Scale-dependent contribution of host-specificity and environmental factors to wood-boring longhorn beetle community assemblage in SW China

Abstract

Longhorn beetles are extremely rich wood-boring insects possessing larvae that feed on the xylem of trees and/or lianas, which have detrimental effects on plants; in turn, the hosting plants may play a fundamental role in shaping the longhorn beetle community assemblage. However, factors determining the community assemblage of wood-boring longhorn beetles, particularly along the multiple spatial scales is still in need of further exploration. In this study, we designed an experiment across several spatial scales (from local to macro scales) from tropical to temperate climate gradients in Yunnan province, southwest China to examine to what extend the attributes of host-specificity is shaping the community assemblage along different spatial scales. This study concludes that (1) the wood-boring longhorn beetles showed attributes of host-specificity to a certain degree at the community level, (2) biotic (host plant specificity) and abiotic (climatic gradients) factors jointly shaped community composition of this species along the multiple spatial scales, (3) biotic interactions have a prominent effect on the community composition of this species at local-scale while macroclimatic gradients impose the major control on it at macro-scale. Thus, this study highlights the significance of host specificity in affecting the wood-boring longhorn beetle community assemblage, particularly at local scales.

Figure 1

Insect species (dark grey) and plant species’ (light grey) bsor (overall beta diversity), bnes (nestedness component of bsor), and bsim (replacement component of bsor) was calculated between the survey plots (25 × 20 m²) at different spatial distances: (1) plots within transects (β₁: 40–100 m scale), (2) plots between two neighboring transects within a region (β₂: 200–300 m scale), (3) plots between two transects covering the highest elevation gradient within a region (β₃: 1–3 km scale), (4) plots between two neighboring regions (δ₁: 250–300 km scale), and (5) plots between two regions covering the highest spatial distance (δ₂: > 500 km scale). White dots represent medians, thick black bars represent first quartiles and thin black lines represent the range. The shape of each plot shows the frequency distribution of the data. *, ** and ***Significant differences in β-diversity between insects and plants at each spatial scale and region (significance codes: ***P < 0.001, **P < 0.01, *P < 0.05).

Figure 2

Variation partitioning results of redundancy analysis testing for the influence of plant community composition, plant phylogeny, environmental variation (elevation metrics, humidity metrics and temperature metrics) and spatial distance on wood-boring longhorn beetle composition in the Yunnan province, SW China. Pla plant species composition, PlaPhy plant phylogeny, Spa spatial distance, Ele elevation metrics, Hum humidity metrics, Tem temperature metrics.

Figure 3

Geographical location of the three sampling sites, nine sampling transects and 45 sampling plots in the east Himalayan Mountains, Yunnan province, Southwest China, the basic map is generated in R 3.4.5, and ‘.shp’ file is from the open resources of National Catalogue of Service For Geographic Information (https://www.webmap.cn/main.do?method=index) under the regulations of Surveying and Mapping Law of the People's Republic of China (2017), and the sampling topographic map is generated with Google earth (Google Earth Pro 7.3.3.7786 (64-bit)) with the permission of GOOGLE TERMS OF SERVICE (https://policies.google.com/terms?hl=en).