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186 PAUL J. MARKWICK

Table 2. Spearman rank test rho values for environmental variables and taxonomic species diversity for each

group: all regions

n

Absolute latitude

Elevation

MAT

MART

CMM

WMM

Radiation

Cumulative T 0

Cumulative T 5

Annual precipitation

P range

Months T 10 P 40

PET

Mean annual NDVI

NDVI 1SD

Amphibians

400

-0.576

0,256

0.503

NS

0,396

0.515

NS

0.509

0.531

0.484

0.227

0.670

0.485

0.694

-0.450

Reptiles

411

-0.956

0.268

0.892

-0.358

0.768

0.879

0.825

0.903

0.926

NS

0,231

0.402

0.895

0.598

-0.882

Herptiles

411

-0.931

0.259

0.863

-0.339

0.739

0.852

0.741

0.873

0.893

NS

0.230

0.462

0.869

0.638

-0.851

Mammals

524

-0.462

0.406

0.363

NS

0.275

0.388

0.445

0.380

0.410

0.327

0,377

0.475

0.327

0.562

-0.398

Non-bat

mammals

524

-0.355

0.448

0.219

NS

NS

0.294

0.450

0.244

0.281

0.253

0.285

0.388

0.180

0.472

-0.288

Non-avian

tetrapods

400

-0.869

0.362

0.754

NS

0.591

0.803

0.733

0.824

0.803

NS

0.193

0.450

0.765

0.628

-0.768

(p < 0.0001; NS, not significant, p > 0.0001)

Table 3. Spearman rank test rho values for environmental variables and non-avian tetrapod species diversity by

region

n

Absolute latitude

Elevation

MAT

MART

CMM

WMM

Radiation

Cumulative T 0

Cumulative T 5

Annual precipitation

P range

Months T 10 P 40

PET

Mean annual NDVI

NDVI 1SD

South

America

_

_

_

_

_

_

_

_

_

_

_

__

___

North

America

144

-0.919

0.345

0.891

-0.451

0.805

0.899

NS

0.906

0.910

0.376

NS

0.688

0.895

0.780

-0.858

Europe

204

-0.688

0.478

0,484

NS

NS

0.639

NS

0.504

0.586

NS

NS

0.462

0.539

0.662

-0.622

Arabia

_

_

• 
  
  
  
  • _
    _
    
  
  
  
  


• 
  

  __

  
  


• 
  

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Southern

Africa

12

NS

NS

NS

NS

NS

NS

NS

NS

NS

NS

NS

NS

NS

NS

NS

Australia

40

-0.617

NS

NS

NS

NS

NS

NS

NS

NS

NS

NS

NS

NS

NS

NS

(p < 0.0001; NS, not significant, p > 0.0001)

pattern is consistent with their dependence on
both available water and energy (as tempera-
ture). Such dependence is reflected in the
highest correlations in Table 2 being with combi-
nations of temperature and precipitation
(compare with Fig. 4g). Negative difference
vegetation index; (NDVI, Fig. 4i,j) is a satellite-
derived proxy for net primary productivity
(Goward et al 1985; Goward & Dye 1987; Cihlar
et al 1991), which Lottes & Ziegler (1994) have

shown closely correlates with the number of

months with mean temperatures greater than

10°C and mean precipitation greater than 40 mm

(as a proxy for effective 'growing season'). If this

is the case, then plants, which also depend on

incident energy and water, should show a similar

diversity pattern to amphibians, and this is what

is observed (at least for tree species; Fig. 8).

O'Brien (1993) has shown that climate provides

the first-order explanation for plant species