Table 4. Spatial niche selection indices for D. citri adults in three habitat types in commercial citrus groves in South Texas (2009–2012).
Habitat types are represented by perimeter, adjacent and interior trees.
| Habitat | Proportion of trees available (No. of trees) | Mean No. of D. citri | Selection index W i (Confidence limits) 1 | Standardized selection index (B i) 2 |
|---|---|---|---|---|
| Grapefruit in area-wide surveys (2009–2010) | ||||
| Perimeter | 0.117 (146) | 0.36 | 6.38 (2.71–10.1) a | 0.608 |
| Adjacent | 0.110 (138) | 0.30 | 3.80 (0.26–7.34) ab | 0.358 |
| Interior | 0.773 (966) | 0.13 | 0.22 (0.0–0.49) b | 0.034 |
| χ2 = 34.25, P < 0.0001 | ||||
| Sweet orange in area-wide surveys (2009–2010) | ||||
| Perimeter | 0.104 (156) | 0.48 | 6.58 (3.44–9.71) a | 0.585 |
| Adjacent | 0.097 (148) | 0.30 | 4.19 (1.10–7.30) a | 0.389 |
| Interior | 0.797 (1196) | 0.13 | 0.16 (0.0–0.40) b | 0.026 |
| χ2 = 53.43, P < 0.0001 | ||||
| Young grapefruit grove in field experiments (2012) | ||||
| Perimeter | 0.19 (102) | 9.17 | 4.31 (4.23–4.40) a | 0.893 |
| Adjacent | 0.18 (99) | 3.38 | 0.31 (0.26–0.36) b | 0.064 |
| Interior | 0.63 (341) | 1.77 | 0.21 (0.19–0.23) c | 0.043 |
| χ2 = 158.0, P < 0.0001 | ||||
| Mature grapefruit grove in field experiments (2012) | ||||
| Perimeter | 0.31 (72) | 0.08 | 2.52 (1.95–3.08) a | 0.796 |
| Adjacent | 0.27 (62) | 0.04 | 0.35 (0.0–0.81) b | 0.111 |
| Interior | 0.42 (98) | 0.02 | 0.30 (0.0–0.63) b | 0.094 |
| χ2 = 158.0, P < 0.0001 | ||||
1 W i = selection index of D. citri; Selection indices followed by the same letter are not significantly different at P = 0.05 (log-likelihood ratio [G] test).
2 B i = standardized selection index for D. citri; standardized selection indices of (1/number of habitats), or 0.33 in this case, indicate no preference. Values above 0.33 indicate relative preference, and values below 0.33 indicate relative avoidance.