Functional responses of stream fish communities to rural and urban land uses

Abstract

We tested the effects of ruralization and urbanization on the functional diversity indices and the composition of functional traits of Neotropical stream fish communities. The study was carried out in 24 streams of the Pirapó, Piquiri, Paraná III and Iguassu river basins. Land use in the watershed was categorized as percentages of native vegetation, rural occupation and urban occupation. Statistical tests revealed negative bivariate correlations between functional dispersion and the proportion of native vegetation in the watershed. The results indicate that a higher percentage of rural or urban occupation is associated with increased functional dispersion. In the analyzes of trait composition, significant alterations were observed in response to urbanization while only the increase in herbivory responded to ruralization. As the area of native vegetation is reduced by urbanization, the trait composition changes, with reduced proportions of species with intolerance to hypoxia, migratory reproductive behavior, external fertilization, and subterminal mouth, and increased proportions of species with parental care, detritivory, internal fertilization, and an upper mouth. Therefore, fish species that have these specific characteristics are more likely to disappear from streams as urbanization progresses. In summary, urbanization was related to a greater change in the composition of functional traits than ruralization.

Functional diversity does not explain the co‐occurrence of non‐native species within a flow‐modified African river system

“…Specifically, the results of the fourth-corner analyses, which indicated non-significant species-trait-environmental relationship, suggest that species functional traits were not major drivers of fish community structure in the Great Fish River. These findings are in contrast to other studies that have found significant associations between environmental variables and fish species traits, highlighting the role and importance of species functional traits in shaping fish community structure in aquatic environments (Brind'Amour et al, 2011;Er} os et al, 2009;Miiller et al, 2021;Pease et al, 2012;Ribeiro et al, 2016). The lack of significant trait-environment association in the present study may suggest that environmental filtering was a weak determinant of functional trait structure (Asefa et al, 2017), and that functional traits used in this study were a poor indicator of resource use patterns for fishes of the Great Fish River.…”

“…Species functional traits can be used to better understand fish assemblage structure (Pease et al, 2012; Walsh et al, 2022), quantify the trait‐environment relationships (Brind'Amour et al, 2011; dos Santos et al, 2017; Santos et al, 2019) and assess the response of ecosystem to disturbances, including the introduction of non‐native species into novel environments (Angulo‐Valencia et al, 2022; Dala‐Corte et al, 2016; Lin et al, 2021; Miiller et al, 2021). Consistent with the first hypothesis that functional traits would reflect broad differences in species and their habitat associations within the Great Fish River system, the results of the present study revealed evidence of interspecific variation in functional traits, which appeared to reflect spatial differences in the distribution patterns and species‐environmental relationships.…”

Shifting taxonomic and functional community composition of rivers under land use change

“…By contrast, functional community responses to land use according to specific species traits were much more similar across space. Fish communities facing intensified land use practices have been found to favor species traits associated with general physical habitat requirements, warmer thermal preference, more rapid life cycle, opportunistic feeders, and greater parental care of offspring (e.g., Comte et al, 2021; Miiller et al, 2021; Pease et al, 2015; Zeni & Casatti, 2014; also see discussion below). Increasing land use change shifts invertebrate community composition toward those species exhibiting sedentary habits, collector feeding behavior, warmer eurythermal preferences, effective dispersal capacity, multivoltine taxa, and shorter life cycle (e.g., Barnum et al, 2017; Krynak & Yates, 2018; Larsen & Ormerod, 2010).…”

“…However, the directionality of trait responses was largely consistent with theoretical expectations and empirical findings reported at regional scales. Intense land use alteration acts as an environmental filter selecting for opportunistic life history strategists with broad, generalized niches (Barnum et al, 2017; Comte et al, 2021; Dala‐Corte et al, 2016; Miiller et al, 2021). For example, bank erosion and altered flow regime degrade streambeds through excess siltation and scour, causing the loss of bottom‐dwelling organisms that require clean gravel with interstitial spaces (Barnum et al, 2017; Dala‐Corte et al, 2016).…”

“…Anthropogenic heat effluent or increase incoming radiation due to urbanization and removal of riparian vegetation led to stream warming that favors warmwater species (Brumm et al, 2023; Comte et al, 2021). Greater parental care increases survival and recruitment of fish species in altered urban and agricultural habitats (Miiller et al, 2021). Opportunistic life‐history strategies (e.g., short life cycle, rapid maturation, high fecundity, and small body size) confer high community resilience (Townsend & Hildrew, 1994), which is advantageous in urban and agricultural habitats subjected to frequent and/or unpredictable changes (Mims & Olden, 2012; Pease et al, 2015).…”