bipartite (version 2.19)

nestedcontribution: Calculates the per-species contribution to nestedness (z-score relative to null model)

Description

Estimates the degree to which the interactions of each row and column species increase or decrease community nestedness.

Usage

nestedcontribution(web, nsimul = 99)

Value

For both the “higher trophic level” and the “lower trophic level”, this function returns a data frame with the per-species nestedness contributions.

Arguments

web

A matrix with elements of a set (e.g., plants) as rows, elements of a second set (e.g., pollinators) as columns and number of interactions as entries. Non-binary matrices will be converted to 0/1 data.

nsimul

Number of randomizations to use as the basis for each comparison.

Author

Daniel B. Stouffer

Details

The idea behind nestedness contribution is to determine how individual species' interactions change community nestedness compared to a random null model that is designed to control for the effect of differences in degree. For each row and column species, this function compares observed nestedness to an ensemble of nestedness values generated by randomizing the interactions of just that focal species. Nestedness contributions are the z-scores from this comparison. Therefore, a positive contributor to community nestedness (i.e., a species whose interactions increase overall nestedness) will obtain values greater than 0 and negative contributors to nestedness will obtain values less than 0.

References

Bascompte, J., Jordano, P., Melián, C.J., and Olesen, J.M. 2003. The nested assembly of plant-animal mutualistic networks. Proceedings of the National Academy of Sciences of the USA 100, 9383--9387

Saavedra, S., Stouffer, D.B., Uzzi, B., and Bascompte, J. 2011. Strong contributors to network persistence are the most vulnerable to extinction. Nature 478, 233--235

Examples

  data(Safariland)
  if (FALSE) {
    nestedcontribution(Safariland)
  }