TY - JOUR A1 - Ceulemans, Ruben A1 - Guill, Christian A1 - Gaedke, Ursula T1 - Top predators govern multitrophic diversity effects in tritrophic food webs JF - Ecology : a publication of the Ecological Society of America N2 - It is well known that functional diversity strongly affects ecosystem functioning. However, even in rather simple model communities consisting of only two or, at best, three trophic levels, the relationship between multitrophic functional diversity and ecosystem functioning appears difficult to generalize, because of its high contextuality. In this study, we considered several differently structured tritrophic food webs, in which the amount of functional diversity was varied independently on each trophic level. To achieve generalizable results, largely independent of parametrization, we examined the outcomes of 128,000 parameter combinations sampled from ecologically plausible intervals, with each tested for 200 randomly sampled initial conditions. Analysis of our data was done by training a random forest model. This method enables the identification of complex patterns in the data through partial dependence graphs, and the comparison of the relative influence of model parameters, including the degree of diversity, on food-web properties. We found that bottom-up and top-down effects cascade simultaneously throughout the food web, intimately linking the effects of functional diversity of any trophic level to the amount of diversity of other trophic levels, which may explain the difficulty in unifying results from previous studies. Strikingly, only with high diversity throughout the whole food web, different interactions synergize to ensure efficient exploitation of the available nutrients and efficient biomass transfer to higher trophic levels, ultimately leading to a high biomass and production on the top level. The temporal variation of biomass showed a more complex pattern with increasing multitrophic diversity: while the system initially became less variable, eventually the temporal variation rose again because of the increasingly complex dynamical patterns. Importantly, top predator diversity and food-web parameters affecting the top trophic level were of highest importance to determine the biomass and temporal variability of any trophic level. Overall, our study reveals that the mechanisms by which diversity influences ecosystem functioning are affected by every part of the food web, hampering the extrapolation of insights from simple monotrophic or bitrophic systems to complex natural food webs. KW - food-web efficiency KW - functional diversity KW - machine learning KW - nutrient KW - exploitation KW - production KW - random forest KW - temporal variability KW - top KW - predator KW - trait diversity Y1 - 2021 U6 - https://doi.org/10.1002/ecy.3379 SN - 0012-9658 SN - 1939-9170 VL - 102 IS - 7 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Eccard, Jana A1 - Liesenjohann, Thilo A1 - Dammhahn, Melanie T1 - Among-individual differences in foraging modulate resource exploitation under perceived predation risk JF - Oecologia N2 - Foraging is risky and involves balancing the benefits of resource acquisition with costs of predation. Optimal foraging theory predicts where, when and how long to forage in a given spatiotemporal distribution of risks and resources. However, significant variation in foraging behaviour and resource exploitation remain unexplained. Using single foragers in artificial landscapes of perceived risks and resources with diminishing returns, we aimed to test whether foraging behaviour and resource exploitation are adjusted to risk level, vary with risk during different components of foraging, and (co)vary among individuals. We quantified foraging behaviour and resource exploitation for 21 common voles (Microtus arvalis). By manipulating ground cover, we created simple landscapes of two food patches varying in perceived risk during feeding in a patch and/or while travelling between patches. Foraging of individuals was variable and adjusted to risk level and type. High risk during feeding reduced feeding duration and food consumption more strongly than risk while travelling. Risk during travelling modified the risk effects of feeding for changes between patches and resulting evenness of resource exploitation. Across risk conditions individuals differed consistently in when and how long they exploited resources and exposed themselves to risk. These among-individual differences in foraging behaviour were associated with consistent patterns of resource exploitation. Thus, different strategies in foraging-under-risk ultimately lead to unequal payoffs and might affect lower trophic levels in food webs. Inter-individual differences in foraging behaviour, i.e. foraging personalities, are an integral part of foraging behaviour and need to be fully integrated into optimal foraging theory. KW - animal personality KW - giving-up density KW - intra-specific trait variation KW - landscape of fear KW - optimal foraging KW - predation risk KW - resource KW - exploitation Y1 - 2020 U6 - https://doi.org/10.1007/s00442-020-04773-y SN - 0029-8549 SN - 1432-1939 VL - 194 IS - 4 SP - 621 EP - 634 PB - Springer CY - Berlin ER - TY - JOUR A1 - Marfo, Charles A1 - Yeboah, Philomena Abeka A1 - Bonku, Lucy T1 - Exploiting the exploiter: some violations of society's expectations in beyond the horizon and the housemaid JF - 3 L : language, linguistics, literature ; the Southeast Asian journal of English language studies N2 - This paper does a critical reading of Beyond the Horizon and The Housemaid and observes that the author, Amma Darko, seeks primarily to challenge prevailing and traditional views of motherhood held by African societies; i.e. motherhood and its associated activities such as caring, training and disciplining. Amma Darko sharply condemns this view and calls for a critical analysis of the nature of motherhood, especially in contemporary times. Agreeing with Amma Darko and taking issues raised by her even a little further, with snippets from the books, the paper brings to the fore the fact that the prevailing and traditional views of motherhood have inherent conflict with reality. That is to say, these views are carelessly assumed as problem-free. Within this context, we also critically bring into discussion the running theme of exploiting the exploiter in the two books within the framework of gender studies and queer theory. We also generally question the fixed categories of paradigms generated by normative ideology and conclude with the realisation that almost all mothers (and, for that matter, exhibition of womanhood) in these novels failed because of the wrong choices they made, which were basically and largely fuelled by challenging economic conditions. KW - culture KW - exploitation KW - gender KW - motherhood KW - traditional expectations Y1 - 2015 SN - 0128-5157 VL - 21 IS - 1 SP - 35 EP - 46 PB - School of Language Studies & Linguistics, Universiti Kebangsaan Malaysia CY - Bangi ER -