How sensitive is the compensating income variation to severity and adaptation?

Knowing the monetary value individuals place on health is essential in tackling resource allocation between health and other uses. However, health conditions vary greatly, not only with respect to main characteristics but also by severity and duration. We apply the compensating income variation (CIV) method to data from the Swiss Household Panel, years 2004–2019, to explore the sensitivity of CIV estimates to severity and adaptation across five different health conditions: headaches, back problems, sleep problems, fatigue, and chronic illness. Accounting for income endogeneity in the life-satisfaction equations and adjusting for individual random effects, we found the CIV estimates to range from $3184 for moderate headaches (women) to $100,066 for severe fatigue (men). Individuals with severe conditions needed to be compensated about three times more than those suffering less. Across the five conditions with two severity levels explored for adaptation, individuals only adapted to moderate headaches and severe sleep problems. In conclusion, not only does the value of health conditions vary greatly, but within each health condition its value on average triples when severe condition is reported as opposed to moderate. Adaptation plays a minor role in CIV estimates for the five health conditions explored.     

Choline dehydrogenase polymorphism rs12676 is a functional variation and is associated with changes in human sperm cell function

Approximately 15% of couples are affected by infertility and up to half of these cases arise from male factor infertility. Unidentified genetic aberrations such as chromosomal deletions, translocations and single nucleotide polymorphisms (SNPs) may be the underlying cause of many cases of idiopathic male infertility. Deletion of the choline dehydrogenase (Chdh) gene in mice results in decreased male fertility due to diminished sperm motility; sperm from Chdh(-/-) males have decreased ATP concentrations likely stemming from abnormal sperm mitochondrial morphology and function in these cells. Several SNPs have been identified in the human CHDH gene that may result in altered CHDH enzymatic activity. rs12676 (G233T), a non-synonymous SNP located in the CHDH coding region, is associated with increased susceptibility to dietary choline deficiency and risk of breast cancer. We now report evidence that this SNP is also associated with altered sperm motility patterns and dysmorphic mitochondrial structure in sperm. Sperm produced by men who are GT or TT for rs12676 have 40% and 73% lower ATP concentrations, respectively, in their sperm. rs12676 is associated with decreased CHDH protein in sperm and hepatocytes. A second SNP located in the coding region of IL17BR, rs1025689, is linked to altered sperm motility characteristics and changes in choline metabolite concentrations in sperm.     

Mitochondrial adaptation in obesity is a ClpPicated business

Quality control systems that maintain mitochondrial oxidative phosphorylation (OXPHOS) include rescue by mitochondrial fusion, elimination of dysfunctional mitochondria by mitophagy, and degradation of damaged proteins by proteases. ClpP is an ATP‐dependent protease located in the mitochondrial matrix and mutated in Perrault syndrome, causing gonadal atrophy and hearing loss. Given that hearing loss is common in mitochondrial diseases caused by mtDNA mutations, ClpP was proposed to be part of the quality control system to maintain proper mitochondrial OXPHOS function. Two recent studies independently report that deletion of ClpP in mice protects from insulin resistance and obesity by increasing mitochondrial OXPHOS capacity and browning in gonadal white adipose tissue and mitochondrial coupling in brown adipose tissue 1 , 2 . Furthermore, liver‐ and muscle‐specific deletion of ClpP has no major effects on insulin resistance. These studies reveal that ClpP might be involved in tissue‐specific mitochondrial remodeling in response to metabolic demands, rather than exclusively removing damaged proteins to maintain OXPHOS capacity.     

The role of tooth enamel mechanical properties in primate dietary adaptation

Primate teeth adapt to the physical properties of foods in a variety of ways including changes in occlusal morphology, enamel thickness, and overall size. We conducted a comparative study of extant primates to examine whether their teeth also adapt to foods through variation in the mechanical properties of the enamel. Nanoindentation techniques were used to map profiles of elastic modulus and hardness across tooth sections from the enamel-dentin junction to the outer enamel surface in a broad sample of primates including apes, Old World monkeys, New World monkeys, and lemurs. The measured data profiles feature considerable overlap among species, indicating a high degree of commonality in mechanical properties. These results suggest that differences in the load-bearing capacity of primate molar teeth are more a function of morphology-particularly tooth size and enamel thickness-than of underlying mechanical properties.     

Distribution and variation in enamel structure in the oral teeth of sarcopterygians: Its significance for the evolution of a protoprismatic enamel

The property of tooth enamel to resist alteration during fossilization, is used to analyse the unique arrangements of biological crystallites amongst genera of Paleozoic sarcopterygians, with both polarized light and s.e.m. Previous concepts of crystallite organization in reptiles and mammal‐like reptiles are evaluated. Two of the Devonian sarcopterygians, are shown to exhibit a protoprismatic pattern, identical with that of a stem group therian. The patterns of crystallites, together with the arrangement of incremental lines establish that this tissue is solely an ectodermal product; monotypic enamel, in contrast to bitypic enamel with two cell products contributing to it as in enameloid or acrodin. Each genus examined has a different pattern, of significance in considering relationships amongst sarcopterygians. Recent information on ganoine and some new findings on enamel in extant lungfishes have led to the conclusion that types of monotypic enamel are present in both actinopterygians and sarcopterygians, and challenges the use of monotypic enamel as a synapomorphy of sarcopterygians in cladistic analyses.     

Trait dimensionality explains widespread variation in local adaptation

All species are locked in a continual struggle to adapt to local ecological conditions. In cases where species fail to locally adapt, they face reduced population growth rates, or even local extinction. Traditional explanations for limited local adaptation focus on maladaptive gene flow or homogeneous environmental conditions. These classical explanations have, however, failed to explain variation in the magnitude of local adaptation observed across taxa. Here we show that variable levels of local adaptation are better explained by trait dimensionality. First, we develop and analyse mathematical models that predict levels of local adaptation will increase with the number of traits experiencing spatially variable selection. Next, we test this prediction by estimating the relationship between dimensionality and local adaptation using data from 35 published reciprocal transplant studies. This analysis reveals a strong correlation between dimensionality and degree of local adaptation, and thus provides empirical support for the predictions of our model.     

Activity variation in alcohol dehydrogenase paralogs is associated with adaptation to cactus host use in cactophilic Drosophila

Drosophila mojavensis and Drosophila arizonae are species of cactophilic flies that share a recent duplication of the alcohol dehydrogenase (Adh) locus. One paralog (Adh-2) is expressed in adult tissues and the other (Adh-1) in larvae and ovaries. Enzyme activity measurements of the ADH-2 amino acid polymorphism in D. mojavensis suggest that the Fast allozyme allele has a higher activity on 2-propanol than 1-propanol. The Fast allele was found at highest frequency in populations that utilize hosts with high proportions of 2-propanol, while the Slow allele is most frequent in populations that utilize hosts with high proportions of 1-propanol. This suggests that selection for ADH-2 allozyme alleles with higher activity on the most abundant alcohols is occurring in each D. mojavensis population. In the other paralog, ADH-1, significant differences between D. mojavensis and D. arizonae are associated with a previously shown pattern of adaptive protein evolution in D. mojavensis. Examination of protein sequences showed that a large number of amino acid fixations between the paralogs have occurred in catalytic residues. These changes are potentially responsible for the significant difference in substrate specificity between the paralogs. Both functional and sequence variation within and between paralogs suggests that Adh has played an important role in the adaptation of D. mojavensis and D. arizonae to their cactophilic life.     

Individual variation in enamel structure of human mandibular first premolars

Nine human mandibular first premolars were examined to assess variation in external morphology and enamel structural organization within a tooth type. The relationship of enamel ultrastructure to gross dental morphology was also studied. The teeth were cut in the mesiodistal direction just lingual to the buccal cusp, and etched. Montages were constructed of the cut enamel surface photographed in the scanning electron microscope at 100 X magnification. Parameters were measured and correlation coefficients were calculated for the comparison of various odontometric features. The mesiodistal and buccolingual dimensions were highly correlated and the occlusal thickness of enamel was significantly correlated to crown height but not crown width. Hunter-Schreger bands were less pronounced in fossa areas than at lateral aspects, cusps, or ridges; these bands were directly related to the geometry of the tooth. It was concluded that within this tooth type, there is a large amount of individual variation not only in gross morphology but also in enamel ultrastructure. This result underscores the fact that interspecific comparisons must be made with care.     

Genetic variation underlying local adaptation of diapause induction along a cline in a butterfly

Diapause is a life history strategy allowing individuals to arrest development until favourable conditions return, and it is commonly induced by shortened day length that is latitude specific for local populations. Although understanding the evolutionary dynamics of a threshold trait like diapause induction provides insights into the adaptive process and adaptive potential of populations, the genetic mechanism of variation in photoperiodic induction of diapause is not well understood. Here, we investigate genetic variation underlying latitudinal variation in diapause induction and the selection dynamics acting upon it. Using a genomewide scan for divergent regions between two populations of the butterfly Pararge aegeria that differ strongly in their induction thresholds, we identified and investigated the patterns of variation in those regions. We then tested the association of these regions with diapause induction using between‐population crosses, finding significant SNP associations in four genes present in two chromosomal regions, one with the gene period, and the other with the genes kinesin, carnitine O‐acetyltransferase and timeless. Patterns of allele frequencies in these two regions in population samples along a latitudinal cline suggest strong selection against heterozygotes at two genes within these loci (period, timeless). Evidence for additional loci modifying the diapause decision was found in patterns of allelic change in relation to induction thresholds over the cline, as well as in backcross analyses. Taken together, population‐specific adaptations of diapause induction appear to be due to a combination of alleles of larger and smaller effect size, consistent with an exponential distribution of effect sizes involved in local adaption.     

Apparatus architecture of the conodont Nicoraella kockeli (Gondolelloidea,Prioniodinina) constrains functional interpretations

We reconstruct the apparatus architecture of the gondollelid conodont Nicoraella kockeli based on fused clusters from the early Middle Triassic (middle Anisian, Pelsonian) of Luoping County, east Yunnan Province, south‐west China. This material was characterized non‐invasively using synchrotron x‐ray tomographic microscopy and the ensuing data analysed using computed tomography, allowing us to infer the composition, homologies and architectural arrangement of elements within the apparatus. Much of the original three‐dimensional architecture of the apparatus is preserved and our apparatus reconstruction is the best characterized of any taxon within the superfamily Gondolelloidea. This allows us to test architectural models for gondolelloids and prioniodinins, more generally, as well as the functional interpretations based upon them. In particular, we reject a recent functional interpretation of the conodont feeding apparatus which was based on a biomechanically‐optimized inference of apparatus architecture in a close gondolelloid relative of Nicoraella. Nevertheless, our architectural model provides a foundation for future functional interpretations of gondolleloids and prioniodinins, more generally.     

High-throughput biochemical profiling reveals functional adaptation of a bacterial Argonaute

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Effects of founding genetic variation on adaptation to a novel resource

Population genetic theory predicts that adaptation in novel environments is enhanced by genetic variation for fitness. However, theory also predicts that under strong selection, demographic stochasticity can drive populations to extinction before they can adapt. We exposed wheat-adapted populations of the flour beetle (Tribolium castaneum) to a novel suboptimal corn resource, to test the effects of founding genetic variation on population decline and subsequent extinction or adaptation. As previously reported, genetically diverse populations were less likely to go extinct. Here, we show that among surviving populations, genetically diverse groups recovered faster after the initial population decline. Within two years, surviving populations significantly increased their fitness on corn via increased fecundity, increased egg survival, faster larval development, and higher rate of egg cannibalism. However, founding genetic variation only enhanced the increase in fecundity, despite existing genetic variation-and apparent lack of trade-offs-for egg survival and larval development time. Thus, during adaptation to novel habitats the positive impact of genetic variation may be restricted to only a few traits, although change in many life-history traits may be necessary to avoid extinction. Despite severe initial maladaptation and low population size, genetic diversity can thus overcome the predicted high extinction risk in new habitats.     

Behavioural variation in 172 small-scale societies indicates that social learning is the main mode of human adaptation

The behavioural variation among human societies is vast and unmatched in the animal world. It is unclear whether this variation is due to variation in the ecological environment or to differences in cultural traditions. Underlying this debate is a more fundamental question: is the richness of humans’ behavioural repertoire due to non-cultural mechanisms, such as causal reasoning, inventiveness, reaction norms, trial-and-error learning and evoked culture, or is it due to the population-level dynamics of cultural transmission? Here, we measure the relative contribution of environment and cultural history in explaining the behavioural variation of 172 Native American tribes at the time of European contact. We find that the effect of cultural history is typically larger than that of environment. Behaviours also persist over millennia within cultural lineages. This indicates that human behaviour is not predominantly determined by single-generation adaptive responses, contra theories that emphasize non-cultural mechanisms as determinants of human behaviour. Rather, the main mode of human adaptation is social learning mechanisms that operate over multiple generations.     

Natural variation, functional divergence, and local adaptation of nucleotide binding site sequences in Rhododendron (Ericaceae)

To further understand natural variation and local adaptation in the evolution of plant defense, we analyzed polymorphism data of nucleotide-binding site (NBS) sequences of Rhododendron at both the species and population levels. Multiple duplication events were found in NBS sequence evolution in Rhododendron genomes, which resulted in six clades: A–F. Our results of several NBS clade pair comparisons showed significant evolutionary rate changes based on differences in substitution rates between NBS-encoding protein clades (type I functional divergence). Pairwise comparisons of NBS clades further revealed that many amino acids displayed radical biochemical property changes causing a shift in amino acid preferences between NBS-encoding protein clades (type II functional divergence). Such divergent evolution of NBSs is likely a consequence of positive selection related to differentiation of recognition signals in response to different pathogens. Primers specific to clades B and C, which differed in the number of radical amino acid changes causing type II functional divergence and levels of nucleotide diversities, were further used to amplify population clades B and C NBS sequences of Rhododendron formosanum populations. Higher levels of net nucleotide divergences (measured by D _a) between R. formosanum populations were found based on NBS sequences of population clade B compared to population clade C, suggesting local adaptation of population clade B NBS sequences. Local adaptation can be further inferred for R. formosanum population clade B NBS sequences because of significant Φ _ST based on variation in nonsynonymous substitutions. Furthermore, local adaptation was also suggested by no significant correlation of population pairwise F _ST between population clades B and C in R. formosanum.     

Mechanisms driving plant functional trait variation in a tropical forest

Plant functional trait variation in tropical forests results from taxonomic differences in phylogeny and associated genetic differences, as well as, phenotypic plastic responses to the environment. Accounting for the underlying mechanisms driving plant functional trait variation is important for understanding the potential rate of change of ecosystems since trait acclimation via phenotypic plasticity is very fast compared to shifts in community composition and genetic adaptation. We here applied a statistical technique to decompose the relative roles of phenotypic plasticity, genetic adaptation, and phylogenetic constraints. We examined typically obtained plant functional traits, such as wood density, plant height, specific leaf area, leaf area, leaf thickness, leaf dry mass content, leaf nitrogen content, and leaf phosphorus content. We assumed that genetic differences in plant functional traits between species and genotypes increase with environmental heterogeneity and geographic distance, whereas trait variation due to plastic acclimation to the local environment is independent of spatial distance between sampling sites. Results suggest that most of the observed trait variation could not be explained by the measured environmental variables, thus indicating a limited potential to predict individual plant traits from commonly assessed parameters. However, we found a difference in the response of plant functional traits, such that leaf traits varied in response to canopy‐light regime and nutrient availability, whereas wood traits were related to topoedaphic factors and water availability. Our analysis furthermore revealed differences in the functional response of coexisting neotropical tree species, which suggests that endemic species with conservative ecological strategies might be especially prone to competitive exclusion under projected climate change.     

Widespread parallel population adaptation to climate variation across a radiation: implications for adaptation to climate change

Global warming will impact species in a number of ways, and it is important to know the extent to which natural populations can adapt to anthropogenic climate change by natural selection. Parallel microevolution within separate species can demonstrate natural selection, but several studies of homoplasy have not yet revealed examples of widespread parallel evolution in a generic radiation. Taking into account primary phylogeographic divisions, we investigate numerous quantitative traits (size, shape, scalation, colour pattern and hue) in anole radiations from the mountainous Lesser Antillean islands. Adaptation to climatic differences can lead to very pronounced differences between spatially close populations with all studied traits showing some evidence of parallel evolution. Traits from shape, scalation, pattern and hue (particularly the latter) show widespread evolutionary parallels within these species in response to altitudinal climate variation greater than extreme anthropogenic climate change predicted for 2080. This gives strong evidence of the ability to adapt to climate variation by natural selection throughout this radiation. As anoles can evolve very rapidly, it suggests anthropogenic climate change is likely to be less of a conservation threat than other factors, such as habitat loss and invasive species, in this, Lesser Antillean, biodiversity hot spot.