Niche Overlap Index Function
Niche overlap refers to the extent to which different species use the same resources or occupy similar ecological niches. High niche overlap might indicate intense competition, whereas low overlap suggests niche differentiation, allowing species to coexist by minimizing direct competition.
Functionality Overview
To capture the changes in density-independent abiotic response, also known as niche breadth, this implementation developed based on Pianka's Niche Overlap Index, as suggested by Pianka (1973). The summary statistics of this index include the mean, maximum, and minimum values across all species pairs, providing a comprehensive understanding of niche sharing within the community.
Since most ecological datasets lack direct measurements of species-specific resource utilization, we developed an adaptation of the original niche overlap index that can be applied to abundance data. Specifically, our implementation assumes all species share the same consumption rate and type I functional response, such that species with higher abundance have proportionally higher resource utilization at any given site-time combination. This assumption allows abundance data to serve as a proxy for resource utilization patterns, enabling calculation of niche overlap index from observed abundance data. Keep in mind that this approach will not be able to reflect the fact that some species may be more efficient in consumption than others. Therefore, this approach works best when comparing species with similar body sizes, metabolic rates, or feeding strategies, as these factors strongly influence the abundance-consumption relationship.
The Function
MetaCommunityMetrics.niche_overlap — Functionniche_overlap(abundance::AbstractVector, species::AbstractVector, site::AbstractVector, time::AbstractVector) -> DataFrameCalculates the overall mean, maximum, and minimum values of the niche overlap index from all species pairs in the provided data.
Arguments
abundance::AbstractVector: Vector representing the abundance of species.species::AbstractVector: Vector representing species names or IDs.site::AbstractVector: Vector representing site names or IDs.time::AbstractVector: Vector representing sampling dates.
Description
The niche overlap index is calculated based on the method suggested by Pianka (1973), with the assumption that the proportional use of resources by a species at a specific site and time is equivalent to its relative abundance at that location and time period across all sampled sites and times.
Returns
DataFrame: A DataFrame containing the overall mean, maximum, and minimum values of the niche overlap index from all species pairs.
Example
julia> using MetaCommunityMetrics
julia> df = load_sample_data()
53352×12 DataFrame
Row │ Year Month Day Sampling_date_order plot Species Abundance Presence Latitude Longitude standardized_temperature standardized_precipitation
│ Int64 Int64 Int64 Int64 Int64 String3 Int64 Int64 Float64 Float64 Float64 Float64
───────┼──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
1 │ 2010 1 16 1 1 BA 0 0 35.0 -110.0 0.829467 -1.4024
2 │ 2010 1 16 1 2 BA 0 0 35.0 -109.5 -1.12294 -0.0519895
3 │ 2010 1 16 1 4 BA 0 0 35.0 -108.5 -0.409808 -0.803663
4 │ 2010 1 16 1 8 BA 0 0 35.5 -109.5 -1.35913 -0.646369
5 │ 2010 1 16 1 9 BA 0 0 35.5 -109.0 0.0822 1.09485
⋮ │ ⋮ ⋮ ⋮ ⋮ ⋮ ⋮ ⋮ ⋮ ⋮ ⋮ ⋮ ⋮
53348 │ 2023 3 21 117 9 SH 0 0 35.5 -109.0 -0.571565 -0.836345
53349 │ 2023 3 21 117 10 SH 0 0 35.5 -108.5 -2.33729 -0.398522
53350 │ 2023 3 21 117 12 SH 1 1 35.5 -107.5 0.547169 1.03257
53351 │ 2023 3 21 117 16 SH 0 0 36.0 -108.5 -0.815015 0.95971
53352 │ 2023 3 21 117 23 SH 0 0 36.5 -108.0 0.48949 -1.59416
53342 rows omitted
julia> result = niche_overlap(df.Abundance, df.Species, df.plot, df.Sampling_date_order)
1×3 DataFrame
Row │ mean_niche_overlap_index min_niche_overlap_index max_niche_overlap_index
│ Float64 Float64 Float64
─────┼────────────────────────────────────────────────────────────────────────────
1 │ 0.0923816 0.0 0.406837References
- MacArthur, R., & Levins, R. (1967). The limiting similarity, convergence, and divergence of coexisting species. The american naturalist, 101(921), 377-385. https://doi.org/10.1086/282505
- Pianka, E. R. (1974). Niche overlap and diffuse competition. Proceedings of the National Academy of Sciences, 71(5), 2141-2145. https://doi.org/10.1073/pnas.71.5.2141
- Pianka, E. R. (1973). The structure of lizard communities. Annual review of ecology and systematics, 53-74. https://www.jstor.org/stable/2096804