The river continuum concept predicts prey assemblage structure for an insectivorous fish along a temperate riverscape

Abstract

The river continuum concept (RCC) provides a framework for processes structuring lotic ecosystems by synthesizing sources and transport of C in streams. Considerable attention, refinement, and testing of the RCC has occurred since its inception >35 y ago, but few investigators have tested its predictions by explicitly linking consumer groups. We assessed insect assemblage structure in the diet of a broadly distributed insectivorous fish (Cottus carolinae) in the Roaring River continuum of Tennessee to test 3 predictions from the RCC: 1) longitudinal change in relative biomass of insect functional feeding groups (FFGs) including decrease for shredders, increase for collectors, intermediate maximum for grazers, and consistency for predators; 2) maximum taxonomic diversity at stream orders 3 to 5; and 3) temporal turnover in taxonomic composition across 1 y. We found that relative biomass of insect FFGs consumed by C. carolinae broadly matched predictions from the RCC. Maximum taxonomic diversity assessed at the family rank occurred at stream order 4 where diel and annual water temperature fluctuations were greatest, and monthly prey assemblages followed a sequence of turnover and a return to starting conditions across 1 y. Our novel approach illustrates proof of concept that RCC tenets are integrated into the diet of at least 1 higher-level consumer and, therefore, transcend assemblage boundaries in regulating the longitudinal (up-to downstream) and vertical (multiple consumer groups) flow of C in streams.

The River Continuum Concept: lessons from the past and perspectives for the future

“…Africa Chakona et al 2008;Bredenhand and Samways 2009;Masese et al 2014Masese et al , 2018Dalu et al 2017Asia Qu et al 2005Xiaocheng et al 2008;Lau et al 2009;Jiang et al 2010Jiang et al , 2011Gao et al 2014;Fu et al 2016Australasia Winterbourn et al 1981; Barmuta and Lake 1982;Winterbourn 1982;Lake et al 1985;Ryder and Scott 1988;Harding et al 1999;Thompson andTownsend 2000 Europe Heino et al 2005;Maiolini and Bruno 2006;Manfrin et al 2013;Dossi et al 2018 North America Culp andDavies 1982;Perry and Schaeffer 1987;Grubaugh et al 1996;Delong and Brusven 1998;Rice et al 2001;Rosi-Marshall and Wallace 2002;Grubbs and Taylor 2004;Greathouse and Pringle 2006;Lessard et al 2009;Holt et al 2015;Rosi-Marshall et al 2016;Yates et al 2018;Curtis et al 2018South America Afonso et al 2000Callisto et al 2004;Tomanova et al 2006Tomanova et al , 2007Miserendino 2009;…”

Testing the River Continuum Concept with geostatistical stream-network models

“…Thorp et al, 2006), it remains one of the most influential concepts in river science (4.949 citations as of Match 2019; ISI Web of Science database). One of the key strengths of the RCC is that it proposes testable hypotheses regarding changes in stream metabolism (P/ R), the main trophic basis of production (carbon sources) and the consequent adjustment of consumer communities (functional feeding groups; Cummins, 2016) Empirical tests of the RCC provided support for its predictions, especially in temperate North American rivers (Curtis et al, 2018;Hawkins and Sedell, 1981;Minshall et al, 1985Minshall et al, , 1983Rosi-Marshall and Wallace, 2002;Webster, 2007), and more recently in different biomes and climatic zones (Greathouse and Pringle, 2006;Jiang et al, 2011;Tomanova et al, 2007). Studies that have criticised the RCC generally emphasise the local heterogeneity of river systems (Perry and Schaeffer, 1987;Statzner and Higler, 1985;Townsend, 1989).…”

Spatial and seasonal variation in host community structure is weakly concordant with patterns of parasite composition

“…For example, within drainage systems macroinvertebrates were shown to respond strongly to pH and stream size, while fish respond strongly to stream depth (Paavola et al., 2003). These subsets of environmental variables, stream size and stream depth, serve as proxies for other important variables for each taxonomic group, such as resource and prey availability that directly impact consumer composition (Curtis et al., 2018; Goldstein & Meador, 2004). Similarly, parasites and their hosts may respond to a different subset of environmental or biological factors at local scales.…”

“…(Minshall et al., 1983). These changes in resource types inform the expectation that macroinvertebrate functional feeding groups will vary spatially (Cummins & Klug, 1979; Rosi‐Marshall et al., 2016; Rosi‐marshall & Wallace, 2002), with concurrent shifts in the community structure in higher‐order consumers such as fish (Curtis et al., 2018; Goldstein & Meador, 2005; Schlosser, 1982).…”