Anthropogenic disturbances affect the functional diversity of stream fishes and its longitudinal patterns in China

Abstract

Aims:The distribution and abundance of stream fishes are influenced by historical events as well as abiotic and biotic factors. Due to the high spatial heterogeneity and temporal differentiation of stream environmental characteristics, the composition and abundance of stream fish communities vary on spatial and temporal scales. On this basis, longitudinal patterns in the diversity and distribution of stream fish along upstream-downstream gradients have garnered the widespread attention of ecologists. Previous studies relevant to the longitudinal patterns in stream fish diversity along the upstream-downstream gradient mostly focused on taxonomic α diversity, while taxonomic β diversity and functional diversity have been given less attention. Therefore, this study aimed to (1) determine the effects of anthropogenic disturbances on species composition of fishes by comparing diversity across three streams, and determine the key species contributing to the between-stream variation in fish assemblages; (2) examine the influences of anthropogenic disturbances on functional diversity, and examine if differences in functional diversity relate to α and β diversity; (3) to assess whether the between-stream variations in functional diversity show dependence on the spatial positions along the river continuum or not, and further assess the effects of anthropogenic disturbances on the longitudinal patterns in the

Effects of overgrazing on the functional diversity of rodents in desert areas

“…The Functional Divergence Index was higher in the overgrazing areas than in the grazing prohibition areas, indicating that in each season, the dominant species in the grazing prohibition areas were close to the center of gravity of the functional space, the niche space overlap effect was strong, and the resource competition among species was fierce (Jiang, 2010; Zhang & Fan, 2011). However, overgrazing increased the functional heterogeneity of the community (He et al., 2021), so that the dominant species were at the edge of the functional space, the niche differentiation of the community was high, and the rodents used the existing resources in different ways (Zhang et al., 2019). In addition, due to differences in food resources between seasons, the overgrazing community has dominant species with a smaller body size (Yuan et al., 2013) in order to adapt to the harsh environment because the existence of rodents occupying smaller niches reduces the competition for food resources, can reduce the degree of niche overlap, and makes full use of food resources (Tinoco et al., 2018).…”

“…However, overgrazing increased the functional heterogeneity of the community (He et al, 2021), so that the dominant species were at the edge of the functional space, the niche differentiation of the community was high, and the rodents used the existing resources in different ways (Zhang et al, 2019). In addition, due to differences in food resources between seasons, the overgrazing community has dominant species with a smaller body size (Yuan et al, 2013) in order to adapt to the harsh environment because the existence of rodents occupying smaller niches reduces the competition for food resources, can reduce the degree of niche overlap, and makes full use of food resources (Tinoco et al, 2018).…”