Spontaneous mutation variation (quantitative manifestation) of some traits of the garden rose

Quantitative variability of four traits (anthocyan coloration, flower aroma, double-flowering capacity, and a flower size) in spontaneous gemmacous mutants (sports) of garden rose may be not accidental but preferably orientated to the increase or decrease in the trait manifestation in the case of transaggressive inheritance by initial hybrid forms of the increased or decreased level of these traits in parents. Revealing this regularity enabled us to evolve a hypothesis explaining the decrease or increase in trait quantitative manifestation in sports by inactivation or elimination resulting from mutations in dominant alleles of the polymer genes responsible either for increasing or decreasing in phenotypic expression. Thus, if the parents of an initial form are known, it is possible to forecast in what way the quantitative characters in somatic mutants of the initial form will change, accidentally or getting preferably higher or lower.     

Rapid generation of plant traits via regulation of DNA mismatch repair

The reversible inhibition of DNA repair is a novel approach to maximize genetic diversity within a plant's genome in order to generate offspring exhibiting important de novo output traits. This process is based on the inhibition of the evolutionarily conserved mismatch repair (MMR) system. In this process, a human dominant negative MMR gene allele is introduced into the germline of a target plant, yielding progeny that can be screened to identify variants with commercially important agronomic output traits. Using this novel strategy, we generated MMR-deficient Arabidopsis thaliana plants that showed genome-wide instability of nucleotide repeats associated with chromosomal microsatellites, in addition to base substitution mutations. Functional screenings of the MMR-deficient Arabidopsis offspring identified variants expressing selectable traits (ethylene insensitivity and salt tolerance), as well as plants exhibiting altered morphologic traits (albinos and dwarfs). We determined by segregation analyses of variant plants that the de novo phenotypes were due to both recessive and dominant genetic mutations. Mutations caused by MMR deficiency showed a different spectrum compared with those derived using ethylmethane sulphonate (EMS) mutagenesis. Our finding demonstrates the feasibility of using reversible MMR deficiency via transient expression of a single human gene product to enhance genetic diversity in plants.     

Treat ’em Mean,Keep ’em (sometimes) Keen: Evolution of Female Preferences for Dominant and Coercive Males

How should females choose their mates if choice is not completely free, but at least partly dictated by outcomes of male–male competition, or sexual coercion? This question is of central importance when evaluating the relationship between sexually antagonistic ‘chase-away’ scenarios and models of more traditional female choice. Currently, there is a mismatch between theories: indirect benefits are seen to play a role in conventional mate choice, whereas they are not predicted to have an influence on the outcome if matings impose direct costs on females. This is at odds with the idea that resistance and preference are two sides of the same coin: either leads to a subset of males enjoying enhanced mating success. In the same way as choosy females benefit from mating with sexy males if this yields sexy sons, females could benefit from being manipulated or ‘seduced’, if the manipulative or seductive ability of males is heritable. Here I build a model where male dominance (or coerciveness) improves his mating success, and this relationship can be modified by female behaviour. This clarifies the definitions of resistance and preference: resisting females diminish the benefit a male gains from being dominant, while preferences enhance this pre-existing benefit enjoyed by dominant males. In keeping with earlier theory, females may evolve to resist costly mating attempts as a counterstrategy to male traits, particularly if male dominance is environmentally rather than genetically determined. Contrary to earlier results, however, indirect benefits are also predicted to influence female mating behaviour, and if sufficiently strong, they may produce female preferences for males that harm them.     

Impact of the use of cryobank samples in a selected cattle breed: a simulation study

Background

High selection pressure on domestic cattle has led to an undesirable increase in inbreeding, as well as to the deterioration of some functional traits which are indirectly selected. Semen stored in a cryobank may be a useful way to redirect selection or limit the loss of genetic diversity in a selected breed. The purpose of this study was to analyse the efficiency of current cryobank sampling methods, by investigating the benefits of using cryopreserved semen in a selection scheme several generations after the semen was collected.

Methods

The theoretical impact of using cryopreserved semen in a selection scheme of a dairy cattle breed was investigated by simulating various scenarios involving two negatively correlated traits and a change in genetic variability of the breed.

Results

Our results indicate that using cryopreserved semen to redirect selection will have an impact on negatively selected traits only if it is combined with major changes in selection objectives or practices. If the purpose is to increase genetic diversity in the breed, it can be a viable option.

Conclusions

Using cryopreserved semen to redirect selection or to improve genetic diversity should be carried out with caution, by considering the pros and cons of prospective changes in genetic diversity and the value of the selected traits. However, the use of genomic information should lead to more interesting perspectives to choose which animals to store in a cryobank and to increase the value of cryobank collections for selected breeds.     

Plant functional composition and ecosystem properties: the case of peatlands in South Africa

The assumption that ecosystems with similar emergent properties consist of similar functional groupings of plant species is tested by comparing three peatlands from different bioregions across South Africa. They are Mfabeni Swamp in the subtropical coastal region, Wakkerstroom on the inland plateau, and Goukou wetland in the Winter Rainfall region of the Western Cape. In each of the three peatlands, about 400 small vegetation plots have been made from which the abundance of each species per wetland can be assessed. The most dominant species in these plots have been investigated for 17 traits. The functional composition of the vegetation types has been compared across the three peatlands and Functional Diversity has been calculated, taking the dominance of each species into account. One peatland differed greatly from the other two, since the dominant species was of a functional type (“Palmiet/woody sedge”) that was very divergent from any other peatland species found in the study. This functional type can be considered an ecosystem engineer and the effects that this functional type has on the ecosystem results in the occurrence of many other functional types that do not occur in the other peatlands. When we consider emergent traits of an ecosystem as a function of all the plant functional traits that occur in that ecosystem, then peatlands can be regarded as a heterogeneous group of ecosystems. Even if emergent properties such as peat formation are similar between ecosystems, those ecosystems may still consist of very different functional groups. Ecosystem engineers have an impact on the final functional composition of an ecosystem and the degree in which ecosystem engineering plays a role in peatlands differs between different peatlands.     

Context-dependent effects of tail-ornament damage on mating success in black grouse

Male black grouse (Tetrao tetrix) may receive damage to theirtail ornaments, the lyre, during goshawk predation attemptsand during fights with other males. In this study we confirma previous observation that black grouse males with damagedtail ornaments suffer reduced mating success. In males thatheld territories on the edge of the leks, tail damage was unrelatedto mating success, whereas in central males damage was negativelycorrelated with mating success. We tested experimentally whetherabsence of damage is used by females in mate choice. In maleswith edge territories, intact, control males had higher matingsuccess than males with cut tails, but in males with centralterritories, lyre cutting had no effect on mating success. Theseresults suggest two interpretations. First, female choice alsodepends on factors other than tail damage such as position onthe lek and dominance. Second, the effect of tail damage iscontext dependent; in males that otherwise meet females standards(e.g., dominant males), the effect of tail damage is negligible,but in less dominant males, tail damage could be used by femalesin mate selection. The second interpretation provides an explanationfor why the data on unmanipulated and manipulated birds differ.In experimental central birds, factors other than tail damageprobably determine male mating success, whereas in experimentaledge birds such factors are probably absent and therefore taildamage is relatively more important. In central unmanipulatedbirds, however, males with natural damage are probably not chosenbecause tail damage and absence of other attractive traits arecorrelated. The absence of an effect on peripheral unmanipulatedbirds may be explained by their overall low mating success     

Species traits for future biomonitoring across ecoregions: patterns along a human-impacted river

1. Current budgets for environmental management are high, tend to increase, and are used to support policy and legislation which is standardized for large geographic units. Therefore, the search for tools to monitor the effects of this investment is a major issue in applied ecology. Ideally, such a biomonitoring tool should: (1) be as general as possible with respect to its geographic application; (2) be as specific as possible by separating different types of human impact on a given ecosystem; (3) reliably indicate changes in human impact of a particular type; and (4) be derived from a sound theoretical concept in ecology. 2. We developed an approach to biomonitoring which matches these ‘ideal’ characteristics by focusing on numerous, general biological species traits (e.g. size, number of descendants per reproductive cycle, parental care, mobility) and on the habitat templet concept, which relates trends in these general species traits to disturbance patterns. Using the French Rhône River and benthic macroinvertebrates as an example, we have used the data to demonstrate a general framework and the potential of our approach rather than to produce a ready-made tool. Our data covered a large river and its major tributaries, which has a catchment that crosses ecoregions, and known gradients and discontinuities in human impact. 3. We applied multivariate analyses to evaluate how the distribution of species traits in invertebrate communities could discriminate environmental differences along the Rhône in comparison to traditionally used approaches (e.g. community structure, based on species abundances, or ecological species traits, such as velocity preferences and pollution tolerance). Invertebrate community structure expressed in terms either of the abundance or the traits of species reliably indicated differences in overall human impact. The community structure based on biological traits was less confounded by natural spatial gradients and reliably indicated human impact, while community structure based on ecological traits was the most confounded by natural spatial gradients and was the poorest indicator of human impact. Community structure based on species abundances was an intermediate indicator of human impact. 4. These results indicate that a revision of biomonitoring approaches which have been based on a single aspect of the biological responses may be warranted. The biological traits of species could separate the different types of human impact. Therefore, the use of these traits in biomonitoring could improve existing multi-metric approaches. Future research has to show if the general applicability of species traits allows the development of a unique biomonitoring tool for running waters of the European Union, for running waters in temperate climates on several continents, for freshwater, marine and terrestrial systems, and/or for global biodiversity assessment.     

Scarlet gilia resistance to insect herbivory: the effects of early season browsing,plant apparency,and phytochemistry on patterns of seed fly attack

Pollen-limited plants are confronted with a difficult tradeoff because they must present showy floral displays to attract pollinators and yet must also minimize their apparency to herbivores. In these systems, traits that increase pollinator visitation may also increase herbivore oviposition and overall plant resistance may therefore be constrained to evolve largely as a correlated response to selection on plant apparency or vigor. We used a family-structured quantitative genetic experiment to evaluate the importance of ungulate browsing, flowering date and plant height (traits that are related to overall vigor), and variation in a putative phytochemical defense (cucurbitacin production) on patterns of seed fly attack in a scarlet gilia population. We found significant genetic variation in the amount of insect damage plants experience in the field, providing evidence that resistance may evolve. In addition, we found that browsing reduced seed fly attack and that oviposition is strongly related to plant size and flowering date; large, early flowering plants experience high attack. In addition, we found that high cucurbitacin production was correlated with low seed fly damage, although this effect was relatively weak.We found directional selection on final plant height and flowering date; tall, early flowering plants had the highest reproductive success. In addition, we found negative directional selection on cucurbitacin production, which may indicate a high cost of cucurbitacin or other functions of this phytochemical. Although seed fly herbivory arguably decreases plant fitness, we found an unexpected positive relationship between damage and fitness. A negative relationship between fitness and damage may be masked in this system through strong positive indirect correlations between patterns of damage and levels of pollinator visitation. Finally, we found significant genetic variation in flowering date, plant height, and cucurbitacin production. Resistance to seed flies may evolve in this population, but largely as a non-adaptive correlated response to selection on overall plant vigor. Phytochemicals may play a more important role in defense in years with high seed fly attack, or when pollen-limitation is less severe.Co-ordinating editor: J. Tuomi     

Evolution of plant resistance and tolerance to frost damage

Plant defence against any type of stress may involve resistance (traits that reduce damage) or tolerance (traits that reduce the negative fitness impacts of damage). These two strategies have been proposed as redundant evolutionary alternatives. A late‐season frost enabled us to estimate natural selection and genetic constraints on the evolution of frost resistance and tolerance in a wild plant species. We employed a genetic selection analysis (which is unbiased by environmental correlations between traits and fitness) on 75 paternal half‐sibling families of annual wild radish [Raphanus raphanistrum (Brassicaceae)]. In an experimental population in southern Ontario, we found strong selection favouring plant resistance to frost, but selection against tolerance to frost. The selection against tolerance may have been caused by a cost of tolerance, as we provide evidence for a negative genetic correlation between tolerance and fitness in the absence of frost damage. Although we found no evidence for the theoretically predicted trade‐off between frost tolerance and resistance among our families, we did detect negative correlational selection acting on the two traits, indicating that natural selection favoured high resistance combined with low tolerance and low resistance coupled with high tolerance, but not high or low levels of both traits together. There were few genetic correlations between the measured traits overall, but frost tolerance was negatively correlated with initial seed mass, and frost resistance was positively correlated with resistance to insect herbivory. Periodic episodes of strong selection such as that caused by the late‐season frost may be disproportionately important in evolution, and are likely becoming more common because of human alterations of the environment.     

Male dominance determines female egg laying rate in crickets

A key prediction of theories of differential allocation and sexual conflict is that male phenotype will affect resource allocation by females. Females may adaptively increase investment in offspring when mated to high quality males to enhance the quality of their offspring, or males may vary in their ability to manipulate female investment post-mating. Males are known to be able to influence female reproductive investment, but the male traits underlying this ability have been little studied in taxa other than birds. We investigated the relationship between male dominance and female oviposition rate in two separate experiments using the field cricket, Gryllus bimaculatus. In both experiments, females mated to more dominant (but not larger) males laid more eggs. This reveals that either females allocate more effort to reproduction after mating with a dominant male or that dominance status is associated with male ability to manipulate their mates. This is the first evidence that dominance, rather than male attractiveness, has a post-copulatory effect on reproductive investment by females.     

Sexes show differential tolerance to spittlebug damage and consequences of damage for multi-species interactions

Antagonists can play a role in sexual system evolution if tolerance or resistance is sex-dependent. Our understanding of this role will be enhanced by consideration of the effects of antagonists on other plant-animal interactions. This study determined whether the sex morphs of a gynodioecious Fragaria virginiana differ in their susceptibility and response to damage by spittlebugs and whether damage altered pollinator attraction traits or interactions with other antagonists. Tolerance, but not resistance, to spittlebugs differed between the sexes. Generally, spittlebugs were more damaging to hermaphrodites than females, a finding in accord with the hypothesis that the pollen-bearing morph is less tolerant of source-damage than the pollen-sterile morph when damage is incurred during flowering. In both sex morphs, spittlebugs reduced inflorescence height, increased petal size, but did not affect the number of open flowers per day, suggesting that the net effect of damage may be to increase pollinator attraction. Spittlebug infestation modified interactions with other antagonists in a sex-dependent manner: spittlebugs reduced attack by bud-clipping weevils in hermaphrodites but increased infection by leaf fungi in females. The complex interactions between plant sex, antagonists, and pollinator attraction documented here emphasize the importance of considering sex-differential multi-species interactions in plant sexual evolution.     

A functional assessment of the response of grassland vegetation to reduced grazing and abandonment

Question: Predicting the impact of land‐use change on vegetation is vital to understanding how biodiversity and ecosystem function may respond. Is it correct to assume that abandonment is an extreme form of grazing reduction? Location: Borders and central Scotland. Methods: The analysis used data sets from two identical experiments where the impacts of two unfertilized, extensively grazed treatments and one unfertilized abandoned treatment were compared against the species dynamics of a pasture subject to normal, productive grazing management over a 16‐year period. Initial multivariate analysis using Principal Response Curves was used to assess if particular traits were associated with either extensive or abandoned treatments, and was checked using univariate tests of individual traits. RLQ analysis followed by clustering into response groups was used to assess if species behaved in a similar manner between sites. Results: For many traits/attributes the shift in value or proportion was approximately linear across the extensification treatments as grazing was removed. However, certain traits showed step changes and quadratic responses. Leaf dry matter content, an important effect trait, was in the latter group. Most traits/attributes and species behaved similarly at the two sites. However, traits such as regenerative strategy, seed length, longevity and mass and seed bank type behaved differently, indicating that they are not predictable response traits. Conclusion: The results indicate that responses to grazing removal during extensification are largely straightforward and largely independent of species pool. However, there are discrepancies that suggest that simple analyses of the impacts of land‐use changes such as grazing reduction may hide more complex responses.     

Heterozygote Advantage and the Evolution of a Dominant Diploid Phase

The life cycle of eukaryotic, sexual species is divided into haploid and diploid phases. In multicellular animals and seed plants, the diploid phase is dominant, and the haploid phase is reduced to one, or a very few cells, which are dependent on the diploid form. In other eukaryotic species, however, the haploid phase may dominate or the phases may be equally developed. Even though an alternation between haploid and diploid forms is fundamental to sexual reproduction in eukaryotes, relatively little is known about the evolutionary forces that influence the dominance of haploidy or diploidy. An obvious genetic factor that might result in selection for a dominant diploid phase is heterozygote advantage, since only the diploid phase can be heterozygous. In this paper, I analyze a model designed to determine whether heterozygote advantage could lead to the evolution of a dominant diploid phase. The main result is that heterozygote advantage can lead to an increase in the dominance of the diploid phase, but only if the diploid phase is already sufficiently dominant. Because the diploid phase is unlikely to be increased in organisms that are primarily haploid, I conclude that heterozygote advantage is not a sufficient explanation of the dominance of the diploid phase in higher plants and animals.     

Mutational Load and the Transition between Diploidy and Haploidy in Experimental Populations of the Yeast Saccharomyces cerevisiae

Mutations were accumulated over hundreds of generations in a mutator strain of yeast in a constant laboratory environment. This ensured that mutations were frequent and that the quality of environment remained unchanged. Mutations were accumulated in asexual populations of diploids but their impact on fitness was tested both for the diploid clones and for haploid clones derived from them. Dozens of harmful and lethal mutations accumulated in diploids, but important phenotypic traits, such as maximum growth rate, did not deteriorate by more than 10%. There were no signs of decline in population size. In strong contrast, the populations of haploids derived from the diploids suffered from high mortality; their density was reduced by more than three orders of magnitude. These findings indicate how ineffective natural selection can be in removing deleterious mutations from populations of clonally reproducing diploids. They also suggest that phenotypic assays of heterozygous diploids may be of little value as indicators of increasing genetic degeneration.     

Evidence that mutation accumulation does not cause aging in Saccharomyces cerevisiae

The concept that mutations cause aging phenotypes could not be directly tested previously due to inability to identify age‐related mutations in somatic cells and determine their impact on organismal aging. Here, we subjected Saccharomyces cerevisiae to multiple rounds of replicative aging and assessed de novo mutations in daughters of mothers of different age. Mutations did increase with age, but their low numbers, < 1 per lifespan, excluded their causal role in aging. Structural genome changes also had no role. A mutant lacking thiol peroxidases had the mutation rate well above that of wild‐type cells, but this did not correspond to the aging pattern, as old wild‐type cells with few or no mutations were dying, whereas young mutant cells with many more mutations continued dividing. In addition, wild‐type cells lost mitochondrial DNA during aging, whereas shorter‐lived mutant cells preserved it, excluding a causal role of mitochondrial mutations in aging. Thus, DNA mutations do not cause aging in yeast. These findings may apply to other damage types, suggesting a causal role of cumulative damage, as opposed to individual damage types, in organismal aging.     

Induced responses in three tropical dry forest plant species – direct and indirect effects on herbivory

Induced changes in plant quality are hypothesized to reduce herbivore numbers and subsequent damage to the plant. The resultant decrease in herbivory may be due to direct negative impacts on herbivores, through the reduction in foliage quality as food, or due to indirect effects of plant-induced traits interacting with the third trophic level, increasing predation and parasitism rates on herbivores. The relative importance of induced responses as direct and/or indirect defenses has not been evaluated in natural systems. Moreover, few studies have evaluated the influence of early-season damage on late-season herbivory in natural systems, particularly in the tropics. The presence of induced responses and subsequent impact on folivory as a consequence of early-season damage were evaluated in three plant species ( Croton pseudoniveus , Bursera instabilis and Piper stipulaceum ) in a tropical dry forest in Mexico. A two-factorial experiment was applied to determine if induced responses influenced subsequent herbivory directly, by reducing foliage quality, or indirectly, through their interaction with parasitoids and predatory arthropods. Plants from all three species with reduced early-season damage had higher herbivory rates through the rest of the growing season, compared to plants that were damaged during leaf expansion. Chemical analyses showed that early-season damage induced the production of total phenolics and condensed tannins for C. pseudoniveus and B. instabilis , respectively. The mechanism by which these compounds affected subsequent herbivory was most likely by directly reducing foliage quality as food for herbivores, given that predatory arthropods and parasitoids had no effects on herbivory in this study. I conclude that early-season damage in these three species influenced later-season herbivory through the induction of plant responses that may act to reduce plant quality as food for herbivores.     

Dominant Maternal-Effect Mutations Causing Embryonic Lethality in Caenorhabditis Elegans

We undertook screens for dominant, temperature-sensitive, maternal-effect embryonic-lethal mutations of Caenorhabditis elegans as a way to identify certain classes of genes with early embryonic functions, in particular those that are members of multigene families and those that are required in two copies for normal development. The screens have identified eight mutations, representing six loci. Mutations at three of the loci result in only maternal effects on embryonic viability. Mutations at the remaining three loci cause additional nonmaternal (zygotic) effects, including recessive lethality or sterility and dominant male mating defects. Mutations at five of the loci cause visible pregastrulation defects. Three mutations appear to be allelic with a recessive mutation of let-354. Gene dosage experiments indicate that one mutation may be a loss-of-function allele at a haploin sufficient locus. The other mutations appear to result in gain-of-function "poison" gene products. Most of these become less deleterious as the relative dosage of the corresponding wild-type allele is increased; we show that relative self-progeny viabilities for the relevant hermaphrodite genotypes are generally M/+/+ greater than M/+ greater than M/M/+ greater than M/Df greater than M/M, where M represents the dominant mutant allele.     

Seedling resistance to herbivory as a predictor of relative abundance in a synthesised prairie community

In a laboratory experiment seedlings of 24 perennial herbaceous prairie species were offered to the omnivorous cricket Acheta domestica in an extended feeding trial. Leaf damage was monitored daily allowing an index of palatability to be calculated for each plant species. The index of palatability successfully predicted relative abundance within the same set of species in an independently-conducted study involving community assembly from seed in low-fertility plots. These results support the hypothesis that resistance to herbivory may be an important component of plant fitness in unproductive vegetation. However, the correlation between palatability and community composition may be interpreted as a positive association between traits that lead to high competitive ability and herbivory resistance. There is a need to establish whether the success of the dominant grasses at Cedar Creek arises from their superior ability to capture nitrogen from low external concentrations or is, rather, due to their superior ability to minimise nitrogen loss to herbivores.     

Strong ecological but weak evolutionary effects of elevated CO2 on a recombinant inbred population of Arabidopsis thaliana

Increases in atmospheric CO2 concentration have an impact on plant communities by influencing plant growth and morphology, species interactions, and ecosystem processes. These ecological effects may be accompanied by evolutionary change if elevated CO2 (eCO2) alters patterns of natural selection or expression of genetic variation. Here, a statistically powerful quantitative genetic experiment and manipulations of CO2 concentrations in a field setting were used to investigate how eCO2 impacts patterns of selection on ecologically important traits in Arabidopsis thaliana; heritabilities, which influence the rate of response to selection; and genetic covariances between traits, which may constrain responses to selection. CO2 had strong phenotypic effects; plants grown in eCO2 were taller and produced more biomass and fruits. Also, significant directional selection was observed on many traits and significant genetic variation was observed for all traits. However, no evolutionary effect of eCO2 was detected; patterns of selection, heritabilities and genetic correlations corresponded closely in ambient and elevated CO2 environments. The data suggest that patterns of natural selection and the quantitative genetic parameters of this A. thaliana population are robust to increases in CO2 concentration and that responses to eCO2 will be primarily ecological.