Application of taxonomic distinctness indices of littoral macroinvertebrate communities for assessing long-term variation in ecological quality status of intertidal ecosystems, northern China

Responses of multiple facets of macroinvertebrate alpha diversity to eutrophication in floodplain lakes

The accelerated eutrophication of freshwater lakes has become an environmental problem worldwide. Increasing numbers of studies highlight the need to incorporate functional and phylogenetic information of species into bioassessment programms, but it is still poorly understood how eutrophication affects multiple diversity facets of freshwater communities. Here, we assessed the responses of taxonomic, phylogenetic and functional diversity of benthic macroinvertebrates to water eutrophication in 33 lakes in the Yangtze River floodplain in China. Our results showed that macroinvertebrate assemblage structure was significantly different among four lake groups (river-connected, macrophyte-dominated, macrophyte-algae transition, and algae-dominated). Three taxonomic, two phylogenetic and two functional diversity indices were significantly different among the lake groups. Except for the increasing trend of Lambda⁺, these metrics showed a clear decreasing trend with increasing levels of eutrophication, with highest values detected in river-connected and macrophyte-dominated lakes, followed by macrophyte-algae transition lakes and algal-dominated lakes. Although differing in the number and identity of key environmental and spatial variables among the explanatory models of different diversity indices, environmental factors (eutrophication-related water quality variables) played more important role than spatial factors in structuring all three facets of alpha diversity. The predominant role of environmental filtering can be attributed to the strong eutrophication gradient across the studied lakes. Among the three diversity facets, functional diversity indices performed best in portraying anthropogenic disturbances, with variations in these indices being solely explained by environmental factors. Spatial factors were mostly weak or negligible in accounting for the variation in functional diversity indices, implying that trait-based indices are robust in portraying anthropogenic eutrophication in floodplain lakes. However, variation in some taxonomic and phylogenetic diversity indices were also affected by spatial factors, indicating that conservation practitioners and environmental managers should use these metrics with caution when providing solutions for addressing eutrophication in floodplain lakes.

Response of traditional and taxonomic distinctness diversity indices of benthic macroinvertebrates to environmental degradation gradient in a large Chinese shallow lake

A variety of biodiversity metrics are available to assess the quality of aquatic ecosystems. However, different types of metrics perform with considerable variation and provide various information involved in ecosystem conditions. Taxonomic distinctness (TD) indices have been recommended as desirable measures for assessing environmental degradation, but their utility based on lake macroinvertebrates is still largely unknown. Here, we evaluated the response of traditional and taxonomic distinctness diversity indices (the average taxonomic distinctness, Δ⁺, and variation in taxonomic distinctness, Λ⁺) of benthic macroinvertebrates to environmental degradation gradient in Lake Taihu, the third largest freshwater lake in China. Benthic assemblages responded markedly to human disturbances, with significance among-region differences in community composition throughout four seasons. The traditional biodiversity indices (Shannon-Wiener diversity and Pielou's evenness) showed high sensitivity in discriminating anthropogenic impacts, with highest values in macrophytic region but lowest values in eutrophic region. In contrast, Δ⁺ and Λ⁺ did not perform well in distinguishing sites subjected to different disturbance levels. The Pearson correlation and multiple regression analysis both indicated that traditional biodiversity metrics (Shannon-Wiener diversity, taxon richness, and Pielou's evenness) responded more readily to water quality variables (Secchi depth, electrical conductivity, and comprehensive trophic level index) than Δ⁺ and Λ⁺. Despite the weak correlations between TD indices of benthic macroinvertebrates and water quality in the present study, we suggest that the TD indices should still be considered in bioassessment programs because they provide useful complementary information on traditional diversity indices.

First report of the complete mitochondrial genome and phylogenetic analysis of Aphrodita australis (Aphroditidae, Annelida)

In this study, the complete mitochondrial genome of the Aphrodita australis was sequenced. The complete mitochondrial genome was circular and 15,288 bp in length, consisted of a typical set of 13 protein-coding genes (PCGs), 2 ribosomal RNA (rRNA) genes, 22 transfer RNA (tRNA) genes, and 1 non-coding control region. All these genes are in the heavy strand. The non-coding control region is 672 bp in length, and located between tRNA-Ser and tRNA-Leu. The overall nucleotides base composition of the heavy strand is 31.02% for A, 22.76% for C, 12.49% for G, and 33.73% for T, with a slight A + T-rich feature (64.75%). All of the PCGs begin with ATG as their start codon and the cox 3, cytb and nad 3 are terminated with TAA, atp8, nad4, nad 4l, and nad 6 are terminated with TAG, while others are terminated by incomplete codon T. Seen from the phylogenetic tree, A. australis has a more close relationship with Goniada japonica than other species.