The Self-Similarity Curve: a New Method of Determining the Sampling Effort Required to Characterize Communities

Streever, William; Bloom, SA

doi:10.1080/02705060.1993.9664879

“…When patches of P. cordata were interspersed with other plants or open water, samples were intentionally collected from within the patches of P. cordata. A priori power analysis of pilot data (Streever and Portier 1994) and an estimate of the number of samples required to adequately represent individual wetlands (Streever and Bloom 1993. ) dictated the number of samples.…”

Section: Field Methodsmentioning

confidence: 99%

A comparison of dipterans from ten created and ten natural wetlands

Streever

¹

,

Portier

²

,

Crisman

³

1996

View full text Add to dashboard Cite

This study compares densities of common larval dipterans collected from areas dominated by Pontederia cordata in t0 natural and 10 created freshwater herbaceous wetlands in central Florida. At each wetland, 7 core samples were collected from each of 5 stations during summer 1993. In addition, stem densities, vegetation areal coverage, pH, dissolved oxygen, water temperature, water depth, conductivity, sediment quality, and leaf litter were measured at 3 locations near each of the 5 stations in each wetland. Of the 57 dipteran taxa collected, 20 occurred with sufficient abundance to justify statistical comparison. Despite a large sampling effort, there were no significant differences in densilies of 20 commonly occurring taxa found in created and natural wetlands after considering the effect of multiple univariate tests. Comparison of environmental variables showed significant differences in stem densities for vegetation other than P, cordata, pH, conductivity, and sediment quality. Canonical correspondence analysis, used to relate environmental and biological variables, suggests that pH, conductivity, and sediment quality are only weakly related to dipteran community structure. Despite differences in environmental conditions, there is no convincing evidence of differences in natural and created wetland dipteran communities.

show abstract

“…Although, in a statistical sense, randomization in the repeated selection of sample units provides assurance that samples represent the target community, randomization alone does not provide a basis for determining how similar the sample is to the community from which it is drawn. Streever and Bloom (1993) used the term self-similarity for the similarity among replicate samples, but the term has been widely adopted in fractal geometry for a different purpose (Palmer 1988, Kenkel and Walker 1996, Harte et al 1999. Using similarity as a criterion for guiding sampling effort is fundamentally different from sampling to achieve a given level of precision, a topic that has been well addressed (e.g., Green 1979, Sokal and Rohlf 1981, Norris and Georges 1986, Manly 1992.…”

Section: Introductionmentioning

confidence: 99%

Comparison of Ecological Communities: The Problem of Sample Representativeness

Cao

¹

,

Williams

²

,

Larsen

³

2002

Ecological Monographs

View full text Add to dashboard Cite

Obtaining an adequate, representative sample of ecological communities to make taxon richness (TR) or compositional comparisons among sites is a continuing challenge. Although randomization in the collection of sample units is often used to assure that sampling is representative, randomization does not convey the concept of how well samples represent the community or site from which they are drawn. In ecological surveys, how well a sample represents a community or site literally means the similarity in taxon composition and relative abundance between a sample and the community from which it is drawn. Using both field and simulated data, we show that the proportion of the total taxon richness at a site (%TTR) achieved with a fixed sample size varies across sites, which in turn causes changes in site-to-site differences in observed TR with sample size. This means that equal-sized samples may differentially represent the communities from which they are drawn. However, the similarity of a sample to the community from which it is drawn cannot be measured directly because the taxon composition and relative abundance of the community is usually unknown. We propose to estimate it by measuring the average similarity among replicate samples randomly drawn from a community, i.e., autosimilarity, which is measured with Jaccard Coefficient in this study. Using the same data sets, we found that:(1) samples of equal size from different sites or communities achieved different levels of autosimilarity, with lower levels achieved in taxon richer sites, indicating variation in how well samples of equal size represent their respective communities; (2) %TTR was positively and almost linearly correlated with autosimilarity, indicating that autosimilarity might be a good predictor of TTR; and (3) when samples were compared at the same level of autosimilarity, similar %TTRs across different sites were achieved (i.e., the relative differences in taxon richness among sites became independent of sample size). We conclude that standardization on autosimilarity, rather than on sample size, can improve the accuracy of taxon richness comparisons.

show abstract

“…In contrast, if replicate samples are highly different from one another (i.e., average similarity is close to zero), the sample poorly represents the community. Streever and Bloom (1993) used the term self-similarity for the similarity among replicate samples, but the term has been widely adopted in fractal geometry for a different purpose (Palmer 1988, Kenkel and Walker 1996, Harte et al 1999. To avoid confusion, we use autosimilarity to stand for average similarity among replicate samples.…”

Section: Introductionmentioning

confidence: 99%

Comparison of Ecological Communities: The Problem of Sample Representativeness

Cao¹,

Williams²,

Larsen³

2002

Ecological Monographs

View full text Add to dashboard Cite

Obtaining an adequate, representative sample of ecological communities to make taxon richness (TR) or compositional comparisons among sites is a continuing challenge. Although randomization in the collection of sample units is often used to assure that sampling is representative, randomization does not convey the concept of how well samples represent the community or site from which they are drawn. In ecological surveys, how well a sample represents a community or site literally means the similarity in taxon composition and relative abundance between a sample and the community from which it is drawn. Using both field and simulated data, we show that the proportion of the total taxon richness at a site (%TTR) achieved with a fixed sample size varies across sites, which in turn causes changes in site-to-site differences in observed TR with sample size. This means that equal-sized samples may differentially represent the communities from which they are drawn. However, the similarity of a sample to the community from which it is drawn cannot be measured directly because the taxon composition and relative abundance of the community is usually unknown. We propose to estimate it by measuring the average similarity among replicate samples randomly drawn from a community, i.e., autosimilarity, which is measured with Jaccard Coefficient in this study. Using the same data sets, we found that:(1) samples of equal size from different sites or communities achieved different levels of autosimilarity, with lower levels achieved in taxon richer sites, indicating variation in how well samples of equal size represent their respective communities; (2) %TTR was positively and almost linearly correlated with autosimilarity, indicating that autosimilarity might be a good predictor of TTR; and (3) when samples were compared at the same level of autosimilarity, similar %TTRs across different sites were achieved (i.e., the relative differences in taxon richness among sites became independent of sample size). We conclude that standardization on autosimilarity, rather than on sample size, can improve the accuracy of taxon richness comparisons.

show abstract

The Self-Similarity Curve: a New Method of Determining the Sampling Effort Required to Characterize Communities

Cited by 6 publications

References 2 publications

A comparison of dipterans from ten created and ten natural wetlands

A comparison of dipterans from ten created and ten natural wetlands

Comparison of Ecological Communities: The Problem of Sample Representativeness

Comparison of Ecological Communities: The Problem of Sample Representativeness

Contact Info

Product

Resources

About