Phylogenetic and functional diversity could be better indicators of macroinvertebrate community stability

It is essential to understand biodiversity's contribution to maintaining river ecosystem functioning and stability, which will us help to develop more effective strategies for river ecosystem conservation. However, knowledge regarding the relationship between multidimensional characteristics of biodiversity and ecosystem functioning and stability in aquatic ecosystems remains limited. This study examined the relationships between macroinvertebrate multidimensional diversity, secondary productivity, and secondary productivity/biomass (P/B) ratios in natural river ecosystems to examine which kind of diversity could best indicate community stability. In this study, macroinvertebrates were extensively sampled from Chishui River (CSH, an undammed river) and Heishui River (HSH, a dammed river) in April and September 2019. We comparatively analyzed seasonal variations in different types of diversity (species diversity, SD; phylogenetic diversity, PD; and functional diversity, FD), secondary productivity, and P/B ratios between the two rivers. Structural equation models were used to reveal the relationships between multidimensional diversity, secondary productivity, and P/B ratios. The results showed that SD significantly decreased during September both in the undammed CSH which has dramatic seasonal hydrological fluctuations, and in dammed HSH which has stable seasonal hydrological conditions. These findings indicated that SD could not clearly distinguish the key factors that cause changes in biodiversity. Conversely, both PD and FD significantly declined during September in the undammed CSH, but they did not significantly change in the dammed HSH. This result indicated that PD and FD are more sensitive than SD for identifying the effects of disturbances on biodiversity in these natural river ecosystems. After severe hydrological disturbance, although species abundance, biomass, biodiversity, and secondary productivity decreased in CSH, the still high value of P/B ratios indicated the high functional redundancy of communities, which further demonstrated the high stability of macroinvertebrates in CSH. Structural equation models revealed that the effects of PD and FD on secondary productivity and P/B ratios were more significant than those of SD in both rivers, which suggested that PD and FD may be better indicators of macroinvertebrate community stability than SD in these natural river ecosystems. Our study provides evidence that biological functional traits and evolutionary history can help achieve a more complete understanding of biodiversity patterns that maintain river ecosystem functioning and stability.

Automated summary

This study compared the seasonal variations of different types of diversity between Chishui River and Heishui River, revealing that phylogenetic diversity (PD) and functional diversity (FD) are more sensitive than species diversity (SD) in indicating the effects of disturbances on biodiversity. Structural equation models showed that PD and FD had more significant effects on secondary productivity and P/B ratios than SD, suggesting that PD and FD may be better indicators of macroinvertebrate community stability in these natural river ecosystems.