Transgenerational effects in asexually reproduced offspring of Populus

The response of trees to a changing climate can be affected by transgenerational phenotypic plasticity, i.e. phenotypic variation that is conserved and transferred to the offspring. Transgenerational plasticity that is influenced by epigenetics (heritable changes in gene function that do not result from changes in DNA sequence) during both sexual and asexual reproduction are of major relevance for adaptation of plants to climate change. To understand the transgenerational effects on the responses of vegetatively propagated poplar (Populus deltoides and P. trichocarpa) ramets (cuttings) to a changing environment, we tested whether the temperature and photoperiod experienced by the mother trees (genets) persistently affects the phenology of the cuttings grown in a common environment. We weekly monitored the bud phenology of the cuttings collected from the parent trees that have been growing across Europe along a >2100 km latitudinal gradient for at least 18 years. In addition, we asked whether there was variation in DNA methylation as measured by Methylation Sensitive Amplified Fragment Length Polymorphism (MSAPs) in the clones due to the different environmental conditions experienced by the parent trees. Our results indicate a transgenerational effect on bud phenology in the asexually reproduced offspring (vegetative cuttings). The temperatures experienced by the parent tree clones (from different geographic regions) altered the bud flush of the cuttings in the common garden. However, no significant epigenetic variation was detected in the cuttings of the parent trees within single genotypes growing under different climates. In sum, our results show that trees have the potential to respond to rapid climate change but the mechanism behind these changes needs to be further investigated by more powerful molecular methods like whole-genome bisulphite sequencing techniques

Bio-Inspired Optics: Liquid lenses imitating eye reflexes

Biological vision systems such as animals or insects eye exhibit simplicity and multiplicity of operational characteristics that are not available to the traditional optical technologies. The distinctive features of the visual organs of living species allowing the adaptation for the environment using visual-motor reactions, inspired researchers to develop numerous biomimetic compact optical devices [1-4]. We demonstrate a laser controlled liquid-based tunable optical system replicating the eye behavior including the accommodation, the pupillary light response and the optokinetic response. A liquid droplet serving as a multifunctional lens consist of the mixture of tensioactive liquid and volatile liquid with low surface tension. The actuation principle is based on action of thermocapillary and solutocapillary forces generated by a thermal action of the laser beam. The laser heating lowers the fraction of volatile liquid resulting in an increase in surface tension. The increase in the laser power leads to a shrinkage of the droplet and consequently to the increase of the surface curvature. The decrease in the power results in a spreading of the droplet and hence to the decrease of the curvature. This behavior of the droplet is similar to the eye accommodation reflex and the pupillary light reflex in response to the intensity of light. To validate the proposed concept ethylene glycol/isopropyl alcohol mixture dyed with methyl violet for absorption of the laser radiation (532 nm) were used. The volume of mixture (2 microliter) was placed in a sealed optically transparent microcell. Fig. 1(a) shows variation of the focal length and the aperture (images) of the droplet in response to the laser power variation. Over the range of laser power from 2 to 30 mW the focal length changed from 40 to 15 mm. The droplet curvature changing with the supplied power is shown in Fig. 1(b). The focus adjustment time in response to the laser power changing layes from hundreds ms to a few seconds. Fig 1(c) shows an ability the droplet to move on the substrate toward a new position of the laser beam that replicates the optokinetic response of the eye. Speed of the droplet motion reaches 100 µm/s. Please click Additional Files below to see the full abstract

Epigenetic Response to Habitat Change: Changes Variation in DNA Methylation Frequencies and Generational Transmission Vary with Invasion Status

Epigenetic mechanisms may be important for a native species’ response to rapid environmental change. Red Imported Fire Ants (Solenopsis invicta Santschi, 1916) were recently introduced to areas occupied by the Eastern Fence Lizard (Sceloporus undulatus Bosc & Daudin, 1801). Behavioral, morphological and physiological phenotypes of the Eastern Fence Lizard have changed following invasion, creating a natural biological system to investigate environmentally induced epigenetic changes. We tested for variation in DNA methylation patterns in Eastern Fence Lizard populations associated with different histories of invasion by Red Imported Fire Ants. At methylation sensitive amplified fragment length polymorphism loci, we detected a higher diversity of methylation in Eastern Fence Lizard populations from Fire Ant uninvaded versus invaded sites, and uninvaded sites had higher methylation. Our results suggest that invasive species may alter methylation frequencies and the pattern of methylation among native individuals. While our data indicate a high level of intrinsic variability in DNA methylation, DNA methylation at some genomic loci may underlie observed phenotypic changes in Eastern Fence Lizard populations in response to invasion of Red Imported Fire Ants. This process may be important in facilitating adaptation of native species to novel pressures imposed by a rapidly changing environment

Epigenetic response to environmental change: DNA methylation varies with invasion status

Epigenetic mechanisms may be important for a native species’ response to rapid environmental change. Red Imported Fire Ants (Solenopsis invicta Santschi, 1916) were recently introduced to areas occupied by the Eastern Fence Lizard (Sceloporus undulatus Bosc & Daudin, 1801). Behavioral, morphological and physiological phenotypes of the Eastern Fence Lizard have changed following invasion, creating a natural biological system to investigate environmentally induced epigenetic changes.We tested for variation in DNA methylation patterns in Eastern Fence Lizard populations associated with different histories of invasion by Red Imported Fire Ants. At methylation sensitive amplified fragment length polymorphism loci, we detected a higher diversity of methylation in Eastern Fence Lizard populations from Fire Ant uninvaded versus invaded sites, and uninvaded sites had higher methylation. Our results suggest that invasive species may alter methylation frequencies and the pattern of methylation among native individuals. While our data indicate a high level of intrinsic variability in DNA methylation, DNA methylation at some genomic loci may underlie observed phenotypic changes in Eastern Fence Lizard populations in response to invasion of Red Imported Fire Ants. This process may be important in facilitating adaptation of native species to novel pressures imposed by a rapidly changing environment

Parallel functional differentiation of an invasive annual plant on two continents.

Rapid local adaptation frequently occurs during the spread of invading species. It remains unclear, however, how consistent, and therefore potentially predictable, such patterns of local adaptation are. One approach to this question is to measure patterns of local differentiation in functional traits and plasticity levels in invasive species in multiple regions. Finding consistent patterns of local differentiation in replicate regions suggests that these patterns are adaptive. Further, this outcome indicates that the invading species likely responds predictably to selection along environmental gradients, even though standing genetic variation is likely to have been reduced during introduction. We studied local differentiation in the invasive annual plant Erodium cicutarium in two invaded regions, California and Chile. We collected seeds from across strong gradients in precipitation and temperature in Mediterranean-climate parts of the two regions (10 populations per region). We grew seeds from maternal families from these populations through two generations and exposed the second generation to contrasting levels of water and nutrient availability. We measured growth, flowering time and leaf functional traits across these treatments to obtain trait means and plasticity measures. We found strong differentiation among populations in all traits. Plants from drier environments flowered earlier, were less plastic in flowering time and reached greater size in all treatments. Correlations among traits within regions suggested a coordinated evolutionary response along environmental gradients associated with growing season length. There was little divergence in traits and trait intercorrelations between regions, but strongly parallel divergence in traits within regions. Similar, statistically consistent patterns of local trait differentiation across two regions suggest that local adaptation to environmental gradients has aided the spread of this invasive species, and that the formation of ecotypes in newly invaded environments has been relatively consistent and predictable

Digital evolution in time-dependent fitness landscapes

We study the response of populations of digital organisms that adapt to a time-varying (periodic) fitness landscape of two oscillating peaks. We corroborate in general predictions from quasi-species theory in dynamic landscapes, such as adaptation to the average fitness landscape at small periods (high frequency) and quasistatic adaptation at large periods (low frequency). We also observe adaptive phase shifts (time tags between a change in the fitness landscape and art adaptive change in the population) that indicate a low-pass filter effect, in agreement with existing theory,. Finally, we witness long-term adaptation to fluctuating environments not anticipated in previous theoretical work

Frequency responses of age-structured populations: Pacific salmon as an example

Increasing evidence of the effects of changing climate on physical ocean conditions and long-term changes in fish populations adds to the need to understand the effects of stochastic forcing on marine populations. Cohort resonance is of particular interest because it involves selective sensitivity to specific time scales of environmental variability, including that of mean age of reproduction, and, more importantly, very low frequencies (i.e., trends). We present an age-structured model for two Pacific salmon species with environmental variability in survival rate and in individual growth rate, hence spawning age distribution. We use computed frequency response curves and analysis of the linearized dynamics to obtain two main results. First, the frequency response of the population is affected by the life history stage at which variability affects the population; varying growth rate tends to excite periodic resonance in age structure, while varying survival tends to excite low-frequency fluctuation with more effect on total population size. Second, decreasing adult survival strengthens the cohort resonance effect at all frequencies, a finding that addresses the question of how fishing and climate change will interact.Comment: much revised: the version accepted by Theoretical Population Biolog

Climate-Related Floral and Vegetative Size Variation in Leptosiphon androsaceus (Polemoniaceae)

Phenotypic plasticity in plants is a vital adaptive response to changing environmental conditions. Floral and vegetative morphology often varies as biotic and abiotic factors vary. Variation is the basis of evolution, and natural selection, acting on trait variation, can lead to speciation. For this study, floral and vegetative character traits of false babystars (Leptosiphon androsaceus, Polemoniaceae) were analyzed within four populations at Henry W. Coe State Park in 2011. Traits were measured to assess changes in size along a moisture availability gradient. Stable carbon isotope ratio samples were collected to measure integrated water-use efficiency (WUE) as it related to precipitation and floral size. Sizes of floral and vegetative characters varied significantly between the drier and wetter regions. Floral and vegetative character sizes for L. androsaceus decreased from the wetter to the drier region. The ratio of floral area/leaf area increased as precipitation decreased, suggesting that leaves may have incurred a physiological cost from floral growth within the drier region. A difference in WUE, as it related to trait size and precipitation, was not found for this study year. These results provide evidence that floral and vegetative characters of L. androsaceus vary in size in response to water-limiting conditions