首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 15 毫秒
1.
    
In temperate climates, the recurring seasonal exigencies of winter represent a fundamental physiological challenge for a wide range of organisms. In response, many temperate insects enter diapause, an alternative developmental program, including developmental arrest, that allows organisms to synchronize their life cycle with seasonal environmental variation. Geographic variation in diapause phenology contributing to local climatic adaptation is well documented. However, few studies have examined how the rapid evolution of a suite of traits expressed across the diapause program may contribute to climatic adaptation on a contemporary timescale. Here, we investigate the evolution of the diapause program over the past 35 years by leveraging a “natural experiment” presented by the recent invasion of the Asian tiger mosquito, Aedes albopictus, across the eastern United States. We sampled populations from two distinct climatic regions separated by 6° of latitude (∼700 km). Using common-garden experiments, we identified regional genetic divergence in diapause-associated cold tolerance, diapause duration, and postdiapause starvation tolerance. We also found regional divergence in nondiapause thermal performance. In contrast, we observed minimal regional divergence in nondiapause larval growth traits and at neutral molecular marker loci. Our results demonstrate rapid evolution of the diapause program and imply strong selection caused by differences in winter conditions.  相似文献   

2.
    
Acacia karroo Hayne (Mimosoideae; Fabaceae) is a highly polymorphic species, ranging in height from 1 m to more than 30 m, and with enormous variation in the architecture of adults. Some populations of A. karroo with different morphologies are situated less than 20 km apart. This species has been considered to be a ring species on the basis of allozyme variation. I wished to determine whether this was supported by sapling morphology, and by chemical and physical defences to herbivory. I raised four phenotypes from the restricted area of Zululand (South Africa) in a common garden with controls, and with water and nutrient supplementation. I found that each of the four phenotypes maintained their differences in spite of nutrient and water supplementation. There was no significant genotype by environment interaction. I also found that the coastal population was significantly larger than another phenotype that grows just 12 km inland from it, suggesting that there might be local adaptation of these genotypes to particular soil types. I confirm that A. karroo maintains morphological differentiation even when there is substantial alteration of water and nutrient availability. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 748–755.  相似文献   

3.
    
Oxygen conductance to the tissues determines aerobic metabolic performance in most eukaryotes but has cost/benefit tradeoffs. Here we examine in lowland populations of a butterfly a genetic polymorphism affecting oxygen conductance via the hypoxia‐inducible factor (HIF) pathway, which senses intracellular oxygen and controls the development of oxygen delivery networks. Genetically distinct clades of Glanville fritillary (Melitaea cinxia) across a continental scale maintain, at intermediate frequencies, alleles in a metabolic enzyme (succinate dehydrogenase, SDH) that regulates HIF‐1α. One Sdhd allele was associated with reduced SDH activity rate, twofold greater cross‐sectional area of tracheoles in flight muscle, and better flight performance. Butterflies with less tracheal development had greater post‐flight hypoxia signaling, swollen & disrupted mitochondria, and accelerated aging of flight metabolic performance. Allelic associations with metabolic and aging phenotypes were replicated in samples from different clades. Experimentally elevated succinate in pupae increased the abundance of HIF‐1α and expression of genes responsive to HIF activation, including tracheal morphogenesis genes. These results indicate that the hypoxia inducible pathway, even in lowland populations, can be an important axis for genetic variation underlying intraspecific differences in oxygen delivery, physiological performance, and life history.  相似文献   

4.
    
Cosmopolitan populations of Drosophila melanogaster have co‐opted a form of reproductive diapause to overwinter in northern populations. Polymorphism in the couch potato gene has been implicated in genetic variation for this diapause trait. Using a collection of 20 populations from Florida to Canada and 11 collections from 3 years in a Pennsylvania orchard, we estimated the allele frequencies for 15 single nucleotide polymorphisms (SNPs) in the couch potato gene. These include the specific polymorphism associated with diapause inducability. We find that the SNP polymorphism, 48034(A/T), is correlated with latitude and its frequencies are predicted by the incidence of diapause trait. We find that the clinal patterns for cpo SNPs sampled in 1997 are similar to the same SNPs sampled in 2009–2010. SNPs that show apparent associations with cpo expression are also clinal with the low‐expression allele increasing in frequency, as would be predicted from functional knockout studies of cpo. Finally, we see a significant pattern where the frequency of the diapause‐causing allele drops in frequency during the summer season, consistent with the drop in the incidence of the diapause trait. The selection required to drive this response is large, roughly 24% to 59% per generation depending on the degree of dominance.  相似文献   

5.
    
Many ectotherms show crossing growth trajectories as a plastic response to rearing temperature. As a result, individuals growing up in cool conditions grow slower, mature later, but are larger at maturation than those growing up in warm conditions. To date, no entirely satisfactory explanation has been found for why this pattern, often called the temperature‐size rule, should exist. Previous theoretical models have assumed that size‐specific mortality rates were most likely to drive the pattern. Here, I extend one theoretical model to show that variation in size‐fecundity relationships may also be important. Plasticity in the size‐fecundity relationship has rarely been considered, but a number of studies show that fecundity increases more quickly with size in cold environments than it does in warm environments. The greater increase in fecundity offsets costs of delayed maturation in cold environments, favoring a larger size at maturation. This can explain many cases of crossing growth trajectories, not just in relation to temperature.  相似文献   

6.
    
Recent progress in methods for detecting adaptive population divergence in situ shows promise for elucidating the conditions under which selection acts to generate intraspecific diversity. Rapid ecological diversification is common in fishes; however, the role of phenotypic plasticity and adaptation to local environments is poorly understood. It is now possible to investigate genetic patterns to make inferences regarding phenotypic traits under selection and possible mechanisms underlying ecotype divergence, particularly where similar novel phenotypes have arisen in multiple independent populations. Here, we employed a bottom‐up approach to test for signatures of directional selection associated with divergence of beach‐ and stream‐spawning kokanee, the obligate freshwater form of sockeye salmon (Oncorhynchus nerka). Beach‐ and stream‐spawners co‐exist in many post‐glacial lakes and exhibit distinct reproductive behaviours, life‐history traits and spawning habitat preferences. Replicate ecotype pairs across five lakes in British Columbia, Canada were genotyped at 57 expressed sequence tag‐linked and anonymous microsatellite loci identified in a previous genome scan. Fifteen loci exhibited signatures of directional selection (high FST outliers), four of which were identified in multiple lakes. However, the lack of parallel genetic patterns across all lakes may be a result of: 1) an inability to detect loci truly under selection; 2) alternative genetic pathways underlying ecotype divergence in this system; and/or 3) phenotypic plasticity playing a formative role in driving kokanee spawning habitat differences. Gene annotations for detected outliers suggest pathogen resistance and energy metabolism as potential mechanisms contributing to the divergence of beach‐ and stream‐spawning kokanee, but further study is required.  相似文献   

7.
    
We carried out a three‐tiered genetic analysis of egg‐to‐adult development time and viability in ancestral and derived populations of cactophilic Drosophila mojavensis to test the hypothesis that evolution of these life‐history characters has shaped premating reproductive isolation in this species. First, a common garden experiment with 11 populations from Baja California and mainland Mexico and Arizona reared on two host species revealed significant host plant X region and population interactions for viability and development time, evidence for host plant adaptation. Second, replicated line crosses with flies reared on both hosts revealed autosomal, X chromosome, cytoplasmic, and autosome X cactus influences on development time. Viability differences were influenced by host plants, autosomal dominance, and X chromosomal effects. Many of the F1, F2, and backcross generations showed evidence of heterosis for viability. Third, a QTL analysis of male courtship song and epicuticular hydrocarbon variation based on 1688 Baja × mainland F2 males also revealed eight QTL influencing development time differences. Mainland alleles at six of these loci were associated with longer development times, consistent with population‐level differences. Eight G × E interactions were also detected caused by longer development times of mainland alleles expressed on a mainland host with smaller differences among Baja genotypes reared on the Baja host plant. Four QTL influenced both development time and epicuticular hydrocarbon differences associated with courtship success, and there was a significant QTL‐based correlation between development time and cuticular hydrocarbon variation. Thus, the regional shifts in life histories that evolved once D. mojavensis invaded mainland Mexico from Baja California by shifting host plants were genetically correlated with variation in cuticular hydrocarbon‐based mate preferences.  相似文献   

8.
  总被引：3，自引：0，他引：3  
Although a considerable amount of information is available on the ecology, genetics, and physiology of life-history traits, much more limited data are available on the biochemical and genetic correlates of life-history variation within species. Specific activities of five enzymes of lipid biosynthesis and two enzymes of amino acid catabolism were compared among lines selected for flight-capable (LW[f]) versus flightless (SW) morphs of the cricket Gryllus firmus. These morphs, which exist in natural populations, differ genetically in ovarian growth (100-400% higher in SW) and aspects of flight capability including the size of wings and flight muscles, and the concentration of triglyceride flight fuel (40% greater in LW[f]). Consistently higher activity of each enzyme in LW(f) versus SW-selected lines, and strong co-segregation between morph and enzyme activity, demonstrated genetically based co-variance between wing morph and enzyme activity. Developmental profiles of enzyme activities strongly paralleled profiles of triglyceride accumulation during adulthood and previous measures of in vivo lipid biosynthesis. These data strongly imply that genetically based elevation in activities of lipogenic enzymes, and enzymes controlling the conversion of amino acids into lipids, is an important cause underlying the elevated accumulation of triglyceride in the LW(f) morph, a key biochemical component of the trade-off between elevated early fecundity and flight capability. Global changes in lipid and amino-acid metabolism appear to have resulted from microevolutionary alteration of regulators of metabolism. Finally, strong genotype x environment (diet) interactions were observed for most enzyme activities. Future progress in understanding the functional causes of life-history evolution requires a more detailed synthesis of the fields of life-history evolution and metabolic biochemistry. Wing polymorphism is a powerful experimental model in such integrative studies.  相似文献   

9.
    
Expansion of the host range in phytophagous insects depends on their ability to form an association with a novel plant through changes in host‐related traits. Phenotypic plasticity has important effects on initial survival of individuals faced with a new plant, as well as on the courses of evolutionary change during long‐term adaptation to novel conditions. Using experimental populations of the seed beetle that evolved on ancestral (common bean) or novel (chickpea) host and applying reciprocal transplant at both larval and adult stage on the alternative host plant, we studied the relationship between the initial (plastic) phases of host‐shift and the subsequent stages of evolutionary divergence in life‐history strategies between populations exposed to the host‐shift process. After 48 generations, populations became well adapted to chickpea by evolving the life‐history strategy with prolonged larval development, increased body mass, earlier reproduction, shorter lifespan and decreased plasticity of all traits compared with ancestral conditions. In chickpea‐adapted beetles, negative fitness consequences of low plasticity of pre‐adult development (revealed as severe decrease in egg‐to‐adult viability on beans) exhibited mismatch with positive effects of low plasticity (i.e. low host sensitivity) in oviposition and fecundity. In contrast, beetles adapted to the ancestral host showed high plasticity of developmental process, which enabled high larval survival on chickpea, whereas elevated plasticity in adult behaviour (i.e. high host sensitivity) resulted in delayed reproduction and decreased fecundity on chickpea. The analysis of population growth parameters revealed significant fluctuation during successive phases of the host‐shift process in A. obtectus.  相似文献   

10.
五角枫种群表型多样性   总被引：6，自引：2，他引：6       下载免费PDF全文
为揭示五角枫种群的表型分化程度、变异模式及地理变异规律,以山西19个种群为研究对象,采用巢式方差分析、相关分析、聚类分析等方法从形态学角度对五角枫种群的叶片、果实、种子等23个表型性状进行了系统分析。结果表明:(1)五角枫23个表型性状中除果柄长、着生痕、种子长/宽以外,其余20个表型性状在种群间和种群内均存在显著和极显著差异。(2)19个种群的平均变异系数为18.07。叶片、果实、种子的平均表型变异系数依次为:果实19.78%叶片18.77%种子10.25%。(3)五角枫种群间表型分化系数(VST)均值为48.82%,种群内变异(51.18%)与种群间变异(48.82%)基本相当。叶片、果实、种子表型分化系数的平均值为:叶片58.08%果实41.24%种子25.87%。(4)五角枫叶片、果实和种子的信息多样性指数(H)为:叶片6.1079果实5.9118种子5.2855;多样性指数平均值(D)分别为:果实0.9967叶片0.9961种子0.9948。(5)主成分分析结果显示:五角枫种群表型多样性基本来源为:叶片贡献率果实贡献率种子贡献率。(6)五角枫表型变异呈现出以经度和纬度变异并存的趋势,少数表型性状与经度和纬度呈现显著或极显著相关。(7)利用欧氏距离对五角枫种群进行UPGMA聚类分析,将五角枫19个种群划分为两大类群。五角枫种群具有较高的表型多样性,种群间和种群内均存在丰富的表型变异,与其遗传特点和分布生境等密切相关,研究结果为今后五角枫种质资源的保护和利用奠定了基础。  相似文献   

11.
Many studies in human genetics compare informativeness of single‐nucleotide polymorphisms (SNPs) and microsatellites (single sequence repeats; SSR) in genome scans, but it is difficult to transfer the results directly to livestock because of different population structures. The aim of this study was to determine the number of SNPs needed to obtain the same differentiation power as with a given standard set of microsatellites. Eight chicken breeds were genotyped for 29 SSRs and 9216 SNPs. After filtering, only 2931 SNPs remained. The differentiation power was evaluated using two methods: partitioning of the Euclidean distance matrix based on a principal component analysis (PCA) and a Bayesian model‐based clustering approach. Generally, with PCA‐based partitioning, 70 SNPs provide a comparable resolution to 29 SSRs. In model‐based clustering, the similarity coefficient showed significantly higher values between repeated runs for SNPs compared to SSRs. For the membership coefficients, reflecting the proportion to which a fraction segment of the genome belongs to the ith cluster, the highest values were obtained for 29 SSRs and 100 SNPs respectively. With a low number of loci (29 SSRs or ≤100 SNPs), neither marker types could detect the admixture in the Gödöllö Nhx population. Using more than 250 SNPs allowed a more detailed insight into the genetic architecture. Thus, the admixed population could be detected. It is concluded that breed differentiation studies will substantially gain power even with moderate numbers of SNPs.  相似文献   

12.
    
A recent study suggests that postdauer Caenorhabditis elegans hermaphrodites produce more self‐sperm and have larger brood sizes than worms that bypass diapause. Why might natural selection favor increased self‐sperm production in postdauer hermaphrodites? This question is addressed by developing an age‐structured model for an exponentially growing worm population descending from a founder postdauer hermaphrodite. It is assumed that natural selection favors those founders that have the largest number of living descendants at some fixed future time. Increased self‐sperm production in postdauer hermaphrodites can then evolve when the diapause‐bypassing descendants suffer a higher mortality rate than their parental postdauer founders.  相似文献   

13.
    
Eight dinucleotide microsatellite loci were developed through an enrichment protocol for allis shad (Alosa alosa) and twaite shad (A. fallax). Cross‐species amplification was successful for all loci isolated. The number of alleles per locus ranged from three to nine for A. alosa and from two to seven for A. fallax, while the observed heterozygosity ranged from 0.267 to 0.926 and from 0.240 to 0.727, respectively. These markers will constitute useful tools for studies of population structure and gene flow between two closely related hybridizing species.  相似文献   

14.
Genetic Diversity and the Survival of Populations   总被引：7，自引：0，他引：7  
Abstract: In this comprehensive review, a range of factors is considered that may influence the significance of genetic diversity for the survival of a population. Genetic variation is essential for the adaptability of a population in which quantitatively inherited, fitness-related traits are crucial. Therefore, the relationship between genetic diversity and fitness should be studied in order to make predictions on the importance of genetic diversity for a specific population. The level of genetic diversity found in a population highly depends on the mating system, the evolutionary history of a species and the population history (the latter is usually unknown), and on the level of environmental heterogeneity. An accurate estimation of fitness remains complex, despite the availability of a range of direct and indirect fitness parameters. There is no general relationship between genetic diversity and various fitness components. However, if a lower level of heterozygosity represents an increased level of inbreeding, a reduction in fitness can be expected. Molecular markers can be used to study adaptability or fitness, provided that they represent a quantitative trait locus (QTL) or are themselves functional genes involved in these processes. Next to a genetic response of a population to environmental change, phenotypic plasticity in a genotype can affect fitness. The relative importance of plasticity to genetic diversity depends on the species and population under study and on the environmental conditions. The possibilities for application of current knowledge on genetic diversity and population survival for the management of natural populations are discussed.  相似文献   

15.
    
Experimental evolution (EE) is a powerful tool for addressing how environmental factors influence life‐history evolution. While in nature different selection pressures experienced across the lifespan shape life histories, EE studies typically apply selection pressures one at a time. Here, we assess the consequences of adaptation to three different developmental diets in combination with classical selection for early or late reproduction in the fruit fly Drosophila melanogaster. We find that the response to each selection pressure is similar to that observed when they are applied independently, but the overall magnitude of the response depends on the selection regime experienced in the other life stage. For example, adaptation to increased age at reproduction increased lifespan across all diets; however, the extent of the increase was dependent on the dietary selection regime. Similarly, adaptation to a lower calorie developmental diet led to faster development and decreased adult weight, but the magnitude of the response was dependent on the age‐at‐reproduction selection regime. Given that multiple selection pressures are prevalent in nature, our findings suggest that trade‐offs should be considered not only among traits within an organism, but also among adaptive responses to different—sometimes conflicting—selection pressures, including across life stages.  相似文献   

16.
Algae hold promise as a source of biofuel. Yet, the manner in which algae are most efficiently propagated and harvested is different from that used in traditional agriculture. In theory, algae can be grown in continuous culture and harvested frequently to maintain high yields with a short turnaround time. However, the maintenance of the population in a state of continuous growth will likely impose selection for fast growth, possibly opposing the maintenance of lipid stores desirable for fuel. Any harvesting that removes a subset of the population and leaves the survivors to establish the next generation may quickly select traits that escape harvesting. An understanding of these problems should help identify methods for retarding the evolution and enhancing biofuel production.  相似文献   

17.
Chinook salmon, Oncorhynchus tshawytscha, from the Sacramento River, California, USA were introduced to New Zealand between 1901 and 1907, and colonized most of their present-day range within about 10 years. The New Zealand populations now vary in phenotypic traits typically used to differentiate salmon populations within their natural range: growth in freshwater and at sea, age at maturity, dates of return to fresh water and reproduction, morphology, and reproductive allocation. This paper reviews a large research program designed to determine the relative contributions of phenotypic plasticity and genetic adaptation to this variation, in an effort to understand the processes underlying the natural evolution of new populations. We found strong evidence of trait divergence between populations within at most 30 generations, particularly in freshwater growth rate, date of return, and reproductive output, with plausible adaptive bases for these differences. Importantly, we also demonstrated not only a genetic basis for post-release survival but higher survival, and hence fitness, of a population released from its established site compared to another population released from the same site. We conclude that divergence of salmon in different rivers probably resulted initially from phenotypic plasticity (e.g., habitat-specific growth rates, and effects of upriver migration on ovarian investment). Philopatry (homing to natal streams) combined with rapid evolution of distinct breeding periods to restrict gene flow, facilitating divergence in other traits. We also suggest that in addition to genetic divergence resulting from random founder effects, divergence may also arise during the very early stages of colonization when the original colonists are a non-random, pre-adapted subset of the source population. This favored founders effect immediately improves the fitness of the new population. Overall, this research reveals the complex interplay of environmental and genetic controls over behavior, physiology and life history that characterize the early stages of population differentiation, a process that has taken place repeatedly during the history of salmon populations.  相似文献   

18.
    
Specialization and concomitant trade‐offs are assumed to underlie the non‐neutral coexistence of lineages. Trade‐offs across heterogeneous environments can promote diversity by preventing competitive exclusion. However, the importance of trade‐offs in maintaining diversity in natural microbial assemblages is unclear, as trade‐offs are frequently not detected in artificial evolution experiments. Stressful conditions associated with patches of heavy‐metal enriched serpentine soils provide excellent opportunities for examining how heterogeneity may foster genetic diversity. Using a spatially replicated design, we demonstrate that rhizobium bacteria symbiotic with legumes inhabiting contrasting serpentine and nonserpentine soils exhibit a trade‐off between a genotype's nickel tolerance and its ability to replicate rapidly. Furthermore, we detected adaptive divergence in rhizobial assemblages across soil type heterogeneity at multiple sites, suggesting that this trade‐off may promote the coexistence of phenotypically distinct bacterial lineages. Trade‐offs and adaptive divergence may be important factors maintaining the tremendous diversity within natural assemblages of bacteria.  相似文献   

19.
    
Several species of the diatom Pseudo‐nitzschia produce the neurotoxin domoic acid (DA). Consumption of fish and shellfish that have accumulated this potent excitotoxin has resulted in severe illness and even death in humans, marine mammals, and seabirds. Pseudo‐nitzschia pungens (Grunow ex Cleve) Hasle is a cosmopolitan diatom commonly occurring in the waters of the Pacific Northwest (PNW) and the eastern North Atlantic, including the North Sea. However, genetic and physiological relationships among populations throughout this large geographic distribution have not been assessed. Population genetic parameters (e.g., Hardy–Weinberg equilibrium, linkage equilibrium, FST) calculated for P. pungens collected from the Juan de Fuca eddy region in the PNW indicated the presence of two distinct groups that were more divergent from each other than either was from a P. pungens sample from the North Sea. Geographic heterogeneity was also detected within each of the two PNW groups. These results suggested that the populations of P. pungens recently mixed in the Juan de Fuca eddy region (a seasonally retentive feature off the coasts of Washington State, USA, and Vancouver Island, Canada) but did not exchange genetic material by sexual reproduction. Alternatively, these two groups may be cryptic (morphologically identical, but reproductively isolated) species. Identifying cryptic diversity in Pseudo‐nitzschia is important for bloom prediction and aiding the identification of molecular markers that can be used for rapid detection assay development.  相似文献   

20.
    
Bovine microsatellites were used to amplify DNA of red deer ( Cervus elaphus ). Fourteen of 27 bovine systems (52%) displayed polymorphism, while no (CA)n-repeat was detected in seven systems and six systems gave no amplificates in red deer. The allele number ranged from 2 to 7, the polymorphism information content between 0.24 and 0.76. The results demonstrate that transfer of microsatellite systems between families of the same order (artiodactyla) is possible. Molecular genetic research will help to clarify the differentiation and ecology of wild animals and will contribute to define criteria needed for the preservation of endangered species.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号