山区河流生物生态位及种间联结对人为干扰的响应OACHSSCD

In order to investigate the structure of multiple biotic communities and the niche characteristics of dominant species in river ecosystems,as well as their response to anthropogenic disturbance,field surveys of diatom,macroinvertebrates,and fish were carried out in 2021 and 2024 using environmental DNA(eDNA)technology.A total of 10 sampling sites was conducted across varying levels of anthropogenic disturbance-low,moderate and high-in the southern mountainous rivers of Jinan City.The Jaccard similarity coefficient was adapted to identify differences in dominant species composition;Shannon and Pianka indices were used to assess niche breadth(Bi)and overlap(Oik)across aquatic groups;variance ratio(VR),chi-square test(x2),and interspecific association coefficients(AC)were calculated to evaluate overall community connectivity and interspecific association among dominant species;and a cross-trophic co-occurrence network was constructed to analyze the stability of aquatic communities.The results showed that:(1)A total of 118 genera(species)of aquatic organisms,belonging to 6 phyla and 9 classes,were detected.Among these,74 genera(species)across the same taxonomic ranks were identified as dominant species based on the Mcnaughton dominance index(Y＞0.02).No significant differences were observed in dominant species composition across disturbance levels,and neither niche breadth(Bi)nor overlap(Oik)showed significant variation(P＞0.05).However,average Bi and Oik values followed the order:diatoms(Bi:2.09-3.64,Oik:0.50-0.69)＞fish(Bi:1.24-3.11,Oik:0.38-0.58)＞macroinvertebrates(Bi:0.40-3.30,Oik:0.32-0.58),indicating that diatom dominants exhibited high resource-use similarity and strong interspecific competition,while in contrast to the other two groups,macroinvertebrates exhibited weaker competitive ability.(2)Except for the high disturbance zone in 2024,overall interspecific associations of aquatic organisms were significantly positive(VR＞1,W＜x20.95 or W＞x20.05),suggesting stable community structures across disturbance zones.(3) x2 test,AC and the cross-trophic co-occurrence network consistently indicated that interspecific associations among dominant species were predominantly significantly positive.Negative associations were primarily driven by predation from higher-to-lower trophic level organisms,with competition among dominant species within the same functional group playing a secondary role.From this,under the current level of anthropogenic disturbance,the aquatic biological communities have formed complex and balanced interaction patterns in each disturbance zone,reaching a fundamentally stable state.