The invasion ecology of sleeper populations: prevalence, persistence, and abrupt shifts

It is well established that nonnative species are a key driver of global environmental change, but much less is known about the underlying drivers of nonnative species outbreaks themselves. In the present article, we explore the concept and implications of nonnative sleeper populations in invasion dynamics. Such populations persist at low abundance for years or even decades—a period during which they often go undetected and have negligible impact—until they are triggered by an environmental factor to become highly abundant and disruptive. Population irruptions are commonly misinterpreted as a recent arrival of the nonnative species, but sleeper populations belie a more complex history of inconspicuous occurrence followed by an abrupt shift in abundance and ecological impact. In the present article, we identify mechanisms that can trigger their irruption, and the implications for invasive species risk assessment and management

Sweetened solution intake in albino rats: Taste versus calories [Consumo de soluciones endulzadas en ratas albinas: Sabor vs calorías]

Ecosystems are fragmented by natural and anthropogenic processes that affect organism movement and ecosystem dynamics. When a fragmentation restricts predator but not prey movement, then the prey produced on one side of an ecosystem edge can subsidize predators on the other side. When prey flux is high, predator density on the receiving side increases above that possible by in situ prey productivity, and when low, the formerly subsidized predators can impose strong top-down control of in situ prey-in situ prey experience apparent competition from the subsidy. If predators feed on some evolutionary clades of in situ prey over others, then subsidy-derived apparent competition will induce phylogenetic structure in prey composition. Dams fragment the serial nature of river ecosystems by prohibiting movement of organisms and restricting flowing water. In the river tailwater just below a large central Mexican dam, fish density was high and fish gorged on reservoir-derived zooplankton. When the dam was closed, water flow and the zooplankton subsidy ceased, densely packed pools of fish formed, fish switched to feed on in situ prey, and the tailwater macroinvertebrate community was phylogenetic structured. We derived expectations of structure from trait-based community assembly models based on macroinvertebrate body size, tolerance to anthropogenic disturbance, and fish-diet selectivity. The diet-selectivity model best fit the observed tailwater phylogenetic structure. Thus, apparent competition from subsidies phylogenetically structures prey communities, and serial variation in phylogenetic community structure can be indicative of fragmentation in formerly continuous ecosystems. " 2013 Springer-Verlag Berlin Heidelberg.",,,,,,"10.1007/s00442-013-2661-4",,,"http://hdl.handle.net/20.500.12104/44834","http://www.scopus.com/inward/record.url?eid=2-s2.0-84885914122&partnerID=40&md5=c8296562d019b1d2b04d61d06a393265",,,,,,"3",,"Oecologia",,"99

Depth-specific Variation in Carbon Isotopes Demonstrates Resource Partitioning Among the Littoral Zoobenthos

Benthic animals readily consume benthic algae, phytoplankton and terrestrial organic matter and are themselves a major component of fish diets. However, the effect of variation in resource availability on resource use by littoral macroinvertebrates remains poorly resolved. Using stable isotopes of carbon, we quantified depth-specific resource use by zoobenthic functional feeding groups in five lakes in northern Wisconsin. The littoral zoobenthos was collected from soft sediments at several depths in conjunction with samples of bulk periphyton (top 5 mm of sediment and biofilm) and measurements of benthic algal primary productivity. Periphyton δ13C was positively correlated with depth-specific benthic algal primary productivity, but grazer δ13C was consistently higher than that of the periphyton. The δ13C of infaunal collectors and predators was tightly correlated with, and nearly identical to, bulk periphyton δ13C (collectors: R2, 0.88; slope, 0.97; P \u3c 0.0001; predators: R2, 0.78; slope, 0.88; P \u3c 0.0001). Reliance of collectors and predators on benthic algal carbon varied between 43 and 100%, depending on whether grazers or bulk periphyton was used as the benthic algal end-member. Despite the apparent homogeneity of the sediments, benthic grazers and collectors partitioned resources in a consistent way in our study lakes, indicating either selective ingestion or assimilation of different components of the biofilm

Depth-specific Variation in Carbon Isotopes Demonstrates Resource Partitioning Among the Littoral Zoobenthos

Benthic animals readily consume benthic algae, phytoplankton and terrestrial organic matter and are themselves a major component of fish diets. However, the effect of variation in resource availability on resource use by littoral macroinvertebrates remains poorly resolved. Using stable isotopes of carbon, we quantified depth-specific resource use by zoobenthic functional feeding groups in five lakes in northern Wisconsin. The littoral zoobenthos was collected from soft sediments at several depths in conjunction with samples of bulk periphyton (top 5 mm of sediment and biofilm) and measurements of benthic algal primary productivity. Periphyton δ13C was positively correlated with depth-specific benthic algal primary productivity, but grazer δ13C was consistently higher than that of the periphyton. The δ13C of infaunal collectors and predators was tightly correlated with, and nearly identical to, bulk periphyton δ13C (collectors: R2, 0.88; slope, 0.97; P \u3c 0.0001; predators: R2, 0.78; slope, 0.88; P \u3c 0.0001). Reliance of collectors and predators on benthic algal carbon varied between 43 and 100%, depending on whether grazers or bulk periphyton was used as the benthic algal end-member. Despite the apparent homogeneity of the sediments, benthic grazers and collectors partitioned resources in a consistent way in our study lakes, indicating either selective ingestion or assimilation of different components of the biofilm