A quantitative review of heterozygosity–fitness correlations in animal populations

The ease of obtaining genotypic data from wild populations has renewed interest in the relationship between individual genetic diversity and fitness-related traits (heterozygosity–fitness correlations, or HFC). Here we present a comprehensive meta-analysis of HFC studies using powerful multivariate techniques which account for nonindependence of data. We compare these findings with those from univariate techniques, and test the influence of a range of factors hypothesized to influence the strength of HFCs. We found small but significantly positive effect sizes for life-history, morphological, and physiological traits; while theory predicts higher mean effect sizes for life-history traits, effect size did not differ consistently with trait type. Newly proposed measures of variation were no more powerful at detecting relationships than multilocus heterozygosity, and populations predicted to have elevated inbreeding variance did not exhibit higher mean effect sizes. Finally, we found evidence for publication bias, with studies reporting weak, nonsignificant effects being under-represented in the literature. In general, our review shows that HFC studies do not generally reveal patterns predicted by population genetic theory, and are of small effect (less than 1% of the variance in phenotypic characters explained). Future studies should use more genetic marker data and utilize sampling designs that shed more light on the biological mechanisms that may modulate the strength of association, for example by contrasting the strength of HFCs in mainland and island populations of the same species, investigating the role of environmental stress, or by considering how selection has shaped the traits under investigation.     

Increased temperature sensitivity of net DOC production from ombrotrophic peat due to water table draw-down

The production and release of dissolved organic carbon (DOC) from peat soils is thought to be sensitive to changes in climate, specifically changes in temperature and rainfall. However, little is known about the actual rates of net DOC production in response to temperature and water table draw‐down, particularly in comparison to carbon dioxide (CO₂) fluxes. To explore these relationships, we carried out a laboratory experiment on intact peat soil cores under controlled temperature and water table conditions to determine the impact and interaction of each of these climatic factors on net DOC production. We found a significant interaction (P < 0.001) between temperature, water table draw‐down and net DOC production across the whole soil core (0 to −55 cm depth). This corresponded to an increase in the Q₁₀ (i.e. rise in the rate of net DOC production over a 10 °C range) from 1.84 under high water tables and anaerobic conditions to 3.53 under water table draw‐down and aerobic conditions between −10 and − 40 cm depth. However, increases in net DOC production were only seen after water tables recovered to the surface as secondary changes in soil water chemistry driven by sulphur redox reactions decreased DOC solubility, and therefore DOC concentrations, during periods of water table draw‐down. Furthermore, net microbial consumption of DOC was also apparent at − 1 cm depth and was an additional cause of declining DOC concentrations during dry periods. Therefore, although increased temperature and decreased rainfall could have a significant effect on net DOC release from peatlands, these climatic effects could be masked by other factors controlling the biological consumption of DOC in addition to soil water chemistry and DOC solubility. These findings highlight both the sensitivity of DOC release from ombrotrophic peat to episodic changes in water table draw‐down, and the need to disentangle complex and interacting controls on DOC dynamics to fully understand the impact of environmental change on this system.     

Gall morpho-type corresponds to separate species of gall-inducing thrips (Thysanoptera: Phlaeothripidae)

Kladothrips rugosus Froggatt has previously been considered a single polyphagous species that, in Australia, induces galls on several species of Acacia , with the gall structure varying both within and between hosts. On Acacia papyrocarpa , two types of gall are induced by this species, one with the surface ridged but the other with the surface smooth. Using sequence data from cytochrome oxidase subunit I (CO I ) and elongation factor-1 alpha gene fragments, we show that the thrips inducing these two gall-types are genetically distinct and comprise separate lineages. Uncorrected ' p ' distances calculated from CO I gene fragments were 0.000 and 0.006 within lineages and 0.074 and 0.078 between lineages. The between-lineage distances are comparable with distances between morphologically distinct species of other Acacia gall-thrips. Re-examination of adult thrips from the two gall types revealed consistent differences in body colour, as well as in body sculpture. Together with observations on gall founding behaviour, these data indicate that the thrips populations in the two gall types on A. papyrocarpa are reproductively isolated and should be considered as separate species. The form from smooth galls on A. papyrocarpa is therefore described as Kladothrips nicolsoni sp. nov. , although the form from ridged galls can be considered only as ' K. rugosus agg.'. These inconsistencies in the taxonomic status of the various units within the K. rugosus species complex are discussed, although most of them cannot be distinguished morphologically at present.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 88 , 555–563.     

A benthic predatory fish does not cause selection on armour traits in three‐spined stickleback Gasterosteus aculeatus (Gasterosteiformes: Gasterosteidae)

Predation can promote divergence between prey populations and contribute to ecological speciation. In theory, predators can also constrain prey population divergence. In coastal British Columbia, Canada, Gasterosteus aculeatus (three‐spined stickleback) species pairs only occur in lakes with a single species of predatory fish: Oncorhynchus clarkii (the cutthroat trout). Similar lakes containing additional predatory fish species (Cottus asper, prickly sculpins; Oncorhynchus mykiss, rainbow trout) contain only single species of morphologically intermediate stickleback, suggesting that these predators prevent the coexistence of stickleback species pairs. We conducted a mesocosm experiment to investigate how prickly sculpins might constrain divergence, by quantifying their impact on survival and natural selection on antipredator (armour) traits in F₂ stickleback from a cross between ecologically divergent populations. We tested three hypotheses: (1) sculpin predation on sticklebacks reduces survival in a way that could result in their exclusion from certain niches; (2) sculpins compete with stickleback; (3) sculpins respond to prey vulnerabilities in similar ways to cutthroat trout, tending to constrain rather than to enhance divergence. We found that sculpins significantly reduce stickleback survival, that their presence per se does not reduce growth in stickleback, and that predation did not result in selection on any of the armour traits measured, or on gill raker length, which is an important trophic trait. These results tend to refute hypotheses (2) and (3), while supporting hypothesis (1). © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 877–885.     

Changes in the Growth Capacity of the Developing Wheat Embryo: 1. THE INFLUENCES OF THE ENVELOPING TISSUES11

Grains stimulated to germinate by removal of the outer pericarpshow three types of embryo growth according to their physiologicalage. The first type gives rise only to callus tissue, the secondpredominantly to growth of the coleoptile, which fails to penetratethe testa, and the third, to normal germinative growth. Thesecond type of growth (coleoptile only) corresponds to a conditionreferred to as ‘non-visible’ sprouting, occasionallyfound in prematurely sprouted grains in the field. The phasesof germination capacity are related to total grain moistureand not to the chronological age of the grain, i.e. days post-anthesis.The effects of drying upon grain germinability are also discussedand it is shown that drying can cause both qualitative and quantitativechanges in germination capacity. Key words: Wheat embryo, Germination capacity, Germinability     

The role of ecotoxicity testing in assessing water quality

Abstract Ecotoxicology provides a basis for making decisions on the likely impact of a chemical or effluent on the aquatic environment. It encompasses laboratory ecotoxicity tests of various types to explore relationships between exposure and effect under controlled laboratory conditions, through to studies of the effects of chemicals or effluents under a variety of ecological conditions in complex field ecosystems. This paper will focus on the value of laboratory ecotoxicity tests as a tool in assessing water quality. Laboratory tests are valuable (i) in deriving and assessing water quality criteria, (ii) for screening and ranking chemicals and predicting their hazard and risk, (iii) for establishing dilution levels of chemicals or effluents prior to discharge into water bodies, (iv) in determining cause-effect relationships in post-impact studies, and (v) for establishing and validating field bioindicators. Both the advantages and deficiencies of using ecotoxicological testing for these purposes are illustrated from research with pesticides, metals and sediments. Use of a combination of both laboratory- and field-based ecotoxicology studies is important to gain a full understanding of the effects of chemicals at the ecosystem level.     

METHODS OF ASSESSING THE SPORICIDAL EFFICIENCY OF AN ULTRA-HIGH-TEMPERATURE MILK STERILIZING PLANT I. EXPERIMENTS WITH SUSPENSIONS OF SPORES IN WATER

SUMMARY: A method of assessing the sporicidal efficiency of a UHT milk sterilizing plant operating on water is described. Water heavily contaminated with spores of a strain of Bacillus subtilis was filtered, after treatment in the plant, through membrane filters and the surviving spores estimated by incubation of the membranes in nutrient agar. With this plant a temperature of c . 135° caused a 99·99999% kill of B. subtilis spores. Confirmation of the lethal effects of temperatures above 135° was obtained by passing treated water into 10 gal churns containing sterile concentrated nutrient broth and incubating the churns.     

The Influence of Leaf Position and Defoliation on the Assimilation and Translocation of Carbon in White Clover (Trifolium repens L.) 1. Carbon Distribution Patterns

The assimilation of carbon (C) by, and distribution of ¹⁴C from,leaves at each end of an unbroken sequence of ten mature leaveson the main stolon of clonal plants of white clover (Trifoliumrepens L.) were measured to identify intra-plant factors determiningthe direction of C movement from leaves. Leaves at two intermediatepositions were also measured. Localized movement of ¹⁴C to sinks at the same node as, or atthe one to two nodes immediately behind, the fed leaf accountedfor 40–50% of the total ¹⁴C exported by all measured leaves.A further 50–60% of exported ¹⁴C was therefore availablefor more-distant sinks, and the direction of translocation ofthis C was determined by the relative total strength or demand(number x size x rate of activity or growth) of sinks forwardof, or behind, the leaf in question. Thus 85% of the ¹⁴C exportedfrom the youngest measured leaf moved toward the base of thestolon, while about 60% of the ¹⁴C exported from the oldestleaf moved acropetally. Defoliating plants to leave just one mature leaf on the mainstolon (at any one of the same four positions studied in undefoliatedplants), and no leaves on branches, resulted in: (1) increasednet photosynthetic rate in all residual leaves: (2) increased%export of fixed C from one of the four leaves; (3) increasedexport to the main stolon apex from all except the eldest leaf;(4) increased export to branches from three of the four leaves;and (5) decreased export to stolon tissue and roots from allleaves, within 3 d of defoliation. These responses would seemto ensure the fastest possible replacement of lost leaf areaand, thus, restoration of homeostatic growth. The observed patternsof C assimilation and distribution in both undefoliated anddefoliated white clover plants are consistent with the generalrules of source-sink theory; the distance between sources andcompeting sinks, and relative sink strength, emerge as the mostimportant intra-plant factors governing C movement. These resultsemphasize the need to consider plant morphology, and the modularnature of plant growth, when interpreting patterns of resourceallocation in clonal plants, or plant responses to stressessuch as partial defoliation. Trifolium repens L, white clover, photosynthesis, assimilate translocation, defoliation