Table 1.

Proportion of endangered species in other groups that are included in complementary county sets containing all the species in a given group. The second row gives the number of counties in the complementary set for each group; the third row gives the total area of these counties as a percentage of the U.S. land mass. The next eight rows give the total proportion of all other endangered species contained in the complementary set for any given group (columns). Power is an index of how well each species group indicates endangered species diversity in other groups; it is calculated by dividing the number of endangered species from other groups in this complementary county set by the number of such species in an equivalent area of randomly selected counties. A bootstrapping algorithm accumulated counties at random until their total area matched or just exceeded that of the complementary county set. For powera, the algorithm selected from all U.S. counties. For powerb, the algorithm selected only from counties listed as containing endangered species. Because the area encompassed by the random county sets typically was greater than that of the complementary county sets, power underestimates the efficiency of each species group as an indicator for other groups. Power values are means (± SE) of 200 runs of the bootstrapping algorithm.

PlantsMolluscsArthropodsFishHerptilesBirdsMammals
Species (n)5038457107437258
Counties (n)136383757281929
Area (%)9.611.152.384.760.971.592.08
Plants1.000.160.220.150.140.380.27
Molluscs0.391.000.290.440.010.020.06
Arthropods0.540.141.000.160.440.120.19
Fish0.550.150.211.000.090.130.21
Herptiles0.740.210.490.351.000.350.42
Birds0.940.430.470.380.421.000.53
Mammals0.760.380.430.400.330.381.00
All others0.730.210.310.180.250.310.28
Powera1.63 (0.02)2.92 (0.08)2.44 (0.11)1.24 (0.04)3.26 (0.17)4.00 (0.16)2.61 (0.08)
Powerb1.46 (0.01)2.67 (0.06)2.66 (0.59)1.10 (0.02)2.67 (0.06)3.29 (0.09)2.40 (0.08)