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Lake and stream fauna are frequently studied, yet surprisingly little is known about ecological and evolutionary dynamics of species that inhabit both lentic and lotic habitats. There are few examples of species co-occurring in different flow types, which raises questions about how co-occurrence may influence ability to adapt to changing climatic conditions. One such co-occurring species is the aquatic insect Limnephilus externus Hagen, 1861 (Trichoptera:Limnephilidae), a species known to be widely distributed in lakes of the Nearctic and Palearctic regions. Here, we test whether lake–stream populations of the caddisfly L. externus are evolutionarily or ecologically distinct. We examined larval body and case morphology, interspecies phoretic associations, and the mitochondrial DNA cytochrome c oxidase I gene among lake and stream populations of L. externus. We also explored potential morphological differences among distinct haplotypes. We observed differences between lake and stream populations in abundance, phenology, some aspects of body and case morphology, and abdominal mite presence, indicating that lakes and streams may yield distinct ecological phenotypes for this species. We also observed distinct regional differences in caddisfly body condition and case construction sturdiness and found distinct assemblages of microinvertebrates associated with the caddisfly's body and cases. Lake–stream L. externus did not show genetic divergence; however, 3 potentially distinct haplotypes were present across the research sites as well as in sequences from North America and Canada. Limnephilus externus appears to exhibit wide geographic range and low geographic sequence structure, which could account for the species' large variation in phenology and morphology at the lake–stream level. Combined life history and phylogenetic studies provide valuable insight into the ecological and evolutionary dynamics that influence the adaptability of aquatic fauna to climatic change. [ABSTRACT FROM AUTHOR]

Efforts to explain animal population cycles often invoke consumer-resource theory, which has shown that consumer-resource interactions alone can drive population cycles. Eco-evo theory instead argues that population cycles are partly driven by fluctuating selection for resistance in the resource, but support for eco-evo theory has come almost entirely from laboratory microcosms. Here we ask, Can eco-evo theory explain population cycles in the field? We compared the ability of eco-evo models and classical "eco-only" models to explain data on cycles in the insect Lymantria dispar , in which outbreaks of the insect are terminated by a fatal baculovirus. We carried out a statistical comparison of the ability of eco-only and eco-evo models to explain combined data from L. dispar outbreak cycles and baculovirus epizootics (epidemics in animals). Both models require high host variation in resistance to explain the epizootic data, but high host variation in the eco-evo model leads to consistently accurate predictions of outbreak cycles, whereas in the presence of high host variation the eco-only model can explain outbreak cycles only by invoking high levels of stochasticity, which leads to highly variable and often inaccurate predictions of outbreak cycles. Our work provides statistically robust evidence that eco-evo models can explain population cycles in the field. [ABSTRACT FROM AUTHOR]

The distribution of biodiversity depends on the combined and interactive effects of ecological and evolutionary processes. The joint contribution of these processes has focused almost exclusively on deterministic effects, even though mechanisms that increase the importance of random ecological processes are expected to also increase the importance of random evolutionary processes. Here we manipulate the sizes of old field fragments to generate correlated sampling effects for a focal population (a gall maker) and its enemy community. Traits and communities were more variable in smaller patches. However, because of the preference of some enemies for some trait values (gall sizes), random variation in population mean trait values exacerbated differences in community composition. The random distribution of traits and interactions created predictable but highly variable patterns of natural selection. Our study highlights how stochastic processes can affect ecological and evolutionary processes structuring the strength and direction of selection locally and at larger scales. [ABSTRACT FROM AUTHOR]

Species do not live, interact, or evolve in isolation but are instead members of complex ecological communities. In ecological terms, complex multispecies interactions can be understood by considering indirect effects that are mediated by changes in traits and abundances of intermediate species. Interestingly, traits and abundances are also central to our understanding of phenotypic selection, suggesting that indirect effects may be extended to understand evolution in complex communities. Here we explore indirect ecological effects and their evolutionary corollary in a well-understood food web comprising a plant, its herbivores, and enemies that select for opposite defensive phenotypes in one of the herbivores. We show that ecological indirect interactions are mediated by changes to both the traits and the abundances of intermediate species and that these changes ultimately reduce enemy attack and weaken selection. We discuss the generality of the link between indirect effects and selection. We go on to argue that local adaptation and eco-evolutionary feedback may be less likely in complex multispecies food webs than in simpler food chains (e.g., coevolution). Overall, considering selection in complex interaction networks can facilitate the rapprochement of community ecology and evolution. [ABSTRACT FROM AUTHOR]

For many taxa and systems, species richness peaks at mid-elevations. One potential explanation for this pattern is that large-scale changes in climate and geography have, over evolutionary time, selected for traits that are favored under conditions found in contemporary midelevation regions. To test this hypothesis, we use records of historical temperature and topographic changes over the past 65 Myr to construct a general simulation model of plethodontid salamander evolution in eastern North America. We then explore possible mechanisms constraining species to midelevation bands by using the model to predict plethodontid evolutionary history and contemporary geographic distributions. Our results show that models that incorporate both temperature and topographic changes are better able to predict these patterns, suggesting that both processes may have played an important role in driving plethodontid evolution in the region. Additionally, our model (whose annotated source code is included as a supplement) represents a proof of concept to encourage future work that takes advantage of recent advances in computing power to combine models of ecology, evolution, and earth history to better explain the abundance and distribution of species over time. [ABSTRACT FROM AUTHOR]