Table 2. Results of best fit generalized least squares models relating β diversity and latitudinal turnover gradient (LTG) strength to mean annual precipitation from paleosols (Retallack, 2007), δ18O (‰) from benthic forams (mm/year; Zachos et al. 2001; 2008), length of North American Land Mammal Age subdivision, number of taxa sampled, sampling area (km2), and number of fossil localities.
| Dependent Variable | Parameters of BestFit Model | Variance explainedby model (%) | t value | p |
| Beta Diversity | Mean annual precipitation (quadratic) | 66.51 | −3.25 | 0.005 |
| Length of NALMA subdivision | 2.43 | 0.027 | ||
| Number of taxa | 5.30 | <0.001 | ||
| Beta Diversity Residuals | Mean annual precipitation (quadratic) | 26.48 | −3.50 | 0.002 |
| Beta Diversity Re-sampled | Mean annual precipitation (quadratic) | 66.04 | −2.39 | 0.029 |
| Length of NALMA subdivision | 2.51 | 0.023 | ||
| Number of taxa | 5.47 | <0.001 | ||
| Latitudinal Turnover Gradient Strength (LTGs) | Mean annual precipitation (quadratic) | 46.76 | −5.65 | <0.001 |
| Area | −4.62 | <0.001 | ||
| Number of taxa | −4.36 | <0.001 | ||
| Area : Number of taxa | 4.85 | <0.001 | ||
| LTG Residuals | Mean annual precipitation (linear) | 37.48 | −3.79 | 0.001 |
| LTG Re-sampled | Number of taxa | 28.59 | −2.55 | 0.020 |