Predators have a key role shaping competitor dynamics in food webs. Perhaps the most obvious way this occurs is when predators reduce competitor densities. However, consumption could also generate phenotypic selection on prey that determines the strength of competition, thus coupling consumptive and trait-based effects of predators. In a mesocosm experiment simulating fish predation on damselflies, we found that selection against high damselfly activity ratesa phenotype mediating predation and competitionweakened the strength of density dependence in damselfly growth rates. A field experiment corroborated this finding and showed that increasing damselfly densities in lakes with high fish densities had limited effects on damselfly growth rates but generated a precipitous growth rate decline where fish densities were lowera pattern expected because of spatial variation in selection imposed by predation. These results suggest that accounting for both consumption and selection is necessary to determine how predators regulate prey competitive interactions.

No abstract

Recent increases of animal mass mortality events have coincided with substantial changes in global climate. Yet, tractable approaches that predict how climate change will accentuate occurrences of these ecological catastrophes remain nascent. We compiled one of the most comprehensive datasets of lentic fish mortality events, thermal tolerances of affected families, and 1.2 million air and water temperature profiles across 8891 north temperate lakes in North America. Temperature extremes within and across lakes were strongly associated with the three most frequent cause types (infectious agents, summerkills, winterkills). Thermal tolerances mediated the lethality of direct thermal stress, but mortalities of warm‐ and cold‐water fishes occurred at similar temperature deviations. Water and air temperature‐based models accurately predicted contemporary summerkills and suggested ~ 6‐ to 34‐fold increases, respectively, in their frequency by 2100. These models forecast and contextualize impending ecosystem changes in an increasingly volatile world.

The Red-bellied Snake (Storeria occipitomaculata) primarily inhabits moist woodlands of eastern North America, with two disjunct populations occurring in the Great Plains, one of which is in south-central Nebraska. This species is listed as at-risk in Nebraska, in part, due to being uncommon with limited information available about the ecology and natural history of this isolated population. We amassed 48 observations of Red-bellied Snakes in Nebraska from museum specimens and published accounts, including our observations and others reported to us published herein. The previous earliest documented date of spring emergence was 6 April from a specimen collected in 1999. On 12 March 2016, we observed an adult Red-bellied Snake along the Platte River in Buffalo County, Nebraska, which predates the previous earliest documented emergence date by almost a month. It is unclear whether our observation represents an unusual behavior related to an unseasonably warm winter or a normal occurrence that has remained undocumented for this secretive, uncommon snake. Our summary of observations in Nebraska demonstrates Red-bellied Snakes are active March through October, with peaks in observations in April/May and September. This disjunct population occurs within the Big Bend Reach of the Platte River in south-central Nebraska, which is a major spring stopover site for migratory Sandhill Cranes (Antigone canadensis). Emergence in March by these snakes greatly increases predation risks by opportunistically foraging cranes. Additional ecological information is warranted for this disjunct population, as use of the Platte River flood plains by Sandhill Cranes has increased during the last half century, and removal of riparian forests has been a common habitat management practice for Sandhill Cranes and endangered Whooping Cranes (Grus americana).

No abstract