Fragmentation and drying ratchet down Great Plains stream fish diversity

Abstract

Stream fragmentation alters the structure of aquatic communities on a global scale, generally through loss of native species. Among riverscapes in the Great Plains of North America, stream fragmentation and hydrologic alteration (flow regulation and dewatering) are implicated in the decline of native fish diversity. This study documents the spatio–temporal distribution of fish reproductive guilds in the fragmented Arkansas and Ninnescah rivers of south‐central Kansas using retrospective analyses involving 63 years of fish community data. Pelagic‐spawning fishes declined throughout the study area during 1950–2013, including Arkansas River shiner (Notropis girardi) last reported in 1983, plains minnow (Hybognathus placitus) in 2006, and peppered chub (Macrhybopsis tetranema) in 2012. Longitudinal patterns in fish community structure in both rivers consisted of strong breaks associated with dams, and pelagic‐spawning fishes were missing from shorter fragments upstream of those barriers. Among downstream and longer fragments, probability of occurrence for pelagic‐spawning fishes declined or fell to zero during periods of drought. Based on these data, interactions between fragmentation and drying are hypothesized as operating as an ecological ratchet mechanism in which forward movement toward pelagic‐spawning fish extirpation occurs during desiccation, and reciprocated reverse movement toward recolonization following return of flows is blocked by fragmentation. The ratchet mechanism is capable of explaining the long‐term 'ratcheting down' of fish diversity in Great Plains rivers and has implications for managing biodiversity in fragmented riverscapes where water is scarce or might become so in the future. Copyright © 2014 John Wiley & Sons, Ltd.

Comparative riverscape genetics reveals reservoirs of genetic diversity for conservation and restoration of Great Plains fishes

“…A major difference between fishes belonging to this guild and most pelagic-spawning fishes is the ability to inhabit and reproduce within reservoirs, which has likely helped to buffer pelagic-substrate spawning fishes against the effects of fragmentation and dewatering throughout the Great Plains (Perkin et al 2014a). In fact, reservoirs are implicated in the expansion of N. atherinoides upstream of reservoirs (Pflieger and Grace 1987; Hoagstrom and Turner 2013), which provides some clue as to the mechanism behind the enigmatic pattern by which N. atherinoides is vulnerable to the effects of fragmentation but has also shown long-term increases in abundance for some Great Plains streams (Perkin et al 2014a, b). Finally, C. lutrensis was widely persistent even among the most highly fragmented and dewatered stream fragments included in this study and might not be expected to respond to fragmentation at such broad spatial extents, though there is evidence that the species is vulnerable to the effects of isolation at smaller scales (Matthews and Marsh-Matthews 2007).…”

“…However, in this species high variance in reproductive success among spawning aggregations caused by the interaction of fragmentation and pelagic early life-history is likely responsible for the small effective to census size ratio observed in H. amarus (Aló and Turner 2005; Turner et al 2006; Osborne et al 2005). In the most vulnerable species considered here ( H. placitus ) and those that share its pelagic life-history (but that were not detected in short fragments; Perkin et al 2014a) it is plausible that stochastic forces such as drought ultimately determine the fate of populations rather than negative genetic impacts (Kelsch 1994; Perkin et al 2014b). Numerous studies have demonstrated that factors including short life-span combined with increased isolation from other populations and occasional absence of reproduction/or recruitment (e.g., caused by absence of spawning cues such as spring runoff, Bonner and Wilde 2000), cause strong fluctuations in population size and thereby increase extinction risk (Leigh 1981; Pimm et al 1988; Sjogren 1991).…”

“…Numerous studies have demonstrated that factors including short life-span combined with increased isolation from other populations and occasional absence of reproduction/or recruitment (e.g., caused by absence of spawning cues such as spring runoff, Bonner and Wilde 2000), cause strong fluctuations in population size and thereby increase extinction risk (Leigh 1981; Pimm et al 1988; Sjogren 1991). Historical and contemporary periods of drought (Matthews and Marsh-Matthews 2007; Perkin et al 2013; Perkin et al 2014b) combined with negative effects of fragmentation (Winston et al 1991; Luttrell et al 1999; Wilde and Ostrand 1999), are thought to have eliminated populations of endemic fish, particularly pelagic-spawning species (Kelsch 1994). Specifically, Perkin et al (2014b), hypothesize that the disappearance of three pelagic spawning species (Arkansas River Shiner, Plains Minnow and Peppered Chub) from the Arkansas and Ninnescah Rivers were related to the effects of fragmentation and periodic droughts over the past few decades.…”

Advancing Environmental Flow Science: Developing Frameworks for Altered Landscapes and Integrating Efforts Across Disciplines

“…Major declines in baseflow lead to the loss of longitudinal connectivity that over time has important consequences for the persistence of many riverine populations (Bunn and Arthington 2002). This effect is particularly evident with repeated stream drying in fragmented stream systems of the Great Plains (Perkin et al 2014). Decreased flows in arid streams exacerbate the influence of non-native predators on fish populations, perhaps by creating less favorable habitat conditions for flow-adapted native species, though the possible mechanisms remain unclear (Propst et al 2008).…”

Long-Term Monitoring Data Provide Evidence of Declining Species Richness in a River Valued for Biodiversity Conservation

“…These taxa represent diverse phylogenies (two cyprinids, one ictalurid, and one percid), feeding behaviors (i.e., water-column and benthic foragers), and spawning modes (i.e., crevice-spawning, broadcast-spawning, nest-guarding, and gravel spawning). Whereas species traits have proven useful in identifying fishes that are most responsive to environmental change in other contexts (Craven et al 2010;Carlisle et al 2011;Mims and Olden 2012;Perkin et al 2015), there are no obvious unifying traits among these declining taxa. At the same time, three of the declining taxa have one or more congeners (i.e., species with likely similar traits) that do not show evidence of decline at the Conasauga River sites.…”