compare_E: Compare E between species or populations using permutation

Description

To test whether or not distinct species or populations (hereafter 'entity') differed in their effectiveness of thermoregulation, Hertz et al. (1993) suggested comparing paired estimates of E obtained through bootstrapping. However, because sample sizes of active body temperatures (Tb) or operative temperatures (Te) may be small and could differ in size and variance, possibly leading to non-normality, we propose to use two-sided permutation testing instead of bootstrapping to build and compare distributions of E values.

Usage

compare_E(
  datasp1,
  datasp2,
  tset_lowsp1,
  tset_upsp1,
  tset_lowsp2,
  tset_upsp2,
  index,
  n
)

Arguments

datasp1

A dataframe with two columns named 'te' (containing operative temperatures) and 'tb' (containing body temperature measurements) of entity 1. Do not use capitals in column names.

datasp2

A dataframe for entity 2 structured as indicated above.

tset_lowsp1

Lower boundary of the set-point range of entity 1 that was determined through thermal preference trials in a temperature gradient. This may be a named double vector containing the lower boundary value, or simply the value itself.

tset_upsp1

Upper boundary of the set-point range of entity 1.

tset_lowsp2

Lower boundary of the set-point range of entity 2.

tset_upsp2

Upper boundary of the set-point range of entity 2.

index

Either 'hertz' or 'blouin'.

The desired number of samples drawn without replacement.

Value

Permutation testing results including a graphical overview which displays the empirical (actual) difference in E between two entities, along with a null distribution of differences in permuted E values constructed from pooled data of both entities.

References

Blouin-Demers, G., & Weatherhead, P. J. (2001). Thermal ecology of black rat snakes (Elaphe obsoleta) in a thermally challenging environment. Ecology, 82 (11), 3025-3043. Hertz, P. E., Huey, R. B., & Stevenson, R. D. (1993). Evaluating temperature regulation by field-active ectotherms: the fallacy of the inappropriate question. The American Naturalist, 142(5), 796-818.

Examples

Run this code

# NOT RUN {
bufbuf <- bufbuf
ichalp <- ichalp
E_diff <- compare_E(bufbuf, ichalp,
                    19.35, 26.44,
                    14.44, 18.33,
                    'blouin',
                    1000)

# }