Analysis of keystone species in a quantitative network perspective based on stable isotopes

The analysis of keystone species based on network structure has increasingly emphasized the significance of quantitative food webs. In this study, Zhangze Lake was chosen as the research subject, and assigned a weighted index to each index by creatively combined isotope techniques with topological important and uniqueness theories, then united centrality theory. Next, various scales of indices were used to examine the importance of each nutrient in the food web, the correlation between the ordering and distribution across indices, and the difference in time. This study revealed that the centrality of phytoplankton was significantly higher in April compared to July. Both of the monthly unique species in this ecosystem were planktivorous feeders, while the keystone species serving as higher consumers were identified to be Exopalaemon modestus. The ranking results of the indices other than the weighted closeness centrality and weighted betweenness centrality showed consistency. Additionally, the distributions of the weighted indices differed significantly from their corresponding unweighted indices, with the weighted centrality indices being more similar to the out-degree ordering and more strongly correlated in April. When only strong interactions between species were considered, there was a negative correlation found between species centrality and uniqueness. Through the quantitative construction of a diet proportion food web model, combined with multiple indices, we have provided a practical solution for holistically and quantitatively identifying key species, thus aiding in the accurate and effective protection of biodiversity.