Omnivory {cheddar} | R Documentation |
Omnivory
Description
Nodes that consume two or more species and have a non-integer trophic level.
Usage
IsOmnivore(community, level=PreyAveragedTrophicLevel)
Omnivores(community, ...)
FractionOmnivorous(community, ...)
Omnivory(community, ...)
Arguments
community |
an object of class |
level |
a function that returns the trophic level of each node in
|
... |
other values to |
Details
Omnivores are those nodes that consume two or more species and have a
non-integer trophic level (Polis 1991). IsOmnivore
returns a vector of
logical
of length NumberOfNodes
; values are TRUE
for
nodes that are omnivorous. Omnivores
returns the names of nodes for
which IsOmnivore
returns TRUE
. FractionOmnivorous
and
Omnivory
both return the proportion of nodes for which IsOmnivore
returns TRUE
.
Many researchers have used chain-averaged trophic level when computing omnivory
(Polis, 1991; Bersier et al 2002). Computing chain-averaged trophic level
requires enumerating every unique food chain - this can be lengthy for complex
food webs so the default function used by IsOmnivore
is
PreyAveragedTrophicLevel
. Omnivory values obtained using these two
methods might differ slightly.
Value
Either a logical
vector of length NumberOfNodes
or a
vector of names.
Author(s)
Lawrence Hudson
References
Polis, G. A. (1991) Complex desert food webs: an empirical critique
of food web theory. American Naturalist 138
, 123–155.
Bersier, L. and Banasek-Richter, C. and Cattin, M. (2002) Ecology 80 2394–2407.
See Also
NumberOfNodes
, PreyAveragedTrophicLevel
,
ChainAveragedTrophicLevel
Examples
data(TL84)
IsOmnivore(TL84)
Omnivores(TL84)
Omnivory(TL84)
# Omnivory values found using PreyAveragedTrophicLevel and
# ChainAveragedTrophicLevel differ for ChesapeakeBay
data(ChesapeakeBay)
Omnivory(ChesapeakeBay)
Omnivory(ChesapeakeBay, level=ChainAveragedTrophicLevel)