Table 2.
Minimum adequate models of the relationship between avian species richness and (a) proportion of protected land and (b) presence/absence of protected land, while taking plot area and environmental energy (NDVI) into account. (The negative species–area relationship is driven by high species-richness in the smallest 3% of grid-cells and does not occur when these are excluded from analyses. For further details, see table 1. Positive effects: +++p<0.001, ++++p<0.0001; negative effects: −−p<0.01, −−−−p<0.0001; factors: *p<0.05, **p<0.01, ****p<0.0001; n.s., not significant.)
| change in fit cf. to model without prop. protected land | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| (a) response | cells with no protected area included? | model type | prop. protected land | January NDVI | prop. protected land×January NDVI | grid cell area | model fit | interaction term (%) | prop. protected land (and interaction term, where significant) |
| total richness | yes | GLM | F1,1250=66.1++++ | F1,1250=523.7++++ | F1,1250=11.1+++ | r2=52.6% | partial r2=0.4 | partial r2=9.4% | |
| spatial | F1,1250=87.9++++ | F1,1250=109.4++++ | F1,1250=8.2−− | AIC=4369.7 | ΔAIC=−78.7 | ||||
| no | GLM | F1,515=21.0++++ | F1,515=369.6++++ | r2=42.5% | partial r2=2.3% | ||||
| spatial | F1,515=28.9++++ | F1,515=76.5++++ | AIC=1842.8 | ΔAIC=−24.7 | |||||
| threat. richness | yes | GLM | F1,1249=69.6++++ | F1,1249=416.8++++ | F1,1249=28.0++++ | F1,1249=34.6−−−− | r2=41.4% | partial r2=1.3 | partial r2=6.2% |
| spatial | F1,1250=58.7++++ | F1,1250=127.3++++ | F1,1250=22.1−− | AIC=2689.0 | ΔAIC=−49.6 | ||||
| no | GLM | F1,514=35.1++++ | F1,514=260.5++++ | F1,514=16.4−−−− | r2=36.3% | partial r2=4.3% | |||
| spatial | F1,514=31.7++++ | F1,514=64.2++++ | F1,514=8.6−− | AIC=11 625 | ΔAIC=−26.4 | ||||
| change in fit cf. to model without pres/abs protected land | ||||||||
|---|---|---|---|---|---|---|---|---|
| (b) response | model type | presence/absence of protected land | January NDVI | presence/absence protected land×January NDVI | grid cell area | model fit | interaction term | pres/abs protected land (and interaction term, where significant) |
| total richness | GLM | F1,1250=52.9**** | F1,1250=762.4++++ | F1,1250=7.4** | r2=51.7 | partial r2=0.3% | partial r2=8.5% | |
| spatial | F1,1249=0.5 n.s. | F1,1249=105.8++++ | F1,1249=4.0* | F1,1249=10.1−− | AIC=4382.2 | ΔAIC=−4.4 | ΔAIC=−66.2 | |
| threat. richness | GLM | F1,1249=55.7**** | F1,1249=555.5++++ | F1,1249=23.9**** | F1,1249=38.4−−−− | r2=40.0% | partial r2=1.1% | partial r2=4.8% |
| spatial | F1,1250=37.8**** | F1,1250=129.8++++ | F1,1250=25.0−−−− | AIC=2706 | ΔAIC=−32.6 | |||