Declines in occurrence of plants characteristic for a nutrient‐poor meadow habitat are partly explained by their responses to nutrient addition and competition

Species losses and local extinctions are alarmingly common, frequently as a consequence of habitat destruction. Nevertheless, many intact habitats also face species losses, most likely due to environmental changes. However, the exact drivers, and why they affect some species more than others in apparently intact habitats, are still poorly understood. Addressing these questions requires data on changes in occurrence frequency of many species, and comparisons of the responses of those species to experimental manipulations of the environment. Here, we use historic (1911) and contemporary (2017) data on the presence–absence of 42 plant species in 14 seemingly intact Molinia meadows around Lower Lake Constance to quantify changes in occurrence frequency. Then, we performed a common-garden experiment to test whether occurrence frequencies in 1911 and changes therein by 2017 could be explained by responses of the 42 species to nutrient addition and competition with the acquisitive generalist grass Poa pratensis. Within the 14 still intact Molinia meadows, 36 of the 42 species had declined since 1911. As expected, nutrient addition generally led to increased biomass production of the 42 target species, and competition with P. pratensis had a negative effect. The latter was stronger at high nutrient availability. The more frequent species were in 1911 and the more they declined in frequency between 1911 and 2017, the less above-ground biomass they produced in our experiment. Competition with P. pratensis magnified this effect. Our work highlights that environmental change can contribute to local extinction of species in otherwise intact habitat remnants. Specifically, we showed that increased nutrient availability negatively affected formerly widespread Molinia-meadow species in competition with P. pratensis. Our study thus identified a likely mechanism for the decline in occurrence frequency of species in the remaining Molinia meadows.publishe

Ump1p Is Required for Proper Maturation of the 20S Proteasome and Becomes Its Substrate upon Completion of the Assembly

We report the discovery of a short-lived chaperone that is required for the correct maturation of the eukaryotic 20S proteasome and is destroyed at a specific stage of the assembly process. The S. cerevisiae Ump1p protein is a component of proteasome precursor complexes containing unprocessed β subunits but is not detected in the mature 20S proteasome. Upon the association of two precursor complexes, Ump1p is encased and is rapidly degraded after the proteolytic sites in the interior of the nascent proteasome are activated. Cells lacking Ump1p exhibit a lack of coordination between the processing of β subunits and proteasome assembly, resulting in functionally impaired proteasomes. We also show that the propeptide of the Pre2p/Doa3p β subunit is required for Ump1p's function in proteasome maturation

Response of fish species to river restoration -the role of species traits

Abstract 21 Species are known to respond differently to restoration efforts, but we still lack a clear 22 conceptual understanding of these differences. We analyzed the development of an entire fish 23 community as well as the relationship between multi-metric response patterns of fish species 24 and their ecological species traits at a comprehensively monitored river restoration project, the 25 Lippe River in Germany. Using electrofishing data from 21 consecutive years (4 years pre-26 and 17 years post-restoration) from multiple restored and unrestored control reaches, we 27 demonstrated that this restoration fully reached its targets, approximately doubling both 28 species richness and abundance. Species richness continuously increased while fish density 29 exhibited an overshooting response in the first years post restoration. Both richness and 30 abundances stabilized approximately seven years after the restoration, although interannual 31 variability remained considerable. The response of each species to the restoration was 32 characterized using a set of six parameters. Relating the dissimilarity in species response to 33 their ecological dissimilarity, based on 13 species traits, we found life-history and 34 reproduction-related traits were the most important for species' responses to restoration. 35 Short-lived species with early female maturity and multiple spawning runs per year exhibited 36 the strongest response, reflecting the ability of fast reproducers to rapidly colonize new 37 habitats. Fusiform-bodied species also responded more positively than deep-bodied species, 38 reflecting the success of this restoration to reform appropriate hydromorphological conditions 39 (riffles and shallow bays), for which these species depend. Our results demonstrate that 40 repeated sampling over periods longer than seven years are necessary to reliably assess river 41 restoration outcomes. Furthermore, this study emphasizes the utility of species traits for 42 examining restoration outcomes, particularly the metapopulation and metacommunity 43 processes driving recovery dynamics. Focusing on species traits instead of species identity 44 also allows for easier transfer of knowledge to other biogeographic areas and promotes 45 coupling to functional ecology. 46 PeerJ Preprints | https://doi.org/10.7287/peerj.preprints.2173v1 | CC BY 4.0 Open Access