Search

In a recent paper, Young et al. (1994) proposed a graphical model indicating that under certain conditions (a dome-shaped functional response of the predator) prey swarming may entail not only benefits for the individual (Hamilton 1971), but also for the swarm as a whole (group level benefit). They argue that, in organisms that partially reproduce by apomictic parthenogenesis such as Daphnia, any grouprelated benefits may favour the formation of swarms among clone-mates. Young et al. (1994) then present field and laboratory observations on D. longispina that support the above notion, by showing that electrophoretically defined uniclonal populations often show a higher cohesion than multiclonal assemblages in a laboratory set-up, and that a swarm of D. longispina in a garden pond apparently mainly consisted of members of a single 'electrophoretic clone' (sensu Carvalho & Crisp 1987). The authors themselves point to the fact that this latter result needs to be interpreted with caution due to the fact that only one enzyme system (esterase), with an uncertain number of loci, was screened. We here present data that show for a population that coexists with fishes, where swarming is most probably a predator-avoidance strategy, that Daphnia swarms are no less genetically diverse than non-swarming individuals. The present data were collected during a survey of spatial genetic heterogeneity in Daphnia magna Straus populations, and in our opinion provide a more robust test of the above hypothesis than that presented by Young et al. (1994), since more samples (individuals and swarms/non-swarms) were analysed at four loci per individual. Our findings do not support the generality of kin-preferential swarming behaviour in Daphnia as a predator avoidance response.

Using a cloning technique, we revealed the existence of three phototactically distinct types in Daphnia magna, viz. negatives, positives, and “gipsies”. The latter migrate continuously between a low and a high light intensity. The expression of this behaviour is genetically determined, although positives and negatives can reversibly switch into “gipsies”.

Yeast cells produce various volatile metabolites that are key contributors to the pleasing fruity and flowery aroma of fermented beverages. Several of these fruity metabolites, including isoamyl acetate and ethyl acetate, are produced by a dedicated enzyme, the alcohol acetyl transferase Atf1. However, despite much research, the physiological role of acetate ester formation in yeast remains unknown. Using a combination of molecular biology, neurobiology, and behavioral tests, we demonstrate that deletion of ATF1 alters the olfactory response in the antennal lobe of fruit flies that feed on yeast cells. The flies are much less attracted to the mutant yeast cells, and this in turn results in reduced dispersal of the mutant yeast cells by the flies. Together, our results uncover the molecular details of an intriguing aroma-based communication and mutualism between microbes and their insect vectors. Similar mechanisms may exist in other microbes, including microbes on flowering plants and pathogens. publisher: Elsevier articletitle: The Fungal Aroma Gene ATF1 Promotes Dispersal of Yeast Cells through Insect Vectors journaltitle: Cell Reports articlelink: http://dx.doi.org/10.1016/j.celrep.2014.09.009 content_type: article copyright: Copyright © 2014 The Authors. Published by Elsevier Inc. ispartof: Cell Reports vol:9 issue:2 pages:425-432 ispartof: location:United States status: published

Tropical high Andes lakes are aquatic ecosystems with peculiar limnological characteristics that are related to their geographical location and high altitude, yet they remained understudied. We present the results of a standardized survey of morphometric, physico-chemical and biotic variables in 32 high altitude lakes of the Cordillera del Tunari (Eastern Andes of Bolivia). Based on the variables measured, we identified three lake types. One group of lakes differed from the other lakes by a relatively high pH and biological productivity (as evidenced from higher densities of phytoplankton, zooplankton, and fish). A second group of lakes consisted of relatively large and deep water bodies with neutral to slightly acid pH and with a relatively high occurrence of the large cladoceran Daphnia pulex . The third group contained relatively small, shallow, and acid lakes with no Daphnia . Rainbow trout occurred in more than half of the lakes and catch yields were very variable. Overall, the abundances of different organism groups tended to be positively associated (e.g. phytoplankton, copepods, rotifers, fish) indicating the existence of a major productivity gradient. We found no negative associations between trout catches and densities of any of the major zooplankton groups, suggesting moderate to low top-down effects of trout on the zooplankton communities.

In order to evaluate latitudinal differences in the relationship of phytoplankton biomass and diversity with environmental conditions in shallow lakes, we sampled 98 shallow lakes from three European regions: Denmark (DK), Belgium/The Netherlands (BNL) and southern Spain (SP). Phytoplankton biomass increased with total phosphorus (TP) concentrations and decreased with submerged macrophyte cover across the three regions. Generic richness was significantly negatively related to submerged macrophyte cover and related environmental variables. Zooplankton:phytoplankton biomass ratios were positively related to submerged macrophyte cover and negatively to phytoplankton generic richness in DK and BNL, suggesting that the low generic richness in lakes with submerged macrophytes was due to a higher zooplankton grazing pressure in these regions. In SP, phytoplankton generic richness was not influenced by zooplankton grazing pressure but related to conductivity. We observed no relationship between phytoplankton generic richness and TP concentration in any of the three regions. The three regions differed significantly with respect to mean local and regional generic richness, with BNL being more diverse than the other two regions. Our observations suggest that phytoplankton diversity in European shallow lakes is influenced by submerged macrophyte cover indirectly by modulating zooplankton grazing. This influence of submerged macrophytes and zooplankton grazing on phytoplankton diversity decreases from north to south.

The phototactic responses of four clones of Daphnia magna were experimentally analysed. Broad-sense heritability of this behavioural character was estimated through an analysis of variance, and it was very high under the standardised experimental conditions of this study.

Urbanization is changing Earth's ecosystems by altering the interactions and feedbacks between the fundamental ecological and evolutionary processes that maintain life. Humans in cities alter the eco-evolutionary play by simultaneously changing both the actors and the stage on which the eco-evolutionary play takes place. Urbanization modifies land surfaces, microclimates, habitat connectivity, ecological networks, food webs, species diversity, and species composition. These environmental changes can lead to changes in phenotypic, genetic, and cultural makeup of wild populations that have important consequences for ecosystem function and the essential services that nature provides to human society, such as nutrient cycling, pollination, seed dispersal, food production, and water and air purification. Understanding and monitoring urbanization-induced evolutionary changes is important to inform strategies to achieve sustainability. In the present article, we propose that understanding these dynamics requires rigorous characterization of urbanizing regions as rapidly evolving, tightly coupled human–natural systems. We explore how the emergent properties of urbanization affect eco-evolutionary dynamics across space and time. We identify five key urban drivers of change—habitat modification, connectivity, heterogeneity, novel disturbances, and biotic interactions—and highlight the direct consequences of urbanization-driven eco-evolutionary change for nature's contributions to people. Then, we explore five emerging complexities—landscape complexity, urban discontinuities, socio-ecological heterogeneity, cross-scale interactions, legacies and time lags—that need to be tackled in future research. We propose that the evolving metacommunity concept provides a powerful framework to study urban eco-evolutionary dynamics.

Cities are uniquely complex systems regulated by interactions and feedbacks between nature and human society. Characteristics of human society-including culture, economics, technology and politics-underlie social patterns and activity, creating a heterogeneous environment that can influence and be influenced by both ecological and evolutionary processes. Increasing research on urban ecology and evolutionary biology has coincided with growing interest in eco-evolutionary dynamics, which encompasses the interactions and reciprocal feedbacks between evolution and ecology. Research on both urban evolutionary biology and eco-evolutionary dynamics frequently focuses on contemporary evolution of species that have potentially substantial ecological-and even social-significance. Still, little work fully integrates urban evolutionary biology and eco-evolutionary dynamics, and rarely do researchers in either of these fields fully consider the role of human social patterns and processes. Because cities are fundamentally regulated by human activities, are inherently interconnected and are frequently undergoing social and economic transformation, they represent an opportunity for ecologists and evolutionary biologists to study urban "socio-eco-evolutionary dynamics." Through this new framework, we encourage researchers of urban ecology and evolution to fully integrate human social drivers and feedbacks to increase understanding and conservation of ecosystems, their functions and their contributions to people within and outside cities. ispartof: EVOLUTIONARY APPLICATIONS vol:14 issue:1 pages:248-267 ispartof: location:England status: published

As urbanization leads to repeated, marked environmental gradients in space, it provides an ideal ‘natural’ experiment to study how evolving metacommunities, in which evolutionary and community ecological processes interact in a landscape context, respond to anthropogenic disturbances. An integrated approach that combines community data with data on genetic responses of focal taxa to urbanization is still lacking, notwithstanding the likely importance of eco-evolutionary feedbacks on urban ecosystem functions and services. Such a joint analysis is most easily achieved by focusing on shifts in trait values and their interspecific (cf. community ecology) and intraspecific components. The latter involves both non-genetic and genetic responses, and should be quantified for all dominant, abundant, or ecologically important species in the (meta)community. This chapter introduces the evolving metacommunity framework and discusses the use of cities to study how this framework can contribute to our insight into population and community responses to anthropogenic change. It discusses how this framework can enhance our capacity to predict responses to contemporary and future urbanization as well as its possible consequences for ecosystem functioning. It predicts that evolutionary trait change contributes substantially to observed trait shifts at the community level. Conversely, genetic adaptation might often be constrained by rapid changes in species composition. It explores eco-evolutionary partitioning metrics that quantify the evolutionary and ecological contributions to responses to urbanization. Finally, it provides guidelines for experimental studies on urban evolving metacommunities, and suggests directions on research that will build towards a fully integrated evolving metacommunity framework addressing biological responses to urbanization.

Literature on local genetic differentiation in freshwater zooplankton populations is reviewed. The island-like nature of limnetic habitats creates opportunities for local genetic differentiation and adaptation to develop. There is a wealth of data available on genetic differentiation among populations of zooplankton with respect to allozyme markers. Data from welldesigned studies on ecologically relevant, quantitative traits are less abundant and indicate a different pattern from that obtained using electrophoretic markers. It is argued that whereas the analysis of (quasi) neutral markers emphasizes the importance of long-lasting founder effects and genetic drift, the pattern of local genetic differentiation of ecologically relevant traits may often reflect local adaptation. In reviewing the data, the importance of temporal and spatial habitat selection in maintaining genetic polymorphism for ecologically relevant traits is emphasized, without denying the importance of stochasticity. Most availab...

The field of eco-evolutionary dynamics is developing rapidly, with a growing number of well-designed experiments quantifying the impact of evolution on ecological processes and patterns, ranging from population demography to community composition and ecosystem functioning. The key challenge remains to transfer the insights of these proof-of-principle experiments to natural settings, where multiple species interact and the dynamics are far more complex than those studied in most experiments. Here, we discuss potential pitfalls of building a framework on eco-evolutionary dynamics that is based on data on single species studied in isolation from interspecific interactions, which can lead to both under- and overestimation of the impact of evolution on ecological processes. Underestimation of evolution-driven ecological changes could occur in a single-species approach when the focal species is involved in co-evolutionary dynamics, whereas overestimation might occur due to increased rates of evolution following ecological release of the focal species. In order to develop a multi-species perspective on eco-evolutionary dynamics, we discuss the need for a broad-sense definition of “eco-evolutionary feedbacks” that includes any reciprocal interaction between ecological and evolutionary processes, next to a narrow-sense definition that refers to interactions that directly feed back on the interactor that evolves. We discuss the challenges and opportunities of using more natural settings in eco-evolutionary studies by gradually adding complexity: (a) multiple interacting species within a guild, (b) food web interactions and (c) evolving metacommunities in multiple habitat patches in a landscape. A literature survey indicated that only a few studies on microbial systems so far developed a truly multi-species approach in their analysis of eco-evolutionary dynamics, and mostly so in artificially constructed communities. Finally, we provide a road map of methods to study eco-evolutionary dynamics in more natural settings. Eco-evolutionary studies involving multiple species are necessarily demanding and might require intensive collaboration among research teams, but are highly needed.

Microparasites and epibionts have important implications for the ecology and evolution of their zooplankton host populations. Many parasites and epibionts produce resistant spores that infect new hosts upon intake. We explored the hypothesis that these spores build up dormant stage banks that remain infective for several years (decades). In laboratory experiments, we exposed Daphnia magna to sediments taken from different depths in sediment cores from four different shallow water bodies. All samples analyzed contained infective stages of epibionts, suggesting that dormant stage banks remain infective for decades. Microparasite infections from old sediments were only obtained in one of the four ponds studied. We found mainly the bacterium Pasteuria ramosa but also a yet undescribed microsporidium. We discuss the implications of long-lasting spore banks for the disease dynamics and coevolution in the Daphnia-microparasite system. ispartof: Limnology and oceanography vol:49 issue:4 pages:1355-1364 status: published

DIEL vertical migration (DVM) of zooplankton is generally considered to be a predator-avoidance strategy: zooplankton migrate to greater depths during the day to reduce their chance of being detected by visual predators (fish)(1). Both phenotypic plasticity and interpopulational genetic variability in DVM patterns exist in zooplankton(2,3). We used large indoor mesocosms ('plankton towers'(4)) to study intrapopulational genetic variation for day depth in a Daphnia hyalina x galeata hybrid population. Clones differing in body size also differed in vertical distribution, with the largest clone residing at the greatest depth during the day. A selection experiment in the presence of fish indicates that alternative antipredator strategies, which involve a complex association between habitat-selection traits and life-history strategies, might be an important factor underlying intrapopulational genetic polymorphism in zooplankton, through a balancing of fitness effects in the presence of visual predators. ispartof: Nature vol:378 issue:6556 pages:483-485 status: published

We tested the relative importance of regional and local factors in determining zooplankton community composition in an enclosure experiment. In this experiment, we assessed establishment success of immigrant cladoceran zooplankton species in young communities in the first and second year of existence in five newly created pools. In both years, we created four treatments, representing a gradient of strength in biotic interactions with the resident communities, to explore differences in establishment success of immigrant species. In general, species diversity increased when immigrant species were added, suggesting dispersal limitation. However, this increase was lower in the second than in the first year, indicating a declining effect of regional factors during the course of community assembly. No significant difference in establishment success between the experimental treatments could be detected in the first year. In the second year, immigrant species were more often present in the treatment without resident species than in the treatments with resident species, at least during the first weeks. Our results demonstrate that species sorting and biotic interactions, mainly competition among zooplankton species and predation by Chaoborus, become important in determining the zooplankton community composition early in community assembly.

We carried out a laboratory study to evaluate the sensitivity of phototactic behavior of Daphnia magna to sublethal concentrations of pentachlorophenol (PCP) and copper. More specifically, we determined whether the sensitivity of a D. magna clone to those pollutants is influenced by food quality and the presence of fish kairomones. Test animals were fed either unicellular green algae (Scenedesmus acutus) or fresh baker's yeast (Saccharomyces cerevisiae) and were cultured in the presence or absence of fish kairomones. Four concentrations of PCP (0.4, 0.8, 1.2, and 1.6 mg/L PCP) and one concentration of copper (0.02 mg/L Cu2+) in International Standards Organisation (ISO, Geneva, Switzerland) standard medium were applied in the experiments. Animals were exposed for 3 h to the pollutants prior to the experiments. In the absence of fish kairomones, a strong negative relationship between the phototactic index and nominal sublethal concentrations of PCP was found in animals fed either algae or yeast. The sensitivity of the Daphnia clone to sublethal concentrations of PCP was, however, less clear cut in animals fed yeast than in animals fed algae. The detection limit was 0.4 mg/L PCP with algae as food but was as high as 1.2 mg/L PCP when yeast was used as food. The ability to detect sublethal concentrations of copper and PCP using phototactic behavior was lost when the clones were cultured in the presence of fish kairomones. At a concentration of 0.02 mg/L Cu2+ and in the absence of fish kairomones, the D. magna clone tested became significantly less positively phototactic than in the control treatment regardless of the quality of the food used to culture the test animals. These results suggest that assays using the phototactic behavior of Daphnia to monitor water quality should use genetically stable (clonal) material, positively phototactic, and insensitive to the presence of fish kairomones.

We studied the relative roles of environmental species sorting and priority effects in the assembly of ecological communities on long time scales, by analyzing community turnover of water fleas (Daphnia) in response to strong and recurrent environmental change in a fluctuating tropical lake. During the past 1800 years, Lake Naivasha (Kenya) repeatedly fluctuated between a small saline pond habitat during lowstands and a large freshwater lake habitat during highstands. Starting from a paleoecological reconstruction, we estimated the role of priority effects in Daphnia community assembly across 16 of these habitat turnovers and compared this with the response of the community to reconstructed changes in three environmental variables important for species sorting. Our results indicate that the best predictor of Daphnia community composition during highstands was the community composition just prior to the transition from lowstands to highstands. This reflects a long-lasting priority effect of late lowstand communities on highstand communities, arising when remnant lowstand populations fill newly available ecological space in the rapidly expanding lake habitat. Species sorting and priority effects had a comparable but relatively small influence on community composition during the lowstands. Moreover, these priority effects decayed rapidly with time as Daphnia communities responded to environmental change, in contrast with the highstand communities where priority effects lasted for several decades. Key words: community assembly, Daphnia spp, Lake Naivasha, Kenya, mass effect, metacommunity, niche, paleoecology, priority effect, propagule pressure, restoration ecology, storage effect ispartof: Ecology vol:92 issue:12 pages:2267-2275 ispartof: location:United States status: published

Organisms are often confronted with multiple enemy species. Defenses against different parasite species may be traded off against each other. However, if resistance is based on (potentially costly) general defense mechanisms, it may be positively correlated among parasites. In an experimental study, we confronted 19 clones from one Daphnia magna population with two bacterial and three microsporidian parasite species. All parasites were isolated from the same pond as the hosts. Host clones were specific in their susceptibility towards different parasite species, and parasite species were host-clone specific in their infectivity, spore production, and virulence, resulting in highly significant host-parasite interactions. Since the Daphnia's resistance to different parasite species showed no obvious correlation, neither general defense mechanisms nor trade-offs in resistance explain our findings. None of the Daphnia clones were resistant to all parasite species, and the average level of resistance was quite similar among clones. This may reflect a cost of defense, so that the cumulative cost of being resistant to all parasite species might be too high. ispartof: Evolution vol:57 issue:4 pages:784-792 ispartof: location:United States status: published