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To authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1600-0706.2009.17848.x Byline: Veronika Bokony, Anna Kulcsar, Andras Liker Abstract: How urbanization affects animal populations is in the focus of current ecological research. Existing theory of this topic suggests that the cities' more constant food supplies and lower predation pressure lead to a high proportion of weak competitors in urban populations. To evaluate this hypothesis, we tested whether competitive performance differs between differently urbanized populations of house sparrows Passer domesticus. We previously showed that wild urban sparrows are smaller and leaner than rural conspecifics, and this difference persists for months under identical captive conditions. Here we compared several aspects of their competitiveness (fighting, scrambling and searching for food) in captive mixed flocks of urban and rural birds. We found that sparrows exhibited consistent individual differences in competitiveness, but these differences were not related either to the degree of urbanization of their original habitats or to their body mass. Moreover, the variance in competitive abilities also did not differ between birds from more and less urbanized habitats. Thus our results did not support the hypothesis that urbanization shifts population structure towards an over-abundance of weak competitors in house sparrows. We discuss possible explanations why sparrow populations may not differ in competitiveness despite the smaller body mass of urban birds. Author Affiliation: (1) Dept of Limnology, Univ. of Pannonia, Pf. 158, HU-8201 Veszprem, Hungary (2) Dept of Ethology, Eotvos Univ., Pf. 120, HU-1518 Budapest, Hungary Article History: Paper manuscript accepted 28 July 2009 Article note: V. Bokony, Dept of Limnology, Univ. of Pannonia, Pf. 158, HU-8201 Veszprem, Hungary. E-mail: vbokony@enternet.hu

Understanding the various processes contributing to community assembly is among the central aims of ecology. As a means of exploring this topic we quantified the relative influences of habitat filtering and competition in establishing patterns of community functional trait diversity across a landscape of lakes. Habitat filtering has been invoked in shaping community structure when co-occurring taxa are more similar in their traits than expected by chance (under-dispersion), and competition has been inferred as a structuring agent when co-occurring taxa are less similar (over-dispersion). We tested these hypotheses in crustacean zooplankton communities using a functional trait-based approach based on five traits defining zooplankton feeding and habitat preferences across 51 lakes spanning several large limnological gradients. In general, zooplankton communities were functionally less diverse than random assemblages created from the same regional species pool. Furthermore, functional diversity was strongly correlated with variables related to lake productivity, suggesting that access to resources was the chief habitat filtering process constraining zooplankton functional diversity. This pattern was driven by the predominantly herbivorous cladocerans as opposed to the more commonly omnivorous, and sometimes carnivorous, copepods. [ABSTRACT FROM AUTHOR]

Human-induced processes are altering habitats at an unprecedented rate and scale. This has changed the biodiversity and biomass in many areas, but also led to phenotypic and genetic alterations of populations. Here we investigated the effects of the ongoing eutrophication in the Baltic Sea on the reproductive success of threespine stickleback males Gasterosteus aculeatus, through effects on reproductive behaviour and parenting ability. We allowed males to complete breeding cycles in a competitive setting under increased macro algae cover or increased turbidity caused by phytoplankton growth. Both environmental factors improved the parenting ability of the males and enhanced reproductive output. Increased alga growth and turbidity reduced aggressive interactions between males during the parental phase, probably due to reduced visibility, which slowed down a deterioration of condition. This increased the reproductive lifespan of the males and enabled them to complete more breeding cycles, as found when males were allowed to complete as many breeding cycles as they could under increased algae cover. In addition, increased turbidity improved oxygen conditions, which enhanced hatching success and reduced the need for vigorous fanning behaviour. Increased turbidity, however, relaxed selection on male size. Together with earlier results on relaxed sexual selection under changed environmental conditions, this suggests that the effect of eutrophication on stickleback populations is complex. It increases the reproductive output of populations, since more individuals are spawning within eutrophicated areas and their hatching success is increased, but it relaxes sexual and natural selection at the reproductive stage. Whether this will shift selection and population regulation to other life stages, such as the juvenile stage, deserves further investigations. [ABSTRACT FROM AUTHOR]

Two large food web data sets, each characterized by comprehensive sampling and high taxonomic resolution, display major differences in their structural properties. In 60 food webs compiled by Sugihara et al., representing such diverse habitats as springs, creeks, rotting logs, treeholes, and forest canopies, there is no significant increase in web complexity (SC) with species number (S), and predator/prey (PP)ratios average 2.2. The fractions of top (TF), intermediate (IF) andbasal (BF) species average 0.47, 0.35, and 0.18, respectively. Alonga gradient of increasing S, IF increases and BF declines. Maximal food chain length (MAX) also increases with S in the Sugihara webs, andaverages 2.7. In 50 food webs compiled by Havens, representing the pelagic communities of small lakes, SC increases rapidly with S, and PP averages only 0.6. Species fractions average 0.06 (TF), 0.44 (IF), and 0.50 (BF), and only IF is significantly correlated with S. MAX increases more rapidly with S than in the Sugihara webs, and it averages 4.7. Distinct properties of pelagic food webs, including high SC that increases rapidly with S, low PP, and high BF, are evidenced by the results of other studies, and may be due to (1) the predominance offilter-feeding predators that consume numerous prey taxa; and (2) tothe very high diversity of small particulate autotrophic prey species found in pelagic communities. [ABSTRACT FROM AUTHOR]

This sampler is intended to serve as an alternative to the Jenkin sampler and as a complement to the Ekman dredge. On principle it is a long open tube made of plexiglass. The cross-section is almost square. The sampler is submerged to the desired depth and pushed into the mud. It is immediately released and thin metal slides enter rapidly into the tube and divide it into separate chambers. The high speed of the closure makes it difficult even for very agile animals to move vertically to any appreciable extent. The stratification of the sediments in the sample is almost intact as has been proved by aquarium experiments Experiments in situ have been very successful. The sampler is intended for limnological as well as marine investigations of soft bottom sediments and of water strata close to the bottom. [ABSTRACT FROM AUTHOR]

The modern limnology has arisen from hydrobiology and it was recognized at last as a part of the general ecology or the science of the "household of Nature". The above account is in all essentials a story told in the first person singular, in which the author accounts for his own ideas. In 1882 S. A. Forbes designated the lake as a "microcosmos", in 1901 F. A. Forel called it an "Organ der Erde", but not until 1914 were these two basic principles in limnology amplified. "Lebensgemeinschaft" plus "Lebensraum" is considered a higher biological unit, because of the interplay between them. This modern view out of hydrobiology - the science which treats the life in the water - makes limnology, the science of the life of the fresh waters. The first thing to be done was, on the basis of the biological conditions governing the production, to divide the fresh waters, more particularly the lakes, into types. The fresh waters are, however, not an "autarc" microcosmos in the strictest sense of the word, but form part of the surroundings of which they depend. All biotopes depend on each other and form part of the great "Lebens- raum" of the earth. Thus the lake becomes a part of a constantly higher entity of the "Lebensraum". Limnology, therefore, becomes one of the three branches of the more comprehensive science which treats the household of Nature, i. e. the general ecology. The three ecological divisions on the earth, the terrestrial, limnic and marine, are so intimately connected that what happens in one of them can only be understood if conditions in the two others are also considered. Nature is one great entity. By stressing the entity in the interrelationships the [ABSTRACT FROM AUTHOR]