Disturbance frequency and community structure in a twenty-five year intervention study

Abstract

Models of community regulation commonly incorporate gradients of disturbance inversely related to the role of biotic interactions in regulating intermediate trophic levels. Higher trophic-level organisms are predicted to be more strongly limited by intermediate levels of disturbance than are the organisms they consume. We used a manipulation of the frequency of hydrological disturbance in an intervention analysis to examine its effects on small-fish communities in the Everglades, USA. From 1978 to 2002, we monitored fishes at one long-hydroperiod (average 350 days) and at one short-hydroperiod (average 259 days; monitoring started here in 1985) site. At a third site, managers intervened in 1985 to diminish the frequency and duration of marsh drying. By the late 1990s, the successional dynamics of density and relative abundance at the intervention site converged on those of the long-hydroperiod site. Community change was manifested over 3 to 5 years following a dry-down if a site remained inundated; the number of days since the most recent drying event and length of the preceding dry period were useful for predicting population dynamics. Community dissimilarity was positively correlated with the time since last dry. Community dynamics resulted from change in the relative abundance of three groups of species linked by life-history responses to drought. Drought frequency and intensity covaried in response to hydrological manipulation at the landscape scale; community-level successional dynamics converged on a relatively small range of species compositions when drought return-time extended beyond 4 years. The density of small fishes increased with diminution of drought frequency, consistent with disturbance-limited community structure; less-frequent drying than experienced in this study (i.e., longer return times) yields predator-dominated regulation of small-fish communities in some parts of the Everglades.

Assembly rules in Muscid Fly assemblages in the grasslands Biome of Southern Brazil

“…The spatial scale of the disturbance can determine the capacity of colonization of local habitats by potential colonizers, thus strongly influencing the structure and function of communities according to the historical trajectory of the disturbance (Welborn et al 1996, Trexler et al 2005. In the case of the Grasslands biome, seasonal variation in temperature, humidity, rainfall, photoperiod, and productivity regulate population sizes and decrease the pressure on resources.…”

Fish functional groups in a tropical wetland of the Yucatan Peninsula, Mexico

“…It provides a unique opportunity for the study of the structure and drivers of fish communities in a freshwater wetland that lacks anthropogenic alterations (Zambrano et al, 2006). These wetlands have a clear seasonal hydroperiod (wet and dry seasons), therefore fish communities experience habitat contractions and a high mortality rate during the dry season (Loftus & Kushlan, 1987;Trexler et al, 2005). In SKBR, wetlands are constituted by permanent and temporary pools and their connection depend on hydro-meteorological conditions (Zambrano et al, 2006).…”

Resource Partitioning Among Three Mesoconsumers at a Marsh Mangrove Ecotone: a Response to a Seasonal Resource Pulse Subsidy

“…Snook are a tropical euryhaline ambush piscivore found throughout the Caribbean in habitats ranging from land-locked freshwater lakes to offshore reefs (Blewett et al 2006;Muller and Taylor 2006;Adams et al 2011). Largemouth bass and bowfin are mesopredators found throughout Everglades freshwater marshes, including natural (Chick et al 2004;Trexler et al 2005) and man-made habitats (e.g., canals; Rehage and Trexler 2006). Largemouth bass are a temperate cruising piscivore (Carey and Wahl 2010;Norris et al 2010).…”

“…As rainfall decreases in the dry season, water levels drop and marshes dry, effectively reducing habitat availability and quality. In response to this seasonal drydown, fish and other aquatic organisms disperse to the deepest habitats in the landscape (i.e., solution and alligator holes, central sloughs and canals; Trexler et al 2005;Rehage and Trexler 2006;Rehage and Loftus 2007;Parkos et al 2011). …”