Species co-occurrence can examine whether and why two or more species co-exist. However, the understanding of the relevant mechanism remains a challenging. Previous studies have suggested that various biotic and abiotic factors might play important roles in species coexistence, and that these factors are highly correlated with niche partitioning as well as trade-offs of species life history However, it is still unclear how phylogenetic distance and functional traits affect co-occurrence within two trophic levels.
Here, Chao-Dong Zhu’s Lab (Insititute of Zoology, Chinese Academy of Sciences) analysed co-occurrence of pairs of caterpillar species in a subtropical forest, and examined how these might be influenced by Lepidoptera phylogenetic distance across three spatial scales (tree individual, tree species, and plot levels). The study also considered the potential effects from diversity and functional traits of trees, and other environmental predictors. They explored the interrelationships of phylogenetic distance of caterpillars, several measures of tree diversity and tree functional traits on Lepidoptera species co-occurrence.
The study found Lepidoptera species co-occurrence to be negatively associated with phylogenetic distance of both Lepidoptera and trees, with phylogenetic clustering patterns across the three spatial scales, supporting an overall strong effect of environmental filtering. They also found Lepidoptera species co-occurrence was positively associated with nutritional functional traits (e.g. C:N concentrations), but negatively with defensive traits (e.g. leaf toughness) and the tree diversity of the tree communities. Moreover, Lepidoptera species co-occurrence was much lower at smaller spatial scales (individual tree level), compared to larger (tree species or plot levels), supporting the competition exclusion principles for the smallest spatial scale. The findings provide new insights into how coexistence pattern of herbivores are driven by herbivore phylogenetic relatedness and the functional traits and diversity of their host plants. The results depict for a highly diverse group of insect herbivores that various driving forces, in particular environmental filtering, play a significant role in determining the species coexistences in herbivore communities via species interactions, and that the relative importance of these forces varies from local to larger spatial scales within the host communities.
Figure 2: Relationships between Lepidoptera co-occurrence and phylogenetic distance at (a) tree individual level, (b) tree species level and (c) study plot level; and the relationships between the mean values of co-occurrence and grouped phylogenetic distance at (d) tree individual level, (e) tree species level and (f) study plot level.
Figure 3: Relationships between co-occurrence and (a) ratio of leaf carbon to nitrogen concentrations, (b) leaf toughness and (c) tree height at tree species level; as well as relationships between co-occurrence and (d) tree species richness, (e) tree mean pairwise distance and (f) community-weighted mean value of specific leaf area at study plot level. Values were adjusted for covariates of the final regression model.
The study was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB310304), the National Science Fund for Distinguished Young Scholars (31625024) and other programs to Chao-Dong Zhu’s Lab.
Mingqiang Wang, Chuan Yan, Arong Luo, Yi Li, Douglas Chesters, Huijie Qiao, Jingting Chen, Qingsong Zhou, Keping Ma, Helge Bruelheide, Andreas Schuldt, Zhibin Zhang, and Chaodong Zhu*. 2021. Phylogenetic relatedness, functional traits, and spatial scale determine herbivore co‐occurrence in a subtropical forest. Ecological Monographs. Online. https://doi.org/10.1002/ecm.1492.