Kin-biased distribution in brown trout: an effect of redd location or kin recognition?

A wide range of animals have been reported to show kin-biased behaviours, such as reduced aggressiveness and increased food sharing among relatives. However, less is known about whether wild animals also associate with relatives under natural conditions, which is a prerequisite to facilitate kin-biased behaviours and hence kin selection. We tested, by means of microsatellite polymorphism, correlations between pair-wise relatedness and pair-wise metric distance in wild brown trout (Salmo trutta L.) under natural conditions in two streams. Our data show that young-of-the-year as well as older trout found close together also had a higher genetic relatedness in one of the two streams, whereas no relationship was found in the other stream. Very few half and full siblings were found in the second stream and under these conditions it is unlikely that kin-biased behaviours will receive positive selection. We discuss the underlying mechanisms for the observed structure and we specifically address the issue of whether the grouping of related individuals could reflect dispersal from the same spawning redds, or if it reflects active association with relatives, possibly conferring kin-selected advantages.     

Microgeographic variation in metabolic rate and energy storage of brown trout: countergradient selection or thermal sensitivity?

We examined the influence of habitat size, growth opportunity, and the thermal conditions experienced during early development on the standard metabolic rate (SMR) of juvenile brown trout (Salmo trutta) from six natural populations to contrast the hypothesis of countergradient selection in metabolic rate. The study populations differed significantly in SMR. Population means for SMR changed in response to the temperature experienced during the yolk-absorption stage, when the risk of oxygen deficit increases and the vulnerability to hypoxia is highest. We also found a strong negative correlation between the temperature experienced during the first 2 months after yolk resorption and SMR, which supports the hypothesis of countergradient variation. Moreover, we detected a strong negative correlation between an index of growth opportunity and relative lipid content, suggesting that the risk of energy shortfall could be a major force in the evolution of storage strategies. Our results suggest that temperature can shape the evolution of metabolic rate during the yolk-absorptive stage or the first feeding stage, while energy storage levels may be more sensitive to thermal constraints acting on growth rates.     

Palaeolimnological study of an environmental monitoring area,or, are there pristine lakes in Finland?

A palaeolimnological study of Lake Iso-Hietajärvi in Patvinsuo National Park, Lieksa, East Finland was conducted. The drainage area of the lake is one of four Integrated Monitoring areas established in Finland. Lead-210 dating reveals a period of increased sedimentation in the lake from 1920 to 1950. Increased atmospheric burden of several heavy metals in the order Pb > Cu> Zn > Ti = Al > Cr = Ni = V is recorded. The first to expand during the 19th century is Pb, whilst V increases after 1950. Sedimentary chlorophyll derivatives expand in the early part of the 20th century. Assemblages of diatoms and Cladocera were also changed somewhat during this time, but water quality seems not to have varied much: e.g. the diatom-inferred pH has remained in the range 6.4–6.8 (with a slight decrease) throughout the period of study.     

Adaptation to environmental stress: a rare or frequent driver of speciation?

Recent results of evolutionary genomics and other research programmes indicate an important role for environment-dependent selection in speciation, but the conceptual frameworks of speciation genetics and environmental stress physiology have not been fully integrated. Only a small number of model systems have been established for cross-disciplinary studies of this type in animals and plants. In these taxa (e.g. Drosophila and Arabidopsis/Arabis), studies of the mechanistic basis of various stress responses are increasingly combined with attempts to understand their evolutionary consequences. Our understanding of the role of environmental stress in speciation would benefit from studies of a larger variety of taxa. We pinpoint areas for future study and predict that in many taxa 'broad' hybrid zones maintained by ecological selection will be valuable venues for addressing the link between environmental stress, adaptation, and speciation.     

Is there genetic variation in the response to competition intensity in juvenile brown trout Salmo trutta?

Effects of intraspecific competition intensities on the relative performance (growth and movement) of juvenile brown trout Salmo trutta originating from nine different families were tested in tank experiments and in semi-natural streams. Both growth and movement differed consistently among families, indicating genetic variation in these traits. There were no significant interaction effects, however, between the intensity of competition and family origin on performance in either of the two experimental systems. Thus, genetic variation in response to competition intensity appeared to be limited in the population from which the juveniles used in this experiment originate.     

Is there a threshold size regulating seaward migration of brown trout and Atlantic salmon?

We investigated the influence of variation in body size and growth rate on age of smolting in Atlantic salmon and brown trout in four different Norwegian rivers. In Atlantic salmon smolt ages varied between 2 and 6 years, and in brown trout between 2 and 7 years. Smolt age was negatively correlated with parr growth, and positively correlated with smolt size. Age at smolting was more variable in the two northern than the two southern rivers. Smolt sizes and ages were also more variable in brown trout than in Atlantic salmon. Based on the observed variation in smolt size and age, we reject the hypothesis that a threshold size alone regulates age at smolting. Within populations smolt age depends on growth rate so that fast-growing parr smolted younger and smaller than slow-growing parr. We hypothesize that smolt size and age is a trade-off between expected benefits and costs imposed by differences in individual growth rate.     

Using energetic budgets to assess the effects of environmental stress on corals: are we measuring the right things?

Historically, the response of marine invertebrates to their environment, and environmentally induced stress, has included some measurement of their physiology or metabolism. Eventually, this approach developed into comparative energetics and the construction of energetic budgets. More recently, coral reefs, and scleractinian corals in particular, have suffered significant declines due to climate change-related environmental stress. In addition to a number of physiological, biophysical and molecular measurements to assess “coral health,” there has been increased use of energetic approaches that have included the measurement of specific biochemical constituents (i.e., lipid concentrations) as a proxy for energy available to assess the potential outcomes of environmental stress on corals. In reading these studies, there appears to be some confusion between energy budgets and carbon budgets. Additionally, many assumptions regarding proximate biochemical composition, metabolic fuel preferences and metabolic quotients have been made, all of which are essential to construct accurate energy budgets and to convert elemental composition (i.e., carbon) to energy equivalents. Additionally, models of energetics such as the metabolic theory of ecology or dynamic energy budgets are being applied to coral physiology and include several assumptions that are not appropriate for scleractinian corals. As we assess the independent and interactive effects of multiple stressors on corals, efforts to construct quantitative energetic budgets should be a priority component of realistic multifactor experiments that would then improve the use of models as predictors of outcomes related to the effects of environmental change on corals.     

The costs of being male: are there sex-specific effects of uniparental mitochondrial inheritance?

Eukaryotic cells typically contain numerous mitochondria, each with multiple copies of their own genome, the mtDNA. Uniparental transmission of mitochondria, usually via the mother, prevents the mixing of mtDNA from different individuals. While on the one hand, this should resolve the potential for selection for fast-replicating mtDNA variants that reduce organismal fitness, maternal inheritance will, in theory, come with another set of problems that are specifically relevant to males. Maternal inheritance implies that the mitochondrial genome is never transmitted through males, and thus selection can target only the mtDNA sequence when carried by females. A consequence is that mtDNA mutations that confer male-biased phenotypic expression will be prone to evade selection, and accumulate. Here, we review the evidence from the ecological, evolutionary and medical literature for male specificity of mtDNA mutations affecting fertility, health and ageing. While such effects have been discovered experimentally in the laboratory, their relevance to natural populations—including the human population—remains unclear. We suggest that the existence of male expression-biased mtDNA mutations is likely to be a broad phenomenon, but that these mutations remain cryptic owing to the presence of counter-adapted nuclear compensatory modifier mutations, which offset their deleterious effects.     

Genic heterozygosity, chromosomal interchanges and fitness in rye: any relationship?

Relationship between heterozygosity at allozyme loci, chromosomal interchanges and fitness was analyzed in a rye cultivar showing a polymorphism for such rearrangements. Nine allozyme systems (ACO, ACPH, GOT, GPI, LAP, MDH, PER, PGD and PGM) and five components of fitness (number of fertile tillers, total offspring, egg cell fertility, flowers/ear and seeds/ear) were studied. The estimated selection coefficients against interchange heterozygotes ranged from s = 0.12 to s = 0.34. A significant effect of the genic heterozygosity on some fitness components was observed in interchange heterozygotes (tillering and total offspring), in their standard homozygous sibs (flowers/ear and seeds/ear) and in the descendants of the crosses between standard karyotypes (flowers/ear, seeds/ear and egg cell fertility). However, the main effect was linked to genetic background associated to different crosses. Significant differences for Acph-1, Gpi-1, Lap-1, Mdh-1, Mdh-4, Pgd-2 and Pgm-1 loci were also found in some of these crosses although these differences were inconsistent. This suggests that probably the allozyme loci analyzed were not directly contributing to the fitness and that they are linked, in some cases, to different deleterious alleles depending on both cross and locus. This fact could support the local effect hypothesis as explanation although we do not discard the existence of some inbreeding level (general effect hypothesis) since all crosses and loci studied show a overall consistent trend of increased fitness with increased heterozygosity.     

Variation in growth and age at maturity in bluegill sunfish: genetic or environmental effects?

Populations of bluegill sunfish Lepomis macrochirus , experiencing heavy juvenile predation, showed increased growth rates and increased age and size at maturity relative to populations experiencing decreased predation on juveniles but increased predation on adults. This study examined bluegills experimentally from both types of populations and a cross between them in a common environment to determine if variation in growth and age at maturity is genetically or environmentally induced. Two factorial experiments, varying strain of bluegills and resource availability, were used to evaluate differences in growth rate. One experiment, varying strain of bluegills, was used to assess differences in age at maturity. Growth was strongly influenced by resource level, but growth rate did not vary among populations. Nearly all bluegills in each population matured at 1 year of age in a common environment. Thus, variation observed in source populations must be mostly attributable to differences in the environment between populations. At least three factors could potentially cause differences in growth and age at maturity: (1) variation in resource availability; (2) variation in demographic structure; and (3) variation in size-specific mortality rates caused by differences in predator abundance between populations. Observed patterns of variation between populations are best explained by effects of differences in predator populations.     

Phylogenetic distribution of catalase-peroxidases: are there patches of order in chaos?

Hydrogen peroxide features in many biological oxidative processes and must be continuously degraded enzymatically either via a catalatic or a peroxidatic mechanism. For this purpose ancestral bacteria evolved a battery of different heme and non-heme enzymes, among which heme-containing catalase-peroxidases (CP) are one of the most widespread representatives. They are unique since they can follow both H(2)O(2)-degrading mechanisms, the catalase activity being clearly dominant. With the fast increasing amount of genomic data available, we were able to perform an extensive search for CP and found almost 300 sequences covering a large range of microorganisms. Most of them were encoded by bacterial genomes, but we could also find some in eukaryotic organisms other than fungi, which has never been shown until now. Our screen also reveals that approximately 60% of the bacteria do not possess CP genes. Chaotic distribution among species and incongruous phylogenetic reconstruction indicated existence of numerous lateral gene transfers in addition to duplication events and regular speciation. The results obtained show an impressively complex gene transmission pattern, and give some new insights about the role of CP and the origin of life on earth. Finally, we propose for the first time bacterial candidates that may have participated in the transfer of CP from bacteria to eukaryotes.     

Endocrine responses to unpredictable environmental events: stress or anti-stress hormones?

In addition to seasonal changes in morphology, physiology andbehavior that occur in predictable annual cycles, there arefacultative responses to unpredictable events known as labile(i.e., short-lived) perturbation factors (LPFs). These rapidbehavioral and physiological changes have been termed the "emergency"life history stage (ELHS) and serve to enhance life-time fitness.Glucocorticosteroids interacting with other hormones in thehypothalamo-pituitary-adrenal (HPA) cascade, initiate and orchestratethe ELHS within minutes to hours. Components of the ELHS include:redirection of behavior from a normal life history stage toincreased foraging, irruptive-type migration during the day,enhanced restfulness at night, elevated gluconeogenesis andrecovery once the perturbation passes. These physiological andbehavioral changes allow an individual to avoid potential deleteriouseffects of stress that may result from chronically elevatedlevels of circulating glucocorticosteroids over days and weeks.In other words, acute rises in glucocorticosteroids followingperturbations of the environment may actually avoid chronicstress and serve primarily as "anti-stress" hormones. Severalfield studies in diverse habitats indicate that free-livingpopulations have elevated circulating levels of corticosteroidswhen in an ELHS. However, expression of an ELHS may not alwaysbe advantageous and there is accumulating evidence from birdsthat the adrenocortical responses to LPFs are modulated bothon seasonal and individual levels. These data suggest that glucocorticosteroidsecretions in response to LPFs not only trigger physiologicaland behavioral responses but also allow flexibility so thatthe response is integrated in relation to time of year (normalLHS) as well as individual differences owing to body condition,disease and social status.     

Detail in network models of epidemiology: are we there yet?

Network models of infectious disease epidemiology can potentially provide insight into how to tailor control strategies for specific regions, but only if the network adequately reflects the structure of the region's contact network. Typically, the network is produced by models that incorporate details about human interactions. Each detail added renders the models more complicated and more difficult to calibrate, but also more faithful to the actual contact network structure. We propose a statistical test to determine when sufficient detail has been added to the models and demonstrate its application to the models used to create a synthetic population and contact network for the USA.     

Induction of phlorotannin production in a brown alga: defense or resource dynamics?

Increase of phenolic secondary metabolites, phlorotannins, in brown algae due to gastropod grazing has been interpreted as an anti-herbivore adaptation. Here we tested whether such a response could be due to changes in truly available resources for the alga, not by the grazing activity of snails as such. We allowed two species of snails, Theodoxus fluviatilis and Physa fontinalis to graze on Fucus vesiculosus . These species feed on epibiota and particulate matter on the thallus but do not eat the thallus of F. vesiculosus . We further simulated snail grazing by nutrient enhancement, removal of epibiota and by a combination of the two. Manipulations of nutrient and light availability revealed the crucial role of epibiota in mediating resource availability for F. vesiculosus . Nutrient enhancement alone increased epibiota and decreased phlorotannins. Cleaning the thallus resulted in increased growth, and together with nutrient enhancement also in a trade-off with phlorotannins. Presence of T. fluviatilis on the thallus induced phlorotannin production, a response differing from the simulations of snail grazing. However, we suggest that the increase in phlorotannins may not be an induced defense but rather a consequence of a specific way of resource manipulation by this snail species. T. fluviatilis removes hyaline hairs that facilitate nutrient uptake. P. fontinalis did not remove hyaline hairs and the response of the alga to its grazing was similar to the treatment where we mechanically removed epibiota suggesting that cleaning of the thallus is the major mechanism how this snail species affects F. vesiculosus . Genetic variation in phlorotannin concentrations highly exceeded the induced responses of simulated or real snail grazing. This casts doubt for the efficiency of induced phlorotannin production to act as a defense, but is not contradictory with the interpretation of phlorotannins responding to variation in resource availability.     

Spatial patterns of woody plant and bird diversity: functional relationships or environmental effects?

Aim To understand cross‐taxon spatial congruence patterns of bird and woody plant species richness. In particular, to test the relative roles of functional relationships between birds and woody plants, and the direct and indirect environmental effects on broad‐scale species richness of both groups. Location Kenya. Methods Based on comprehensive range maps of all birds and woody plants (native species > 2.5 m in height) in Kenya, we mapped species richness of both groups. We distinguished species richness of four different avian frugivore guilds (obligate, partial, opportunistic and non‐frugivores) and fleshy‐fruited and non‐fleshy‐fruited woody plants. We used structural equation modelling and spatial regressions to test for effects of functional relationships (resource–consumer interactions and vegetation structural complexity) and environment (climate and habitat heterogeneity) on the richness patterns. Results Path analyses suggested that bird and woody plant species richness are linked via functional relationships, probably driven by vegetation structural complexity rather than trophic interactions. Bird species richness was determined in our models by both environmental variables and the functional relationships with woody plants. Direct environmental effects on woody plant richness differed from those on bird richness, and different avian consumer guilds showed distinct responses to climatic factors when woody plant species richness was included in path models. Main conclusions Our results imply that bird and woody plant diversity are linked at this scale via vegetation structural complexity, and that environmental factors differ in their direct effects on plants and avian trophic guilds. We conclude that climatic factors influence broad‐scale tropical bird species richness in large part indirectly, via effects on plants, rather than only directly as often assumed. This could have important implications for future predictions of animal species richness in response to climate change.     

Has the introduction of brown trout altered disease patterns in native New Zealand fish?

1. It is well recognised that non-indigenous species (NIS) can affect native communities via the 'spillover' of introduced parasites. However, two other potentially important processes, the 'spillback' of native parasites from a competent NIS host, where the latter acts as a reservoir leading to amplified infection in native hosts, and the 'dilution' of parasitism by a NIS host acting as a sink for native parasites, have either not been tested or largely overlooked.
2. We surveyed the helminth parasite fauna of native New Zealand fish in Otago streams that varied in the abundance of introduced brown trout Salmo trutta , to look for evidence of spillback and/or dilution. Spillover is not an issue in this system, with trout introduced as parasite-free eggs.
3. Seven native parasite species were present across 12 sites; significant inverse relationships with an index of trout abundance (i.e. dilution) were documented for three species infecting the native upland bully Gobiomorphus breviceps , and one species infecting the native roundhead galaxias Galaxias anomalus .
4. An inverse relationship between bully energy status and infection intensity of one parasite species suggests that parasite dilution could have positive effects on bully populations. Our failure to detect similar relationships for the other parasites does not preclude the possibility that dilution is beneficial to native fish, since parasites may have subtle or unmeasured impacts.
5. The parasite dilution patterns reported are compelling in that they occurred across several native host and parasite species; as such they have important implications for invasion ecology, providing an interesting contrast to the largely negative impacts reported for NIS. Mechanisms potentially responsible for the patterns observed are discussed.     

DNA and buffers: are there any noninteracting, neutral pH buffers?

The interaction of DNA with various neutral pH, amine-based buffers has been analyzed by free solution capillary electrophoresis, using a mixture of a plasmid-sized DNA molecule and a small DNA oligonucleotide as the reporter system. The two DNAs migrate as separate, nearly Gaussian-shaped peaks in 20-80 mM TAE (TAE, Tris-acetate-EDTA; Tris, tris[hydroxymethyl]aminomethane) buffer. The separation between the peaks gradually increases with increasing TAE buffer concentration because of differences in solvent friction between large and small DNA molecules. The two DNAs form complexes with the borate ions in TBE (Tris-borate-EDTA) buffer, with mobilities that depend on the DNA/borate ratio. In 45 mM TBE buffer, the two DNAs comigrate as a single sharp peak, with a mobility that is faster than either of the constituent DNAs in the same buffer. Hence, the mixed DNA-borate complex is stabilized by the binding of additional borate ions, possibly forming bridges between the different DNAs. The mixed DNA-borate complex is gradually dissociated into its component DNAs by increasing the TBE concentration, possibly because the borate binding sites become saturated at high buffer concentrations. Other neutral pH, amine-based buffers, such as Mops (3-[N-morpholino]propanesulfonic acid), Hepes (N-[2-hydroxyethyl]piperazine-N'-[2-ethanesulfonic acid]), Bes (N,N-bis[2-hydroxyethyl]-2-aminoethanesulfonic acid), Tes (N-tris[hydroxymethyl]methyl-2-aminoethanesulfonic acid), and tricine (N-tris[hydroxymethyl]methylglycine) also form complexes with DNA, giving distorted peaks in the electropherograms. The combined results indicate that borate buffers and most neutral pH, amine-based buffers interact with DNA.