Clone-specific responses in leaf phenolics of willows exposed to enhanced UVB radiation and drought stress

The effects of enhanced UVB radiation and drought stress on willow secondary phenolics were studied using the leaves of 8‐week‐old micropropagated plantlets from interspecific hybrids (Salix myrsinites L. ×S. myrsinifolia Salisb.) and pure species (S. myrsinifolia). The plantlets were subjected for 4 weeks to two levels of UVB radiation (ambient, enhanced) and two levels of watering (well‐watered, drought‐stressed) according to a 2 × 2 factorial design. Enhanced UVB radiation increased the total concentration of flavonoids and phenolic acids in all plantlets, while the total concentration of salicylates remained unaffected. Drought stress reduced the total concentration of salicylates and phenolic acids in S. myrsinifolia plantlets, while in hybrids only phenolic acids were affected. The response of phenolic acids to enhanced UVB in drought‐stressed plantlets was different from that in well‐watered ones, indicating that drought stress limited the accumulation of phenolic acids under enhanced UVB radiation. Flavonoids increased in response to enhanced UVB radiation in drought‐stressed plantlets, although drought caused serious physiological stress on growth. There were significant differences between hybrid and S. myrsinifolia plantlets with respect to the composition of phenolics and between families and clones with respect to their concentration. In addition, the response of salicylates, flavonoids and phenolic acids to enhanced UVB and drought stress was clone‐specific, which may indicate that climatic changes will alter the genetic composition of northern forests.     

The role of niche breadth, resource availability and range position on the life history of butterflies

We analysed the relationship between three life history characteristics (mobility, length of flight period and body size) and niche breadth (larval host plant specificity and adult habitat breadth), resource availability (distribution and abundance of host plants) and range position (distance between the northernmost distribution record and southernmost point of Finland) of the butterfly fauna of Finland. The data is based on literature and questionnaires. Often in across species studies phylogeny may create spurious relationships between life-history and ecological variables. We took the phylogenetic relatedness of butterfly species into account by analysing the data with phylogenetically independent contrasts (CAIC method). Butterfly mobility was positively related to the niche breadth, resource availability and range position. The length of the flight period was negatively related to the range position, indicating that the species at the northern edge of their distribution range have shorter flight period than species which are further way from the range edge. After controlling for the phylogenetic relatedness we found no significant correlations between body size and niche breadth, resource availability or range position. We suggest that the relationship between the length of the flight period and range position may arise as a consequence of lower hatching asynchrony in edge species as a result of lower environmental variance in larval growth conditions. Our results on the mobility suggest that there is selection pressure towards lower migration rate in species that have restricted niche breadth, low resource availability and in species that are on the northern edge of their geographical distribution range. In such species, selection against mobile individuals is likely to result from the decreased probability of finding another habitat patch suitable for egg laying.     

Responses of growth and phlorotannins in <Emphasis Type="Italic">Fucus vesiculosus</Emphasis> to nutrient enrichment and herbivory

Discharge from anthropogenic sources may modify both macroalgal growth patterns and resource allocation to carbon based secondary compounds, thereby affecting their susceptibility for herbivory. We tested the effect of eutrophication in terms of nutrient enhancement on growth and phlorotannin concentration of Fucus vesiculosus by conducting manipulative experiments in the field and mesocosms. In the field experiment we utilised fish farms as nutrient sources and in the mesocosm-experiment we manipulated ambient nutrient levels and occurrence of the herbivorous isopod Idotea baltica. Vicinity of a fish farm affected neither growth nor the phlorotannin concentration of Fucus but increased the amount of epiphytes growing on Fucus. Other organisms such as epiphytic filamentous algae and periphyton, which are more capable of quickly utilizing excess nutrients, may restrain the direct effects of nutrient enhancement on Fucus. In a manipulative mesocosm experiment, neither nutrient enrichment nor occurrence of herbivores affected phlorotannin concentration implying lack of induced defences, at least in terms of increasing phlorotannin concentration. Feeding of thallus decreased the growth rate of algae, but the number of reproductive organs, receptacles, was not affected by herbivory. The negative effect of herbivory on the amount of apical tips tended to be stronger under nutrient enriched conditions. We conclude that eutrophication processes, in terms of nutrient enrichment, does not have strong direct effect on growth or phlorotannin production of F. vesiculosus. However, there may be important indirect consequences. First, herbivory may be targeted more to apical parts of the thallus under eutrophicated conditions. Second, the result that Fucus growing close to nutrient sources were smaller than those in control areas may reflect differences in mortality schedules of algae between eutrophicated and control areas.     

Genotypic variation in tolerance and resistance to fouling in the brown alga <Emphasis Type="Italic">Fucus vesiculosus</Emphasis>

In this study, we examined genetic variation in resistance and tolerance to fouling organisms in the brown alga Fucus vesiculosus. We first grew 30 algal genotypes in the field, where we allowed fouling organisms to colonise the genotypes at natural levels. We then conducted a manipulative experiment, where we grew 20 genotypes of algae in aquaria with or without fouling organisms. We measured host resistance as the load of fouling organisms and tolerance as the slope of the regression of algal performance on fouling level. Fouling organisms decreased host growth and contents of phlorotannins and thus have the potential to act as selective agents on algal defenses. We found significant among-genotype variation in both resistance and tolerance to fouling. We did not find a trade-off between resistance and tolerance. We found a marginally significant cost of resistance, but no cost of tolerance. Our results thus indicate that both the tolerance and resistance of F. vesiculosus can evolve as a response to fouling and that the costs of resistance may maintain genetic variation in resistance.     

Mate-search efficiency can determine the evolution of separate sexes and the stability of hermaphroditism in animals

Limited availability of mating partners has been proposed as an explanation for the occurrence of simultaneous hermaphroditism in animals with pair mating. When low population density or low mobility of a species limits the number of potential mates, simultaneous hermaphrodites may have a selective advantage because, first, they are able to adjust the allocation of resources between male and female functions in order to maximize fitness; second, in a hermaphroditic population the likelihood of meeting a partner is higher because all individuals are potential mates; and, third, in the absence of mating partners, many simultaneously hermaphroditic animals have the option of reproducing through self-fertilization. Recognizing that mate availability is central to the existing theory of hermaphroditism in animals, it is important to examine the effects of mate search on predictions of the stability of hermaphroditism. Many hermaphroditic animals can increase the number of potential mates they contact by active searching. However, since mate search has costs in terms of time and energy, the increased number of potential mates will be traded off against the amount of resources that can be allocated to the production of gametes. We explore the consequences of this trade-off to the evolution of mating strategies and to the selective advantage of self-fertilization. We show that in low and moderate population densities, poor mate-search efficiency and high costs of searching stabilize hermaphroditism and bias sex allocation toward female function. In addition, in very low population densities, there is strong selective advantage for self-fertilization, but this advantage decreases considerably in species with high mate-search efficiency. Most important, however, we present a novel evolutionary prediction: when mate search is efficient, disruptive frequency-dependent selection on time allocation to mate search leads to the evolution of searching and nonsearching phenotypes and, ultimately, to the evolution of males and females.     

Bottom-up and cascading top-down control of macroalgae along a depth gradient

On marine rocky shores, macroalgal herbivory is often intense, such that the cascading effects of fish predation may contribute to the control of algal communities. To estimate the magnitudes of top-down and bottom-up control on a macroalgal community, we manipulated the access of carnivorous fish to macroalgal colonization substrates, as well as nutrient availability, at two sub-littoral depths. There were three levels of fish manipulation: natural fish community, no fish and the enclosure of one common species, the perch, Perca fluviatilis. We found a clear cascade effect of fish predation on both the total density and several individual species of macroalgae, which was more pronounced in deep than shallow water. The density of the dominant grazers, i.e. snails, increased in nutrient-enriched conditions; perch were inefficient in controlling herbivores, and had therefore no cascading effect on algal densities under such conditions. Although nutrients enhanced the growth of opportunistic algae, herbivores, in the absence of fish, inhibited this response. While algal diversity was higher in shallow than in deep water, the enrichment effect was opposite at the two depths with lowered diversity in the shallows and increased at depth. Our results indicate that fish predation is an efficient regulator of meso-herbivores and that its effect thereby cascades onto the producer trophic level such that both perennial and opportunistic algae benefit from the presence of fish. This cascade effect is probably stronger at depth where predation efficiency is less disturbed by wave motion.     

Analysis of a 2,4,6-trichlorophenol-dehalogenating enrichment culture and isolation of the dehalogenating member Desulfitobacterium frappieri strain TCP-A

An anaerobic, 2,4,6-trichlorophenol ortho-dehalogenating mixed culture was enriched from sediment of the river Saale (Germany). Two isolated dechlorinating colonies (MK1 and MK2) consisted of rods of different lengths and thicknesses, indicating heterogeneity. Following subcultivation with thiosulfate as alternative electron acceptor and cocultivation with Clostridium celerecrescensT, the 2,4,6-trichlorophenol-dehalogenating bacterium Desulfitobacterium frappieri strain TCP-A was isolated and characterized regarding its taxonomic properties and the spectrum of chlorophenols that it dehalogenated. Four other bacterial strains were coenriched and identified as organisms with closest phylogenetic relatedness to the Clostridium type strains C. indolis, C. glycolicum, C. hydroxybenzoicum and C. sporosphaeroides (16S rDNA sequence identities of 99.5, 99.2, 94.4, and 93.5%, respectively). Amplified ribosomal DNA restriction analysis of the original dehalogenating cultures MK1 and MK2 (when not exposed to thiosulfate) confirmed the microbial heterogeneity and revealed the presence of two additional species related to the type strains of C. celerecrescens and Clostridium propionicum. Only one copy of the 16S rRNA genes of Desulfitobacterium frappieri in each of the clone libraries of MK1 and MK2 (containing 136 and 56 clones, respectively) was found by dot-blot hybridization, suggesting a relatively low number of the dehalogenating bacterium within the enrichment culture.     

Dynamics of Canadian lynx populations in space and time1

The records of Canadian lynx fur returns indicate rather regular self-repeating pattern with 9–11 yr cycles That the lynx populations over a vast geographical range fluctuate in synchrony appears to be well established The finding that the degree of synchrony levels off with increasing distance among provinces compared to increase again between the furthest–away provinces (O–shape) has largely escaped notice in previous analyses Moreover, the pattern of synchrony against distance varies depending on the period of time used m the analysis, sometimes there is O–shape, sometimes mere negative correlation, and sometimes no relationship whatsoever The entire rich pattern of lynx dynamics in space and time can be emulated by sets of local subpopulations acknowledging dispersal among populations This all suggest that local dynamics of populations cannot be fully understood unless the significance of spatial linkage of subpopulations via dispersal of individuals is acknowledged     

GABA-benzodiazepine receptor complex and drug actions

This short review describes the benzodiazepine receptors, their interplay with GABAergic transmission and chloride ionophore, the search for endogenous ligands, and the drug responses that can be evoked through these receptors. Benzodiazepine receptors offer a unique pathway through which opposite drug actions e.g., anxiogenic and anxiolytic effects can be exerted, and these actions can be inhibited with competitive receptor antagonists. The most plausible endogenous ligand for benzodiazepine receptors discovered so far, a polypeptide DBI, exerts actions opposite to those of the benzodiazepines used in clinical therapy. This has been the stimulus for a new look at the physiological role for these receptors.