calc_interaction_intensity2: Calculates the interaction intensity of a food web using...

In lsaravia/EcoNetwork: Ecological network analyses including multiplex networks

Calculates the interaction intensity of a food web using allometric scaling relationships to approximate basal metabolic rate

Description

The function uses the body mass of predator/consumer and the number of prey/resources as source data, then the interaction intensity is estimated based on O'Gorman (2010) as a_ij = -b*(M_jˆ0.25 / s_j), where M_j is the body mass of predator j, s_j is the number of preys, b is a free parameter assumed 0.01. This value of the interaction strength quantifies the effect of the predator on the prey per unit of biomass. Assuming a Lotka-Volterra model is equivalent to the entry A(i,j) of the community matrix, where i is the prey and j the predator. To predict the direct effect of each prey on its predator, a_ji, we could assume an ecological efficiency, e=0.1, reflecting a 10% transfer of energy between trophic levels, hence a_ji = e * a_ij

Usage

calc_interaction_intensity2(
  edge_list,
  consumer_n,
  resource_n,
  bodymass_n,
  b = 0.01,
  e = 0.1,
  output_format = "edgelist"
)

Arguments

edge_list	A tibble containing three columns: consumer, resource, and body mass.
consumer_n	The column name for consumers (predators).
resource_n	The column name for resources (prey).
bodymass_n	The column name for body mass of the consumer.
b	Free parameter (default 0.01).
output_format	Output type: "edgelist" (default, containing only predator effects) or "matrix" (full adjacency matrix).

Details

The function provides two output formats: an edge list with only the effect of predators on prey or an adjacency matrix as a positive number.

Value

A tibble (if output_format = "edgelist") with interaction strengths only for predators on prey on a column named qRC. If output_format = "matrix", an adjacency matrix with interaction strengths. If output_format = "igraph" , an igraph object where edge weights represent predator effects on prey. Always the IS is a positive number.

References

O’Gorman, E. J., Jacob, U., Jonsson, T., & Emmerson, M. C. (2010). Interaction strength, food web topology and the relative importance of species in food webs. Journal of Animal Ecology, 79(3), 682–692. https://doi.org/10.1111/j.1365-2656.2009.01658.x

Examples

library(tibble)

# Define an edge list (consumer, resource, bodymass)
edge_list <- tibble(
  predator = c("A", "A", "B", "C"),
  prey = c("B", "C", "D", "D"),
  predator_mass = c(10, 10, 5, 3)  # Body mass for consumers
)

# Compute interaction strength as an edge list (predator effects only)
interaction_strength_edgelist <- calc_interaction_intensity2(
  edge_list, consumer_n = predator, resource_n = prey, bodymass_n = predator_mass, output_format = "edgelist"
)
print(interaction_strength_edgelist)

# Compute interaction strength as an adjacency matrix
interaction_strength_matrix <- calc_interaction_intensity2(
  edge_list, predator, prey, predator_mass, output_format = "matrix"
)
print(interaction_strength_matrix)

lsaravia/EcoNetwork documentation built on April 5, 2025, 1:51 p.m.