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145 results for “life history variation”
Fig. 2 in Life-history of the South American darter, Characidium pterostictum (Crenuchidae): evidence for small scale spatial variation in a piedmont stream
Fig. 2. Boxplots comparing the total length (Lt) of Characidium pterostictum in Lajeado river (southern Brazil). PA, upstream site; PB downstream site. Numbers in parenthesis are sample size; filled circles are outliers, asterisks are extreme values, dotted line is the mean Lt.
Fig. 1 in Life-history of the South American darter, Characidium pterostictum (Crenuchidae): evidence for small scale spatial variation in a piedmont stream
Fig. 1. Size frequency distribution (total length, Lt) for Characidium pterostictum in two sampling sites at Lajeado river, southern Brazil (PA, n = 62; PB, n = 188).
Data and code from: Variety is the spice of life: nongenetic variation in life histories influences population growth and evolvability
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Data and code from: Seasonal timing of ecosystem linkage mediates life-history variation in a salmonid fish population
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Slower environmental cycles maintain greater life-history variation within populations
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Linking spatial variations in life-history traits to environmental conditions across American black bear populations
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Data from: Cis-regulatory differences in isoform expression associate with life history strategy variation in Atlantic salmon
<p><span><span><span><span><span><span><span><span><span><span><span><b>A major goal in biology is to understand how evolution shapes variation in individual life histories. Genome-wide association studies have been successful in uncovering genome regions linked with traits underlying life history variation in a range of species. However, lack of functional studies of the discovered genotype-phenotype associations severely restrains our understanding how alternative life history traits evolved and are mediated at the molecular level. Here, we report a <i>cis</i>-regulatory mechanism whereby expression of alternative isoforms of the transcription co-factor <i>vestigial-like 3</i> (<i>vgll3</i>) associate with variation in a key life history trait, age at maturity, in Atlantic salmon (<i>Salmo salar</i>). Using a common-garden experiment, we first show that <i>vgll3 </i>genotype associates with puberty timing in one-year-old salmon males. By way of temporal sampling of <i>vgll3 </i>expression in ten tissues across the first year of salmon development, we identify a pubertal transition in <i>vgll3</i> expression where maturation coincided with a 66% reduction in testicular <i>vgll3</i> expression. The <i>late </i>maturation allele was not only associated with a tendency to delay puberty, but also with expression of a rare transcript isoform of <i>vgll3</i> pre-puberty. By comparing absolute <i>vgll3 </i>mRNA copies in heterozygotes we show that the expression difference between the <i>early</i>and <i>late</i> maturity alleles is largely <i>cis</i>-regulatory. We propose a model whereby expression of a rare isoform from the <i>late </i>allele shifts the liability of its carriers towards delaying puberty. These results exemplify the potential importance of regulatory differences as a mechanism for the evolution of life history traits.</b></span></span></span></span></span></span></span></span></span></span></span></p>
Developmental life history is associated with variation in rates of climatic niche evolution in a salamander adaptive radiation
Rates of climatic niche evolution vary widely across the tree of life and are strongly associated with rates of diversification and the accumulation of species diversity among clades. However, why the climatic niche evolves more rapidly in some lineages than others remains unclear. Variation in life history traits often plays a key role in determining the environmental conditions under which species can survive, and therefore, could impact the rate at which lineages can expand in available climatic niche space. Here, we explore the relationships among life-history variation, climatic niche breadth, and rates of climatic niche evolution. We reconstruct a new phylogeny for the genus Desmognathus, an adaptive radiation of salamanders distributed across eastern North America, based on nuclear and mitochondrial genes. Using this phylogeny, we estimate rates of climatic niche evolution for species with long, short, and no aquatic larval stage. Rates of climatic niche evolution are unrelated to the mean climatic niche breadth of species with different life histories. Instead, we find that the evolution of a short larval period promotes greater exploration of climatic space, leading to increased rates of climatic niche evolution across species having this trait. We propose that morphological and physiological differences associated with variation in larval stage length underlie the heterogeneous ability of lineages to explore climatic niche space. Rapid rates of climatic niche evolution among lineages with short larval periods were an important dimension of the clade's adaptive radiation and likely contributed to the rapid rate of lineage accumulation following the evolution of an aquatic life history in this clade. Our results show how variation in a key life-history trait can constrain or promote divergence of the climatic niche, leading to variation in rates of climatic niche evolution among lineages.
Data from: Breeding season length and nest mortality drive cryptic life history variation in Dark-eyed Juncos (Junco hyemalis) breeding across a montane elevation gradient
The manner in which individual life history traits respond to the environment and to each other, and how these traits combine to form overall patterns of life history variation, remains poorly characterized in wild populations. We monitored breeding Dark-eyed Juncos (Junco hyemalis) across a 700-m elevational range. We compared breeding season length, temporal patterns of breeding activity, adult body size, clutch size, brood size, nestling quality, and nest mortality among elevations. We also compared environmental measures across the studied elevations to determine whether abiotic factors explained life history trait variation. We used 12 microsatellite loci to test for genetic differentiation in populations at different elevations. Finally, we constructed a computer simulation to evaluate the combined effects of observed variation in life history traits. We found differences among elevations in breeding season length and in patterns of reproductive timing, which did not match each other and which were not explained solely by abiotic factors. We found no differences among elevations in adult body size, clutch size, brood size, or nestling quality. Nest mortality increased significantly with elevation. Genetic differentiation was too low to define distinct subpopulations. The simulation suggested that differences in mortality, in combination with differences in breeding season length, contributed to substantial differences in reproductive success among elevations. Thus, although individual life history traits showed little evidence of variation in response to the environment or to each other and little genetic differentiation, variation in breeding season length and in nest mortality were potential drivers of substantial elevational variation in overall life history in this system. These results demonstrate that individual life history traits may vary substantially in their patterns of variation, and that some life history traits may have disproportionate effects on overall life history.
Data from: Apparent annual survival estimates of tropical songbirds better reflect life history variation when based on intensive field methods
Aim: Adult survival is central to theories explaining latitudinal gradients in life history strategies. Life history theory predicts higher adult survival in tropical than north temperate regions given lower fecundity and parental effort. Early studies were consistent with this prediction, but standard-effort netting studies in recent decades suggested that apparent survival rates in temperate and tropical regions strongly overlap. Such results do not fit with life history theory. Targeted marking and resighting of breeding adults yielded higher survival estimates in the tropics, but this approach is thought to overestimate survival because it does not sample social and age classes with lower survival. We compared the effect of field methods on tropical survival estimates and their relationships with life history traits. Location: Sabah, Malaysian Borneo. Time period: 2008–2016. Major taxon: Passeriformes. Methods: We used standard-effort netting and resighted individuals of all social and age classes of 18 tropical songbird species over 8 years. We compared apparent survival estimates between these two field methods with differing analytical approaches. Results: Estimated detection and apparent survival probabilities from standard-effort netting were similar to those from other tropical studies that used standard-effort netting. Resighting data verified that a high proportion of individuals that were never recaptured in standard-effort netting remained in the study area, and many were observed breeding. Across all analytical approaches, addition of resighting yielded substantially higher survival estimates than did standard-effort netting alone. These apparent survival estimates were higher than for temperate zone species, consistent with latitudinal differences in life histories. Moreover, apparent survival estimates from addition of resighting, but not from standard-effort netting alone, were correlated with parental effort as measured by egg temperature across species. Main conclusions: Inclusion of resighting showed that standard-effort netting alone can negatively bias apparent survival estimates and obscure life history relationships across latitudes and among tropical species.
Data from: Vertically inherited microbiota and environment modifying behaviors conceal genetic variation in dung beetle life history
<p>Diverse organisms actively manipulate their (sym)biotic and physical environment in ways that feedback on their own development. However, the degree to which these processes affect microevolution remains poorly understood. The gazelle dung beetle both physically modifies its ontogenetic environment and structures its biotic interactions through vertical symbiont transmission. By experimentally eliminating i) physical environmental modifications, and ii) the vertical inheritance of microbes, we assess how environment modifying behavior and microbiome transmission shape heritable variation. We found that depriving larvae from symbionts and environment modifying behaviors increased additive genetic variance and heritability for development time but not body size. This suggests that larvae's ability to manipulate their environment has the potential to modify heritable variation and to facilitate the accumulation of cryptic genetic variation. This cryptic variation may become released and selectable when organisms encounter environments that alter the degree to which they can be manipulated. Furthermore, we found heritable variation for the response to the elimination of environmental modifications, indicating that genotypes differ in their dependence on the ability to manipulate their environment. Our findings highlight that the ability of organisms to actively manipulate their environment may affect the potential of populations to evolve when encountering novel, stressful conditions.</p>
Maternally-transferred thyroid hormones and life-history variation in birds
<p><span>1. In vertebrates, thyroid hormones (THs) play an important role in the regulation of growth, development, metabolism, photoperiodic responses and migration. Maternally transferred THs are important for normal early-phase embryonic development when embryos are not able to produce endogenous THs. Previous studies have shown that variation in maternal THs within the physiological range can influence offspring phenotype.</span></p> <p><span>2. Given the essential functions of maternal THs in development and metabolism, THs may be a mediator of life-history variation across species. </span></p> <p><span>3. We tested the hypothesis that differences in life histories are associated with differences in maternal TH transfer across species. Using birds as a model, we specifically tested whether maternally transferred yolk THs co-vary with migratory status, developmental mode, and traits related to pace-of-life (e.g. basal metabolic rate, maximum lifespan).</span></p> <p><span>4. We collected un-incubated eggs (n = 1-21 eggs per species, median = 7) from 34 wild and captive bird species across 17 families and 6 orders to measure yolk THs (both triiodothyronine, T3 and thyroxine, T4), compiled life-history trait data from the literature, and used Bayesian phylogenetic mixed models to test our hypotheses.</span></p> <p><span>5. Our models indicated that both concentrations and total amounts of the two main forms of THs (T3 and T4) were higher in the eggs of migratory species compared to resident species, and total amounts were higher in the eggs of precocial species, which have longer prenatal developmental periods, than in those of altricial species. However, maternal yolk THs did not show clear associations with pace-of-life related traits, such as fecundity, basal metabolic rate, or maximum lifespan.</span></p> <p><span>6. We quantified interspecific variation in maternal yolk THs in birds and our findings suggest higher maternal TH transfer is associated with the precocial mode of development and migratory status. Whether maternal THs represent a part of the mechanism underlying the evolution of precocial development and migration or a consequence of such life histories is currently unclear. We therefore encourage further studies to explore the physiological mechanisms and evolutionary processes underlying these patterns.</span></p>
Chipmunk body mass variations and life-histories in a pulsed resource ecosystem
<p><span>Phenotypic plasticity is the most immediate mechanism of adaptative response to environmental change. Studying plastic changes in response to fluctuating environments provides insights into how such adjustments may impact life-history traits. Here, we used a 14-year dataset of repeated body mass measurements in male eastern chipmunks (<em>Tamias striatus</em>) to assess the extent of plastic changes for this trait in a resource pulse ecosystem. We first determined the magnitude of variation in body mass at the population level in response to the drastic change in food resource availability from American beech tree seeds (<em>Fagus grandifolia</em>). Males that emerged in the spring from winter torpor following a non-mast year had a lower body mass than males emerging after a mast year, but they tended to recover this loss by mid-June. We found significant among-individual variation in spring body mass plasticity (i.e., individual by environment interaction, I x E). We then investigated the relationships between individual spring body mass plasticity, longevity and lifetime reproductive success. Interestingly, heavier males lived longer than lighter males, but more plastic males had a lower longevity and lower lifetime reproductive success than less plastic males. The report of such plastic response in a stochastic resource system provides valuable insights into the interplay between the costs and benefits of phenotypic plasticity as an adaptation to environmental fluctuations.</span></p>
Variation and plasticity in life-history traits and fitness of wild Arabidopsis thaliana populations are not related to their genotypic and ecological diversity
<p>Despite its implications for population dynamics and evolution, the relationship between genetic and phenotypic variation in wild populations remains unclear. Here, we estimated variation and plasticity in life-history traits and fitness of the annual plant <em>Arabidopsis thaliana</em> in two common garden experiments that differed in environmental conditions. We used up to 306 maternal inbred lines from six Iberian populations characterized by low and high genotypic (based on whole-genome sequences) and ecological (vegetation type) diversity. Low and high genotypic and ecological diversity was found in edge and core Iberian environments, respectively. Given that selection is expected to be stronger in edge environments and that ecological diversity may enhance both phenotypic variation and plasticity, we expected genotypic diversity to be positively associated with phenotypic variation and plasticity. However, maternal lines, irrespective of the genotypic and ecological diversity of their population of origin, exhibited a substantial amount of phenotypic variation and plasticity for all traits. Furthermore, all populations harbored maternal lines with canalization (robustness) or sensitivity in response to harsher environmental conditions in one of the two experiments. Overall, we conclude that the environmental attributes of each population probably determine their genotypic diversity, but all populations maintain substantial phenotypic variation and plasticity for all traits, which represents an asset to endure in changing environments.</p>
Data from: Phenotypically plastic responses to environmental variation are more complex than life history theory predicts
<p>For insects that exhibit wing polyphenic development, abiotic and biotic signals dictate the adult wing morphology of the insect in an adaptive manner such that in stressful environments the formation of a flight-capable morph is favored and in low stress environments a flightless morph is favored. While there is a relatively large amount known about the environmental cues that dictate morph formation in wing polyphenic hemipterans like planthoppers and aphids, whether those cues dictate the same morphs in non-hemipteran (i.e. cricket) wing polyphenic species has not been explicitly investigated. To experimentally test the generality of environmental cue determination of wing polyphenism across taxa with diverse life histories, in this study we tested the importance of food quantity, parasitic infection, and tactile cues on wing morph determination in the wing polyphenic sand field cricket, <em>Gryllus firmus</em>. Our results also show that certain stress cues, such as severe diet quantity limitation and parasitic infection, actually led to an increase in the production of flightless morph. Based on these findings, our results suggest that physiological and genetic constraints are important to an organism's ability to respond to environmental variation in an adaptive manner beyond simple life history trade-offs.</p>
Data from: Among-species variation in six decades of changing migration timings explained through ecology, life-history and abundance
<p>Species utilising seasonal environments must now alter timings of key life-history events in response to large-scale climatic changes, thereby maintaining trophic synchronies. Yet substantial among-species variation in cross-decadal phenological changes is observed. Transitioning from basic description of such variation towards prediction of future phenological responses now requires standardised studies that rigorously quantify and explain variation in the direction, magnitude and form of changing timings across diverse species in relation to key ecological and life-history variables. Accordingly, we fitted multi-quantile regressions to 59 years of high-quality multi-species data on spring and autumn bird migration timings through northern Scotland. We demonstrate substantial variation in cross-decadal changes in timings among 72 species, and quantify the degree to which variation can be explained through differences in species ecology, life-history and population trajectories. Consistent with predictions, species with seasonal diets, narrower breeding habitat breadths, shorter generation lengths and capability to produce multiple offspring broods per year advanced their migration timing in one or both seasons. In contrast, species with less seasonal diets, and that produce single annual offspring broods, showed no change. Meanwhile, contrary to prediction, long-distance migrants advanced their migration timings as much as short-distance migrants. Changes in migration timing also varied with changes in local migratory abundance, such that species with increasing seasonal abundance apparently altered their migration timing, whilst species with decreasing abundance did not. These patterns concur with expectation if changing migration timing is adaptive. However, we demonstrate that similar patterns can be generated through numerical sampling processes given changing abundances, implying that apparent phenology-abundance relationships should be carefully validated and interpreted. Overall, our results show that migrant bird species with differing ecologies and life-histories have shown systematically differing phenological changes over six decades contextualised by large-scale environmental changes, potentially facilitating future predictions and altering temporal dynamics of seasonal species co-occurrences.</p>
Data from: Evolutionary variation in gene conversion at the avian MHC is explained by fluctuating selection, gene copy numbers, and life history
<p>The Major Histocompatibility Complex (MHC) multigene family encodes key pathogen-recognition molecules of the vertebrate adaptive immune system. Hyper-polymorphism of MHC genes is <em>de novo</em> generated by point mutations, but new haplotypes may also arise by re-shuffling of existing variation through intra- and inter-locus gene conversion. Although the occurrence of gene conversion at the MHC has been known for decades, we still have limited understanding of its functional importance. Here, I took advantage of extensive genetic resources (~9000 sequences) to investigate a broad scale macroevolutionary patterns in gene conversion processes at the MHC across nearly 200 avian species. Gene conversion was found to constitute a universal mechanism in birds, as 83% of species showed footprints of gene conversion at either MHC class and 25% of all allelic variants were attributed to gene conversion. Gene conversion processes were stronger at MHC-II than MHC-I, but inter-specific variation at both MHC classes was explained by similar evolutionary scenarios, reflecting fluctuating selection towards different optima and drift. Gene conversion showed uneven phylogenetic distribution across birds and was driven by gene copy number variation, supporting significant role of inter-locus gene conversion processes in the evolution of the avian MHC. Finally, MHC gene conversion was stronger in species with fast life histories (high fecundity) and in long-distance migrants, likely reflecting variation in population sizes and host-pathogen coevolutionary dynamics. The results provide a robust comparative framework for understanding macroevolutionary variation in gene conversion at the avian MHC and reinforce important contribution of this mechanism to functional MHC diversity.</p>
Ontogenetic variation in the marine foraging of Atlantic salmon functionally links genomic diversity with a major life history polymorphism
<p>The ecological role of heritable phenotypic variation in free-living populations remains largely unknown. Knowledge of the genetic basis of functional ecological processes can link genomic and phenotypic diversity, providing insight into polymorphism evolution and how populations respond to environmental change. By quantifying the marine diet, of sub-adult Atlantic salmon, we assessed how foraging behavior changes along the ontogeny, and in relation to genetic variation in two loci with major effect on age-at-maturity (<em>six6</em> and <em>vgll3</em>). We used a two-component, zero-inflated negative binomial model to simultaneously quantify foraging frequency (zero-inflation components) and foraging outcome (count component), separately for fish and crustaceans in the diet. We found that older salmon forage for both prey types more actively (as evidenced by increased foraging frequency), but with a decreased efficiency (as evidenced by fewer prey items in the diet), suggesting an age-dependent shift in foraging dynamics. The <em>vgll3</em> locus was linked to age-dependent changes in foraging behavior: younger salmon with <em>vgll3<sup>LL</sup></em> (the genotype associated with late maturation) tend to forage crustaceans more often than those with <em>vgll3<sup>EE</sup></em> (the<em> </em>genotype associated with early maturation), while the pattern was reversed in older salmon. <em>Vgll3<sup> LL</sup></em> genotype was also linked to marginal increase in fish acquisition especially in younger salmon, while <em>six6</em> was not a factor explaining the diet variation. Our results suggest a functional role for variation in marine feeding behavior linking genomic diversity at <em>vgll3</em> with age-at-maturity among salmon, with potential age-dependent trade-offs maintaining the genetic variation. A shared genetic basis between dietary ecology and age-at-maturity likely subjects Atlantic salmon populations to evolution induced by bottom-up changes in marine productivity.</p>
Data from: Genomic differentiation during speciation-with-gene-flow: comparing geographic and host-related variation in divergent life history adaptation in Rhagoletis pomonella
A major goal of evolutionary biology is to understand how variation within populations gets partitioned into differences between reproductively isolated species. Here, we examine the degree to which diapause life history timing, a critical adaptation promoting population divergence, explains geographic and host-related genetic variation in ancestral hawthorn and recently derived apple-infesting races of Rhagoletis pomonella. Our strategy involved combining experiments on two different aspects of diapause (initial diapause intensity and adult eclosion time) with a geographic survey of genomic variation across four sites where apple and hawthorn flies co-occur from north to south in the Midwestern USA. The results demonstrated that the majority of the genome showing significant geographic and host-related variation can be accounted for by initial diapause intensity and eclosion time. Local genomic differences between sympatric apple and hawthorn flies were subsumed within broader geographic clines; allele frequency differences within the races across the Midwest were 2 to 3-fold greater than those between the races in sympatry. As a result, sympatric apple and hawthorn populations displayed more limited genomic clustering compared to geographic populations within the races. The findings suggest that with reduced gene flow and increased selection on diapause equivalent to that seen between geographic sites, the host races may be recognized as different genotypic entities in sympatry, and perhaps species, a hypothesis requiring future genomic analysis of related sibling species to R. pomonella to test. Our findings concerning the way selection and geography interplay could be of broad significance for many cases of earlier stages of divergence-with-gene flow, including (1) where only modest increases in geographic isolation and the strength of selection may greatly impact genetic coupling and (2) the dynamics of how spatial and temporal standing variation is extracted by selection to generate differences between new and discrete units of biodiversity.
Data from: Life history variation in an invasive plant is associated with climate and recent colonization of a specialist herbivore
<p><b>Premise:</b> Spatial variation in selective pressures can lead to intraspecific variation in life history, favoring some life histories and constraining others depending on the vulnerability of life stages. We examined how spatial variation in herbivory and climate influences flowering size and the occurrence of semelparity (reproducing once) versus iteroparity (reproducing multiple times) in the introduced range of an invasive plant, houndstongue (<i>Cynoglossum officinale</i>). Houndstongue is a short-lived semelparous perennial in its native range. In its introduced range, we previously documented increased rates of iteroparity and a higher median threshold flowering size compared to the native range. We hypothesized that the recent introduction of a specialist biocontrol insect (a root-boring weevil, <i>Mogulones crucifer</i>) would decrease threshold flowering size, and reduce the proportion of iteroparous plants, because <i>M. crucifer</i> preferentially attacks large individuals and may reduce overwinter survival.</p> <p><b>Methods:</b> We surveyed 24 sites across the northwestern United States to quantify the frequency of semelparity versus iteroparity and to estimate weevil abundance, and used demographic data collected from six sites to estimate median threshold flowering size.</p> <p><b>Key Results</b>: We found that sites with greater winter precipitation and no weevils had a greater proportion of iteroparous plants. Sites with higher weevil attack had a lower median threshold flowering size.</p> <p><b>Conclusions:</b> The variation in frequency of flowering and threshold flowering size that we documented in North American houndstongue populations and the relationships between this variation and herbivory and climate provide evidence for how selective pressures covary with the life histories of invasive plants.</p>
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Allen Brain Atlas
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The International Brain Laboratory public data releases expose standardized mouse decision-making experiments, including Neuropixels recordings, widefield calcium imaging, behavior, and session metadata accessed through the ONE API.
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