Ecological effects of dams, alien fish, and physiochemical environmental factors on homogeneity/heterogeneity of fish community in four tributaries of the Pearl River in China

Abstract

In this study, we aimed to characterize the fish community structure and identify the drivers contributing to homogenization/differentiation processes in four tributaries to the Pearl River, Guangxi Province, China, over the past few decades. We sampled 22 sites seasonally from 2013 through 2015, and these sites were selected based on archived records of previous sampling conducted in the 1980s. Jaccard's faunal similarity index, cluster analysis, and canonical correspondence analysis (CCA) were applied to describe the homogenization/differentiation of fish community and illustrate the potential effectors. The number of fish species present in three of the four sampled tributaries declined dramatically over the past 30 years, leading toward a trend of increased fish community homogeneity throughout the watershed. Results from multidimensional scaling and cluster analyses allowed us to divide the study area into two distinct ecoregions. Four species (yellow catfish Pelteobagrus fulvidraco, pond loach Misgurnus anguillicaudatus, Nile tilapia Oreochromis niloticus, and sharpbelly Hemiculter leucisculus) were considered to be indicative fish species contributing more than 5% of the dissimilarity between the two eco‐regions according to the results of similarity percentage procedure. Results from CCA revealed that pH and latitude corresponded with the dominant fish species of each respective tributary. More specifically, CCA results allowed us to classify dominant fish species into three distinct groups. The first group was mainly located in Guijiang characterized by higher latitudes and lower pH values, the second group was widespread in the four tributaries, and the last group was primarily distributed in Yujiang, Youjiang, and Zuojiang characterized by lower latitudes and higher pH values. Spatial differentiation of fish community structure and temporal homogeneity of species composition were attributed to the joint actions of human interventions including construction of dams and introductions of exotic fish species that led to habitat degeneration and fragmentation, and unequal interspecies competitions.

Partitioning β-diversity reveals that invasions and extinctions promote the biotic homogenization of Chilean freshwater fish fauna

“…These findings expand on previous studies reporting incipient homogenization among the Chilean ichthyological provinces [41,42] and within the Neotropical realm [15,73]. A first implication of our results is that the Chilean basins share the generalized (global) homogenization trends, also recorded in other countries such as Australia [74], China [18][19][20], Japan [17], Portugal-Spain [13,75], European countries [76], and United States [11,12]. The importance of the analyses based on countries as study units lies in that-if biotic homogenization is an undesired byproduct of global biotic change [10]-it would be more feasible to stop or to revert, because countries can take appropriate actions and use political tools for their territorial management [77].…”

“…Although homogenization studies in freshwater fish assemblages are increasing, most part of them come from temperate latitudes of the Northern Hemisphere [e.g., [11][12][13][14][15][16][17][18][19][20], evidencing a remarkable geographical bias. Because the species diversity is differentially distributed between hemispheres, continents, and regions [2], it is desirable to know whether biotic homogenization occurs in areas beyond those most frequently reported [10,21].…”

Soil macro-fauna respond to environmental variations along a coastal-inland gradient

“…The richness and diversity in the 5H sampling line were observed to be the lowest. This was determined to be due to the fact that the lower effects of the sea resulted in the habitat of the 5H sampling line becoming more homogeneous (Zeng et al, 2017). Therefore, it was concluded that the homogeneity of the environmental conditions in the 5H sampling line had decreased the richness and diversity of the soil macro-faunal communities to some extent.…”

Avaliação das alterações hidrológicas da bacia do rio São Francisco causadas pela construção da usina hidrelétrica de Sobradinho

“…Estes resultados são semelhantes com os obtidos por Santos et al [17], que encontraram a diminuição de duração de vazões baixas e da frequência das vazões altas nos trechos de baixo São Francisco depois a construção dos principais reservatórios. Essa diminuição dos pulsos de baixa e alta leva a uma menor densidade das espécies de peixe, criando uma maior predação de outras espécies e atividade extrativista humana de pesca o que ocasiona escassez do recurso [38,39] e a introdução antrópica de espécies exóticas [36,[40][41][42]. O Grupo 5 dos indicadores avaliam a frequência de mudança das condições da água.…”