Contributions of rare and common species to the species diversity of the mangrove macrobenthic community in Aojiang Estuary

Species diversity is closely related to the composition of rare and common species in the community. However, their contribution to community species diversity remains controversial, studying the relationship between rare species and species diversity is helpful to better understand the mechanism of community construction. We calculated the α-diversity and β-diversity of the community, combined with geographic range(gri), habitat specificity index (hsi) and population size index (psi) recognition community rare species to investigate the effects of rare and common species on α-diversity and β-diversity of macrobenthos community, and to reveal the basic process of community construction, mangrove macrobenthos in Aojiang Estuary were as the research object in this experiment. Meanwhile, the species were sorted according to their rarity, forming two species sequences of rare species - common species and common species - rare species. On this basis, the relative contributions of rare and common species to species diversity were determined by comparing the changes in species diversity (α-diversity and β-diversity) by adding species one by one. The results showed that a total of 47 species of macrobenthos were identified in the mangroves of Aojiang Estuary from 2017 to 2020. The α diversity of mangroves in spring and autumn was higher than that in summer and winter. The β diversity was similar in four seasons, mainly dominated by nested components. The α-diversity increased first and then decreased with the addition of species to Shannon-Wiener diversity index and richness index in rare species-common species sequence, while evenness index only increased first and then decreased in 2020, and the rest showed a downward trend. Shannon-Wiener diversity index and richness index showed an increasing trend, while evenness index showed a decreasing trend with the addition of species in the common-rare species sequence. β-diversity increased with the addition of species to community heterogeneity (β_SOR) and nested component (β_NES), while turnover component (β_SIM) decreased in the rare species to common species sequence. In the sequence of common species and rare species, β_SOR, β_SIM, and β_NES increased with the addition of species. In conclusion, rarity index could accurately and effectively identify rare species in the community, the rare species contributed more to community α diversity and affected the turnover component of community β diversity, while the common species had a greater impact on the nested component. Therefore, different ecological conservation strategies should be adopted for different species, these results of this study provide theoretical support for mangrove ecological protection in Aojiang Estuary to better protect the mangrove ecosystem in this region.