Climate extremes drive changes in functional community structure

Abstract

The response of communities to climate extremes can be quite variable. Much of this variation has been attributed to differences in community-specific functional trait diversity, as well as community composition. Yet, few if any studies have explicitly tested the response of the functional trait structure of communities following climate extremes (CEs). Recently in South Florida, two independent, but sequential potential CEs took place, a 2010 cold front, followed by a 2011 drought, both of which had profound impacts on a subtropical estuarine fish community. These CEs provided an opportunity to test whether the structure of South Florida fish communities following each extreme was a result of species-specific differences in functional traits. From historical temperature (1927-2012) and freshwater inflows records into the estuary (1955-2012), we determined that the cold front was a statistically extreme disturbance, while the drought was not, but rather a decadal rare disturbance. The two disturbances predictably affected different parts of functional community structure and thus different component species. The cold front virtually eliminated tropical species, including large-bodied snook, mojarra species, nonnative cichlids, and striped mullet, while having little affect on temperate fishes. Likewise, the drought severely impacted freshwater fishes including Florida gar, bowfin, and two centrarchids, with little effect on euryhaline species. Our findings illustrate the ability of this approach to predict and detect both the filtering effects of different types of disturbances and the implications of the resulting changes in community structure. Further, we highlight the value of this approach to developing predictive frameworks for better understanding community responses to global change.

Collapse of a reproducing population of non-native African jewelfish (Hemichromis letourneuxi) in a Florida lake

“…One of the most prevalent mechanisms to explain boom-and-bust cycles of native fishes is the effect of the interaction of environmental factors and life history traits on annual recruitment (e.g., Lobon-Cervia 2009, Matthews and MarshMatthews 2011). This is likely a rich area of future research investigating population fluctuations of Florida non-natives (e.g., the influence of major cold events; Schofield et al 2010, Harrison et al 2013, Boucek and Rehage 2014. As suggested by the present study, biotic resistance through predation likewise may prove an important mechanism.…”

“…Predation by native species is seldom thought to be the cause of these newer examples (but see Sheehy and Lawton 2014). Boom-and-bust cycles and spontaneous population collapse for non-native fishes in Florida are mentioned in the literature but accounts are largely anecdotal (but see Harrison et al 2013 andBoucek and for cold effects). Although cichlids are among the most numerous and successful established non-native fishes in Florida (Shafland et al 2008), population abundance and range of several species have fluctuated considerably and some species have disappeared from the state, generally with no known cause (Shafland 1996, Shafland et al 2008, USGS 2015.…”

Long-term functional changes in an estuarine fish assemblage

“…A major breakthrough in community ecology studies has been the incorporation of functional approaches and functional diversity measures, as an elucidating tool to explore species coexistence and impacts on ecosystem functioning (Mouillot et al, 2007(Mouillot et al, , 2013Boucek and Rehage, 2014). Functional diversity refers to the functional component of biodiversity and is usually measured by species traits (Violle et al, 2007).…”

Opposing forces: Evaluating multiple ecological roles of Pacific salmon in coastal stream ecosystems

“…Spiller et al (2010) found that the abundance of terrestrial predators increased with marine subsidies on islands, while Boucek and Rehage (2014) found that disturbance from two extreme climate events greatly altered fish community composition. However, there is a unique and well-known example in nature where a substantial resource pulse and disturbance occur simultaneously.…”