Project description:Here we investigate DNA methylation variation in Swedish Arabidopsis thaliana accessions, demonstrating that methylation of transposable elements is temperature sensitive and associated with genetic polymorphism in both cis and trans, whereas gene body methylation is highly correlated with climate of origin and associated with genetic polymorphism in trans that shows evidence of local adaptation. While genome-wide surveys of naturally occurring DNA methylation have been published previously, the degree of genetic control revealed here is unprecedented. Furthermore, the observation that DNA methylation is associated with climate, and is apparently adaptively important, is completely novel. Bisulfite sequencing of 152 Swedish Arabidobsis accessions grown at 10 C and 121 grown at 16 C
Project description:Matching habitat choice is a unique, flexible form of habitat choice based on self-assessment of local performance. This mechanism is thought to play an important role in adaptation and population persistence in variable environments. Nevertheless, the operation of matching habitat choice in natural populations remains to be unequivocally demonstrated. We investigated the association between body colour and substrate use by ground-perching grasshoppers (Sphingonotus azurescens) in an urban mosaic of dark and pale pavements, and then performed a colour manipulation experiment to test for matching habitat choice based on camouflage through background matching. Naturally, dark and pale grasshoppers occurred mostly on pavements that provided matching backgrounds. Colour-manipulated individuals recapitulated this pattern, such that black-painted and white-painted grasshoppers recaptured after the treatment aggregated together on the dark asphalt and pale pavement, respectively. Our study demonstrates that grasshoppers adjust their movement patterns to choose the substrate that confers an apparent improvement in camouflage given their individual-specific colour. More generally, our study provides unique experimental evidence of matching habitat choice as a driver of phenotype-environment correlations in natural populations and, furthermore, suggests that performance-based habitat choice might act as a mechanism of adaptation to changing environments, including human-modified (urban) landscapes.
Project description:Phenotypic plasticity and local adaptation via genetic change are two major mechanisms of response to dynamic environmental conditions. These mechanisms are not mutually exclusive, since genetic change can establish similar phenotypes to plasticity. This connection between both mechanisms raises the question of how much of the variation observed between species or populations is plastic and how much of it is genetic. In this study, we used a structured population of fire salamanders (Salamandra salamandra), in which two subpopulations differ in terms of physiology, genetics, mate-, and habitat preferences. Our goal was to identify candidate genes for differential habitat adaptation in this system, and to explore the degree of plasticity compared to local adaptation. We therefore performed a reciprocal transfer experiment of stream- and pond-originated salamander larvae and analyzed changes in morphology and transcriptomic profile (using species-specific microarrays). We observed that stream- and pond-originated individuals diverge in morphology and gene expression. For instance, pond-originated larvae have larger gills, likely to cope with oxygen-poor ponds. When transferred to streams, pond-originated larvae showed a high degree of plasticity, resembling the morphology and gene expression of stream-originated larvae (reversion); however the same was not found for stream-originated larvae when transferred to ponds, where the expression of genes related to reduction-oxidation processes was increased, possibly to cope with environmental stress. The lack of symmetrical responses between transplanted animals highlights the fact that the adaptations are not fully plastic and that some level of local adaptation has already occurred in this population. This study illuminates the process by which phenotypic plasticity allows local adaptation to new environments and its potential role in the pathway of incipient speciation.
Project description:Here we investigate DNA methylation variation in Swedish Arabidopsis thaliana accessions, demonstrating that methylation of transposable elements is temperature sensitive and associated with genetic polymorphism in both cis and trans, whereas gene body methylation is highly correlated with climate of origin and associated with genetic polymorphism in trans that shows evidence of local adaptation. While genome-wide surveys of naturally occurring DNA methylation have been published previously, the degree of genetic control revealed here is unprecedented. Furthermore, the observation that DNA methylation is associated with climate, and is apparently adaptively important, is completely novel.
Project description:Genome wide DNA methylation profiling of captive chimpanzees of ages spanning the chimpanzee lifespan (whole blood) Methylation levels have been shown to change with age at sites across the human genome. Change at some of these sites is so consistent across individuals that it can be used as an “epigenetic clock” to predict an individual’s chronological age within a few years. Studies of age-related epigenetic change in other mammals, including mice, whales, and canids, show that some but not all of the same loci as in humans undergo age-associated methylation changes. An in-depth comparison of chimpanzees with humans is of interest because the two species are genetically similar but differ in lifespan. To this end, we profiled genome-wide blood methylation levels for 113 samples from 83 chimpanzees aged 1-58 years (26 chimpanzees were sampled at multiple ages during their lifespan). We used this data to build a chimpanzee-specific epigenetic clock model as well as to compare genome-wide patterns of change with age between humans and chimpanzees more generally.
Project description:Despite the close evolutionary relationship and striking genetic similarity between humans and chimpanzees, there are remarkable differences in anatomy, behavior, and disease susceptibility in the two species. One step towards understanding the biological basis of these phenotypic differences is to characterize quantitative differences in levels of expression of genes in humans and chimpanzees. To contribute to such analysis, we compared gene expression patterns in lymphoblastoid cell lines between nine unrelated humans and ten unrelated chimpanzees by using human cDNA microarrays. Hybridizations to arrays containing 43,233 features produced high quality data for 22,879 cDNA clones, representing 20,266 Unigenes. We observed statistically significant differences in transcript levels for 32% of these genes (P < 0.05, Student t test), with about 200 cDNAs showing differences of more than 2-fold (lower bounds of 95% confidence interval). Among these are genes involved in cell surface glycosylation and responses to toxins and viruses. Examination of functional annotations for the differentially expressed genes revealed lower expression of cell cycle and energy pathways genes, and higher expression of chemokines, 26S proteasome and cell motility genes in chimpanzee samples. These genes and pathways could underlie some of the phenotypic differences between humans and chimpanzees. Keywords: other