Male cognitive performance declines in the absence of sexual selection

Sexual selection is responsible for the evolution of male ornaments and armaments, but its role in the evolution of cognition—the ability to process, retain and use information—is largely unexplored. Because successful courtship is likely to involve processing information in complex, competitive sexual environments, we hypothesized that sexual selection contributes to the evolution and maintenance of cognitive abilities in males. To test this, we removed mate choice and mate competition from experimental populations of Drosophila melanogaster by enforcing monogamy for over 100 generations. Males evolved under monogamy became less proficient than polygamous control males at relatively complex cognitive tasks. When faced with one receptive and several unreceptive females, polygamous males quickly focused on receptive females, whereas monogamous males continued to direct substantial courtship effort towards unreceptive females. As a result, monogamous males were less successful in this complex setting, despite being as quick to mate as their polygamous counterparts with only one receptive female. This diminished ability to use past information was not limited to the courtship context: monogamous males (but not females) also showed reduced aversive olfactory learning ability. Our results provide direct experimental evidence that the intensity of sexual selection is an important factor in the evolution of male cognitive ability.     

Effects of quaternary ammonium salts on membrane potential and electric conductance in internodal cells of Nitettopsis obtusa

Effects of amphiphilic derivatives of glycine esters of the general formula (CH₃)₃N⁺CH₂COOC_nH_2n+1Cl- (n = 10, 12, 14, 16) on membrane potential and conductance in internodal cells of the alga Nitellopsis obtusa were studied. The compounds decreased the potential difference between vacuole and external medium and increased the electric conductance. The effects depended on the length of the alkyl chain (n) and the concentration of these quaternary ammonium salts. Light-induced hyperpolarization was suppressed by the salts. We suggest that the ammonium salts inhibit the electrogenic proton pump in the plasmalemma and enhance the passive efflux of Cl- from the algal cell.     

Pex19 is involved in importing dually targeted tail‐anchored proteins to both mitochondria and peroxisomes

Tail‐anchored (TA) proteins are embedded into their corresponding membrane via a single transmembrane segment at their C‐terminus whereas the majority of the protein is facing the cytosol. So far, cellular factors that mediate the integration of such proteins into the mitochondrial outer membrane were not found. Using budding yeast as a model system, we identified the cytosolic Hsp70 chaperone Ssa1 and the peroxisome import factor Pex19 as import mediators for a subset of mitochondrial TA proteins. Accordingly, deletion of PEX19 results in: (1) growth defect under respiration conditions, (2) alteration in mitochondrial morphology, (3) reduced steady‐state levels of the mitochondrial TA proteins Fis1 and Gem1, and (4) hampered in organello import of the TA proteins Fis1 and Gem1. Furthermore, recombinant Pex19 can bind directly the TA proteins Fis1 and Gem1. Collectively, this work identified the first factors that are involved in the biogenesis of mitochondrial TA proteins and uncovered an unexpected function of Pex19.      

Effects of removal and regeneration of bankside vegetation on fish population dynamics in the Warta River,Poland

In March 1989 both banks of a 450 m section of the Warta River, 2 km above a reservoir, were cleared of their riparian vegetation (osiers, willows and alders). In October 1988 17 fish species had been recorded there, with a standing crop (SC) of 31.9 kg ha ^–1. In April 1989, the number of species decreased to 11, and their SC to 7.9 kg ha ^–1.Over the next three years new alder trees appeared and osiers regrew to 3.5 m. The SC in October 1990, October 1991 and May 1992 was recorded at 36.5, 66.2 and 40.9 kg ha ^–1, respectively. The primary effect was on phytophils, whose biomass was directly proportional to the height of the trees and osiers (r = 0.87, p = 0.05). The litho-phytophils appeared to occupy the habitat vacated by the phytophils soon after bank clearance (r = –0.87, p = 0.05), but then declined as the osiers grew.     

Interaction of melanin with carbon- and oxygen-centered radicals from methanol and ethanol

The interaction of dopa-melanin (DM) and cysteinyldopa-melanin (CDM) with carbon- and oxygen-centered radicals generated by benzophenone-photosensitized hydrogen abstraction from ethanol, or by pulse radiolysis of aqueous solutions of methanol and ethanol, is reported. Photosensitized formation of carbon-centered radicals and their interaction with melanin was monitored by electron paramagnetic resonance (EPR) spin trapping using DMPO, and via the melanin free radical signal itself. In the pulse radiolysis experiments, the interaction of DM or CDM with hydroxymethyl, hydroxyethyl, and the corresponding methanol peroxyl radical was monitored by recording time-dependent changes of the melanin absorbance at selected wavelengths. The data indicate that both melanins are good scavengers of carbon-centered radicals, with corresponding rate constants in the range of 10⁷ to 10⁸ M⁻¹ s⁻¹. Significantly, compared to DM, CDM is also an exceptionally efficient scavenger of oxygen-centered radicals derived from methanol with corresponding rate constants of 2.7 × 10⁴ and 2 × 10⁶, M⁻¹ s⁻¹ for DM and CDM, respectively. The results are discussed with reference to the potential role of melanin in protecting the integrity of melanosomes by inhibiting peroxidation of lipid components of the organelle membrane.     

The structure and dynamics of old-growth Pinus sylvestris (L.) stands in the Wigry National Park,north-eastern Poland

The paper describes the structure and the developmental trends of old-growth Pinus sylvestris stands in the Wigry National Park, in north-eastern Poland. The stands represent a transitional zone between deciduous forests of Central Europe and boreal, coniferous forests of north-eastern Europe. Besides P. sylvestris, the most important tree species are Picea abies and Quercus robur. Among the subcanopy species, Corylus avellana and Sorbus aucuparia occur most frequently. On the basis of the data from 6 permanent sample plots (total size: 1.90 ha), several parameters and stand indices are analysed including species composition of the canopy and the regeneration, diameter distribution, age structure of main tree species, and the relationship between canopy and spatial dispersion of woody regeneration. The most striking feature of the stands studied is the almost complete absence of natural regeneration of P. sylvestris. This seems to be in contradiction with the apparently natural origin of this species in the stands, and a common occurrence of natural disturbances resulting in openings and gaps in forest canopy. The main tree species replacing P. sylvestris in the canopy are P. abies and Q. robur. Also increasing are some broad-leaved species typical of high fertility sites: Acer platanoides, Tilia cordata, Ulmus glabra, and Fraxinus excelsior. A shrub C. avellana occurs extensively competing with tree species and delaying tree replacement processes. While no direct data on the changes in the site conditions can be provided and the recovery hypothesis appears to be the most straightforward explanation of the changes in P. sylvestris stands, the possible role of the allogenic changes in environmental conditions (climate warming, nitrogen deposition) is also discussed.     

Novel inhibitors of influenza sialidases related to GG167 structure-activity, crystallographic and Molecular dynamics studies with 4H-pyran-2-carboxylic acid 6-carboxamides

The structure-activity relationships of a series of 4-amino and guanidino-4H-pyran-2-carboxylic acid 6-carboxamides are described. These compounds represent a new class of inhibitor of influenza sialidases and are particularly active against influenza A sialidase. The binding of the N-phenethyl-N-propylamide 41 to influenza A and B sialidases has been investigated using X-ray crystallography and molecular dynamics simulations. Our results suggest that formation of a hitherto unobserved intramolecular salt bridge within the enzymes may account for the observed activity and selectivity of the series.     

Disentangling natural and anthropogenic drivers of changes in a shallow lake using palaeolimnology and historical archives

Shallow lakes are susceptible to catastrophic regime shifts characterised by the presence or absence or macrophytes. However, the long-term controls on macrophyte succession in shallow lakes are incompletely understood. To investigate this, we analysed multiple sediment proxies in Lake Rotcze (Eastern Poland), a small, shallow and densely macrophyte-covered lake to (1) reconstruct the ‘reference conditions’ (sensu WFD) and development of the lake in recent centuries, (2) compare historical evidence with the sedimentary record, and (3) identify the natural and anthropogenic drivers of macrophyte succession. Before the twentieth century, conditions in the lake may be referred to as ‘reference conditions’. Subsequently forest clearance in the catchment resulted in lower water transparency, but concurrent catchment drainage lowered water levels and increased macrophyte development. Since 1950 elevated nutrient supply and climatically driven increases in water levels led to the deterioration of water transparency and partial macrophyte withdrawal. At the end of the twentieth century lake-level drawdown led to low phytoplankton biomass and clear water creating a novel ecosystem where macrophytes invade the whole lake. These patterns suggest that both natural and anthropogenically induced water level fluctuations have been critical drivers of macrophyte development.