Micro-habitat niche differentiation contributing to coexistence of Eucryptorrhynchus scrobiculatus Motschulsky and Eucryptorrhynchus brandti (Harold).
Temporal, spatial, and trophic niche differentiation usually occurs among species living in similar habitats which can reduce interspecific competition under limited resources. Eucryptorrhynchus scrobiculatus and Eucryptorrhynchus brandti are sympatric and closely related species and are host-specific to Ailanthus altissima (Mill.) Swingle in China. However, the possibility of niche differentiation between the two species is not clear. Therefore, we investigated the density of the two weevils temporally, spatially, and trophically (plant parts of A. altissima) at Lingwu farm and Haojiaqiao town, Lingwu city, Ningxia Hui Autonomous Region. No differences were found in temporal Levin's niche breath index values ranging from 3.74 to 3.95 and temporal Pianka's niche overlap values (0.98-0.99). There was little differentiation in the vertical spatial niche. The vertical distribution of E. scrobiculatus was mainly located from 0 cm (ground) to over 250 cm on tree-of-heaven. Eucryptorrhynchus brandti was found predominantly from 0.1 to 50 cm to over 250 cm on tree-of-heaven. The overlap of the cardinal direction spatial niche was 0.90-0.98, indicating no significant overlap in the cardinal direction at Lingwu farm and Haojiaqiao town. Significant differentiation of trophic niche occurred with E. scrobiculatus feeding on 1-year-old branches, perennial branches, and petioles, while E. brandti feed on the stem.