-water content, and sediment grain size. As
a consequence, biota responding to these gradients in concert often forms distinct zonation across the flat.
Heterogeneous distribution of habitats and lack of
species zonation
In many estuaries there are mosaics of habitats and
mosaics of biotic assemblages and occurrences of species
relating to these habitats. Due to the particular and determinative environmental conditions present in a habitat,
the species composition of biotic assemblages can vary
markedly between habitats. Estuaries with heterogenous
distribution of habitats can result in a mosaic of biotic
assemblages corresponding to these habitats within the
SPECIES ZONATION
613
rank abundance curves, which are graphs ranking the most
abundant species to the least abundant (Adams, 2009).
They can be shown as a plot of number of species vs. the
number of individuals on a logarithmic scale that usually
yields a normal distribution. This is because environments
are usually undersampled, especially in high diversity
systems or regions. Singlets make up the middle
peak of the distribution, and the more sampling that is
conducted, the more the curve will shift to the right. The
number of unsampled species in cases of undersampling
can be roughly estimated using the Chao estimator, in
which S estimate ¼ S observed + F 1
2
/2F 2 where F 1 is the
number of singletons sampled and F 2 is the number of
doublets. There is also a method of estimating what percent of the total species is represented in a sample,
called Good’s coverage estimator, in which Coverage
¼ 1 À (the number of individuals in species/total number
of individuals). These estimator equations allow
researchers to determine how their limited sampling
relates to the entire sampled population (Chao, 2005).
Bibliography
Adams, J., 2009. Species Richness: Patterns in the Diversity of Life.
New York: Springer Praxis Books.
Bower, J. E., and Zar, J. H., 1995. Field and Laboratory Methods
for General Ecology. Dubuque, IA: William C. Brown
Publishers.
Chao, A., 2005. Species richness estimation. In Balakrishnan, N.,
Read, C. B., and Vidakovic, B. (eds.), Encyclopedia of Statistical
Sciences. New York: John Wiley and Sons, pp. 7909–7916.
de Queiroz, K., 2007. Species concept and species delimitation.
Systematic Biology, 56(6), 879–886.
Gotelli, N. J., and Colwell, R. K., 2001. Quantifying biodiversity:
procedures and pitfalls in the measurement and comparison of
species richness. Ecology Letters, 4, 379–391.
Maguran, A. E., 1988. Ecological Diversity and Its Measurement.
Princeton: Princeton University Press.
Smith, R. L., Smith T. M., 2001. Elements of ecology pearson education. In Addison Wesley Longman S. A. (eds.). Inc.
Cross-references
Shannon-Weaver Diversity Index
SPECIES ZONATION
Vic Semeniuk
1 and Ian Cresswell
2
1
V & C Semeniuk Research Group, Warwick, WA,
Australia
2
Land & Water National Research Flagship, CSIRO,
Hobart, TAS, Australia
Definition
Species zonation is the occurrence of species or groups of
species in distinct bands or zones coincident with or
related to environmental gradients.
Introduction
Species zonation is the occurrence of species or groups of
species in distinct bands or zones coincident with or
related to environmental gradients. It is a common feature
observed within estuaries where the distribution and abundance of its biota respond to the combined and interactive
effects of steep environmental gradients and food availability and to interspecies competition, herbivory, and predation (Paine, 1974; Pennings and Callaway, 1992;
Levinton, 1995). The distribution and abundance of individual species (as a result of their tolerances to the combined effects of the environmental gradients) results in
compositional changes in biotic assemblages across these
gradients. For vegetation, species zonation is often manifest as visually distinct vegetation communities; for
rock-inhabiting communities, it is commonly manifest as
visually distinct bands of different encrusting shelly
organisms, epibenthos, and algae. For infauna, it is manifest as compositional and abundance changes in the communities across the habitat as determined by sampling and
mapping. In areas of less steep environmental gradients,
species often occur in less differentiated formations, such
as mottled mosaics or with diffuse zonation.
The description and discussion of species zonation provided here is for a positive estuary that grades from freshwater at the river entrance to marine at the estuary mouth,
but the principles of species response also apply to inverse
estuaries where evaporation from the surface water
exceeds the freshwater runoff entering the estuary.
Variation on zonation in different environmental
situations
In estuaries where there is a strong seasonal to perennial
delivery of freshwater via subterranean seepage from
supratidal environments (Semeniuk, 1983; Cresswell,
2000), the gradient of increasing salinity and pore-water
content upslope can be locally reversed at the contact of
the tidal flat with the supratidal zone. Where frequency
of inundation and concomitant change in wave energy
and tidal current energy also result in a differentiation/
partitioning of sediment grain sizes across the tidal flat
(from sand in low tidal areas to mud in high tidal areas),
there may be three gradients across the tidal flat, that of
salinity, pore-water content, and sediment grain size. As
a consequence, biota responding to these gradients in concert often forms distinct zonation across the flat.
Heterogeneous distribution of habitats and lack of
species zonation
In many estuaries there are mosaics of habitats and
mosaics of biotic assemblages and occurrences of species
relating to these habitats. Due to the particular and determinative environmental conditions present in a habitat,
the species composition of biotic assemblages can vary
markedly between habitats. Estuaries with heterogenous
distribution of habitats can result in a mosaic of biotic
assemblages corresponding to these habitats within the
SPECIES ZONATION
613