Influence of genetic architecture on contemporary local evolution in the soapberry bug,Jadera haematoloma: artificial selection on beak length

Little is known about the influence of genetic architecture on local adaptation. We investigated the genetic architecture of the rapid contemporary evolution of mouthparts, the flight polymorphism and life history traits in the soapberry bug Jadera haematoloma (Hemiptera) using laboratory selection. The mouthparts of these seed‐feeding bugs have adapted in 40–50 years by decreasing in length following novel natural selection induced by a host switch to the seeds of an introduced tree with smaller fruits than those of the native host vine. Laboratory selection on beak length in both an ancestral population feeding on the native host and a derived population feeding on the introduced host reveals genetic variance allowing a rapid response (heritabilities of 0.51–0.87) to selection for either longer or shorter beaks. This selection resulted in reverse evolution by restoring long beaks in the derived population and forward evolution by re‐creating short beaks in the ancestral bugs. There were strong genetic correlations (0.68–0.84) in both populations between beak lengths and the frequency of flight morphs, with short beaks associated with short wings. The results reveal a genetically interrelated set of adaptive multivariate traits including both beak length and flight morph. This suite of traits reflects host plant patchiness and seeding phenology. Weaker evidence suggests that egg mass and early egg production may be elements of the same suite. Reversible or forward evolution thus may occur in a broad set of genetically correlated multivariate traits undergoing rapid contemporary adaptation to altered local environments.     

A test of adaptive divergence in a newly discovered host association of the soapberry bug Jadera haematoloma on Mexican buckeye,Ungnadia speciosa

Host races represent an important step in the speciation process of phytophagous insects as they reflect the maintenance of genetically divergent host-associated populations in the face of appreciable gene flow. The red-shouldered soapberry bug, Jadera haematoloma (Herrich-Schäffer) (Hemiptera: Rhopalidae), is an oligophagous seed predator with a history of host race evolution on plant associations in the (soapberry) family Sapindaceae. Soapberry bugs are a model group for understanding rapid ecological adaptation to their hosts, and hence good candidates for investigating evolutionary divergence in host associations over short timescales. Here, we describe the recent discovery of Mexican buckeye, Ungnadia speciosa Endl., as a host of J. haematoloma in a region of the Chihuahuan desert including west Texas and southeastern New Mexico, USA. This host differs from J. haematoloma’s previously recorded hosts in the Sapindaceae in seed chemistry, ecology, and phylogeny. The tendency toward rapid, host-associated adaptations by populations of J. haematoloma and the unique biology of the newly discovered Ungnadia host create the opportunity for potential host race formation, as it overlaps geographically with two previously recorded host plants in this region – the native western soapberry tree, Sapindus saponaria var. drummondii (Hook & Arn.), and the non-native goldenrain tree, Koelreuteria paniculata Laxm. We explore the possibility of host race formation on Ungnadia-associated insects by testing for host-associated differentiation in morphology and feeding behaviors. We find evidence of differentiation in the length of the mouth parts, which is an ecologically relevant feeding trait between host plant species with larger or smaller seed capsules. This divergence is maintained in the face of potential gene flow by reproductive isolation in the form of habitat isolation, which we detect in host preference trials. Together, our results demonstrate that soapberry bugs associated with this newly discovered host exhibit morphological and behavioral traits consistent with host race formation, but additional work is required to confirm its state along the speciation continuum.     

The soapberry bug,Jadera haematoloma (Insecta,Hemiptera, Rhopalidae): First Asian record,with?a?review of bionomics

The soapberry bug, Jadera haematoloma (Herrich-Schäffer, 1847) (Insecta: Hemiptera: Heteroptera: Rhopalidae: Serinethinae), a species native in tropical and subtropical regions of the New World and accidentally introduced to Hawaii, is reported for the first time from Asia (Taiwan). This record represents the first occurrence of the species in Asia. Stable populations composed of hundreds of specimens were found in seven localities of Kaohsiung City and one locality in Tainan City, and a single specimen was observed in Chiayi County. Aggregating adults and larvae fed in large numbers on the sapindacean plants Cardiospermum halicacabum L. and Koelreuteria elegans (Seem.) A. C. Smith ssp. formosana (Hayata) F. G. Meyer. Diagnostic characters of adults and larvae of Jadera haematoloma are discussed. A review of its bionomics and a bibliography are provided. Initial observations on the populations in southern Taiwan are presented. The species is potentially invasive, and further extension of its range is anticipated in Southeast Asia.     

Genetic differentiation among sympatric cuckoo host races: males matter

Generalist parasites regularly evolve host-specific races that each specialize on one particular host species. Many host-specific races originate from geographically structured populations where local adaptations to different host species drive the differentiation of distinct races. However, in sympatric populations where several host races coexist, gene flow could potentially disrupt such host-specific adaptations. Here, we analyse genetic differentiation among three sympatrically breeding host races of the brood-parasitic common cuckoo, Cuculus canorus. In this species, host-specific adaptations are assumed to be controlled by females only, possibly via the female-specific W-chromosome, thereby avoiding that gene flow via males disrupts local adaptations. Although males were more likely to have offspring in two different host species (43% versus 7%), they did not have significantly more descendants being raised outside their putative foster species than females (9% versus 2%). We found significant genetic differentiation for both biparentally inherited microsatellite DNA markers and maternally inherited mitochondrial DNA markers. To our knowledge, this is the first study that finds significant genetic differentiation in biparentally inherited markers among cuckoo host-specific races. Our results imply that males also may contribute to the evolution and maintenance of the different races, and hence that the genes responsible for egg phenotype may be found on autosomal chromosomes rather than the female-specific W-chromosome as previously assumed.     

Rapidly evolving adaptations to host ecology and nutrition in the soapberry bug

With reciprocal rearing experiments, we tested the hypothesis that adaptive differences in host-use traits among soapberry bug populations have a genetic basis. These experiments were conducted with two host races from Florida, an ancestral-type one on a native host plant species and a derived one on a recently introduced plant species (colonized mainly post-1950), on whose seed crops this insect depends for growth and reproduction. Compared to the native host species, the introduced host produces larger seed crops over a much briefer annual period. Its seeds are also significantly higher in lipids and lower in nitrogen. The bug populations exhibit greater juvenile survivorship on their home hosts; that is, the derived population survives better on seeds of the introduced host than does its ancestral-type counterpart, and vice versa. Regardless of the rearing host, populations from the introduced host lay much smaller eggs, and fecundity measures show a more complex pattern than does survivorship: the ancestral-type population produces eggs at the same rate on each host, while the derived population is less fecund on the native host and exhibits enhanced fecundity on the introduced host. These results indicate that the population differences are evolved rather than host-induced. They appear to be adaptive responses to host differences in the spatial and temporal distribution of seed availability and nutritional quality, and show that increased performance on the alien host has evolved with surprising speed and magnitude, with concomitant reductions in performance on the original host.     

The pace of modern life II: from rates of contemporary microevolution to pattern and process

We compiled a database of microevolution on contemporary time scales in nature (47 source articles; 30 animal species), comprising 2649 evolutionary rates in darwins (proportional change per million years) and 2151 evolutionary rates in haldanes (standard deviations per generation). Here we demonstrate how quantitative rate measures can provide general insights into patterns and processes of evolution. The frequency distribution of evolutionary rates was approximately log-normal, with many slow rates and few fast rates. Net selection intensities estimated from haldanes were on average lower than selection intensities commonly measured directly in natural populations. This difference suggests that natural selection could easily accomplish observed microevolution but that the intensities of selection typically measured in nature are rarely maintained for long (otherwise observed evolutionary rates would be higher). Traits closely associated with fitness (life history traits) appear to evolve at least as fast as traits less closely tied to fitness (morphology). The magnitude of evolutionary difference increased with the length of the time interval, particularly when maximum rates from a given study were considered. This pattern suggests a general underlying tendency toward increasing evolutionary diversification with time. However, evolutionary rates also tended to decrease with time, perhaps because longer time intervals average increasingly disparate rates over time, or because evolution slows when populations approach new optima or as genetic variation is depleted. In combination, our results suggest that macroevolutionary transitions may ultimately arise through microevolution occasionally writ large but are perhaps temporally characterized by microevolution writ in fits and starts.     

The adaptive significance of mate guarding in the soapberry bug,Jadera Haematoloma (Hemiptera: Rhopalidae)

Male soapberry bugs (Jadera haematoloma)face severe mating competition at the northern edge of their range due to male-biased adult sex ratios. Copulations lasting up to 11 days may serve a mate guarding function (encompassing four or more ovipositions), but copulation duration is highly variable, with some pairings lasting as little as 10 min. Data were gathered to describe factors that influence the reproductive costs and benefits of prolonged copulation. Estimated copulation durations (mean ± SD) were 20 ± 23 h in the lab and 50 ± 8 h in the field and were only weakly affected by sex ratio. Females mated for 5 min produced as many fertile eggs as those mated for 600 min laid; they became depleted of fertile sperm after about 25 days. In twicemated females, the first male's paternity was reduced by about 60%, and all females (N = 13) whose mates were removed experimentally mated again within an average of 6 min. The outcome of sperm competition on a perclutch basis was not highly predictable. The possibility of increased sperm displacement in longer copulations was not tested. Males often guarded females during oviposition and successfully defended them from intruding single males by recopulating. Such intrusions occurred in the majority of oviposition attempts observed in nature. Even though most females mated promiscuously, in a focal aggregation with a mean sex ratio of 2.2 ± 0.4 males/female, the interval between matings by males was commonly several days. Males appeared to respond facultatively to several aspects of the distribution and availability of females. The intensities of mating competition and sperm competition indicate that monogamous mate guarding should be favored over nonguarding in nature. Unpredicted brief. pairings may result from assessment by males of female reproductive value or of their own physical condition, or from female resistance.     

Genetic differentiation between two host “races” and two species of cleptoparasitic bees and between their two hosts

In this paper we test the following two hypotheses: (1) that apparently conspecific samples of the cleptoparasitic beeCoelioxys funeraria, differing markedly in size and reared from different host species, do indeed represent one panmictic population; (2) that bees that nest in holes in wood or twigs have higher levels of genetic variation than those nesting in the ground. Based upon 41 loci, the genetic differences between the two samples ofC. funeraria could be explained entirely in terms of sampling error. In contrast, the sympatricC. moesta showed 16 fixed allelic differences from theC. funeraria samples. Similarly, the two hosts ofC. funeraria, Megachile relativa andM. inermis, had 21 fixed allelic differences between them out of 42 presumptive gene loci. Heterozygosities among the wood-nesting bees were not particularly high for Hymenoptera, ranging from 0.045 to 0.054. Comparisons of heterozygosity estimates among bees remain ambiguous as to whether soil nesting confers sufficient environmental buffering effects to reduce possible advantages of heterosis in ground-nesting species.     

Beyond the phenotypic gambit: molecular behavioural ecology and the evolution of genetic architecture

Most studies of behaviour examine traits whose proximate causes include sensory input and neural decision-making, but conflict and collaboration in biological systems began long before brains or sensory systems evolved. Many behaviours result from non-neural mechanisms such as direct physical contact between recognition proteins or modifications of development that coincide with altered behaviour. These simple molecular mechanisms form the basis of important biological functions and can enact organismal interactions that are as subtle, strategic and interesting as any. The genetic changes that underlie divergent molecular behaviours are often targets of selection, indicating that their functional variation has important fitness consequences. These behaviours evolve by discrete units of quantifiable phenotypic effect (amino acid and regulatory mutations, often by successive mutations of the same gene), so the role of selection in shaping evolutionary change can be evaluated on the scale at which heritable phenotypic variation originates. We describe experimental strategies for finding genes that underlie biochemical and developmental alterations of behaviour, survey the existing literature highlighting cases where the simplicity of molecular behaviours has allowed insight to the evolutionary process and discuss the utility of a genetic knowledge of the sources and spectrum of phenotypic variation for a deeper understanding of how genetic and phenotypic architectures evolve.     

Genetic architecture and adaptive significance of the selfing syndrome in Capsella

The transition from outcrossing to predominant self-fertilization is one of the most common evolutionary transitions in flowering plants. This shift is often accompanied by a suite of changes in floral and reproductive characters termed the selfing syndrome. Here, we characterize the genetic architecture and evolutionary forces underlying evolution of the selfing syndrome in Capsella rubella following its recent divergence from the outcrossing ancestor C. grandiflora. We conduct genotyping by multiplexed shotgun sequencing and map floral and reproductive traits in a large (N= 550) F2 population. Our results suggest that in contrast to previous studies of the selfing syndrome, changes at a few loci, some with major effects, have shaped the evolution of the selfing syndrome in Capsella. The directionality of QTL effects, as well as population genetic patterns of polymorphism and divergence at 318 loci, is consistent with a history of directional selection on the selfing syndrome. Our study is an important step toward characterizing the genetic basis and evolutionary forces underlying the evolution of the selfing syndrome in a genetically accessible model system.     

基于微卫星标记的桃蚜种群寄主遗传分化

桃蚜Myzus persicae(Sulzer)是寄主范围最广、危害最大的蚜虫种类之一。为了探明桃蚜在不同寄主上的遗传分化特点,采用微卫星分子标记技术,对西兰花、桃树、辣椒上的桃蚜种群进行遗传多样性和遗传结构研究。结果表明,在所选用的5个微卫星位点上共检测到38个等位基因,平均每个位点的等位基因数达到7.6个,桃树种群遗传多样性最高,这可能是因为各种夏寄主上的桃蚜迁回桃树上越冬,从而使多种等位基因和基因型得以聚集的原因。等位基因频率差异分析显示西兰花种群、桃树种群和辣椒种群两两之间(除了桃树06种群和辣椒06种群之间没有遗传分化外)都出现了明显遗传分化,相比之下桃树种群和辣椒种群的分化程度要比桃树种群和西兰花种群的分化程度低,这可能预示着西兰花寄主上的桃蚜正在向远离桃树和辣椒种群的方向进化。     

Ethanol resistance in Drosophila melanogaster has increased in parallel cold‐adapted populations and shows a variable genetic architecture within and between populations

Understanding the genetic properties of adaptive trait evolution is a fundamental crux of biological inquiry that links molecular processes to biological diversity. Important uncertainties persist regarding the genetic predictability of adaptive trait change, the role of standing variation, and whether adaptation tends to result in the fixation of favored variants. Here, we use the recurrent evolution of enhanced ethanol resistance in Drosophila melanogaster during this species’ worldwide expansion as a promising system to add to our understanding of the genetics of adaptation. We find that elevated ethanol resistance has evolved at least three times in different cooler regions of the species’ modern range—not only at high latitude but also in two African high‐altitude regions. Applying a bulk segregant mapping framework, we find that the genetic architecture of ethanol resistance evolution differs substantially not only between our three resistant populations, but also between two crosses involving the same European population. We then apply population genetic scans for local adaptation within our quantitative trait locus regions, and we find potential contributions of genes with annotated roles in spindle localization, membrane composition, sterol and alcohol metabolism, and other processes. We also apply simulation‐based analyses that confirm the variable genetic basis of ethanol resistance and hint at a moderately polygenic architecture. However, these simulations indicate that larger‐scale studies will be needed to more clearly quantify the genetic architecture of adaptive evolution and to firmly connect trait evolution to specific causative loci.     

High genetic diversity and population differentiation in Boechera fecunda, a rare relative of Arabidopsis

Conservation of endangered species becomes a critical issue with the increasing rates of extinction. In this study, we use 13 microsatellite loci and 27 single-copy nuclear loci to investigate the population genetics of Boechera fecunda, a rare relative of Arabidopsis thaliana, known from only 21 populations in Montana. We investigated levels of genetic diversity and population structure in comparison to its widespread congener, Boechera stricta, which shares similar life history and mating system. Despite its rarity, B. fecunda had levels of genetic diversity similar to B. stricta for both microsatellites and nucleotide polymorphism. Populations of B. fecunda are highly differentiated, with a majority of genetic diversity existing among populations (F(ST) = 0.57). Differences in molecular diversity and allele frequencies between western and eastern population groups suggest they experienced very different evolutionary histories.     

Genetic variability and differentiation of hypogean Cyprinid fishes from Somalia

The genetic structure of populations of two hypogean Somali cyprinid species was compared by analysing genetic variation at 30 allozyme loci. The two species, Phreatichthys andruzzii and Barbopsis devecchii , are of particular interest, representing two different steps in adaptation to cave life, as indicated by several morphological features including eye regression. Phreatichthys is completely anophthalmic, while Barbopsis shows a highly variable microphthalmia. Results showed a close relationship between Phreatichthys and Barbopsis , suggesting their origin from a common epigean ancestor. Population structure of the two species differs and levels of gene flow are much higher between the Barbopsis populations than between the Phreatichthys populations. Two possible scenarios leading to the current situation are hypothesized.     

Trends and rates of microevolution in plants

Evidence for rapid evolutionary change in plants in response to changing environmental conditions is widespread in the literature. However, evolutionary change in plant populations has not been quantified using a rate metric that allows for comparisons between and within studies. One objective of this paper is to estimate rates of evolution using data from previously published studies to begin a foundation for comparison and to examine trends and rates of microevolution in plants. We use data gathered from studies of plant adaptations in response to heavy metals, herbicide, pathogens, changes in pH, global change, and novel environments. Rates of evolution are estimated in the form of two metrics, darwins and haldanes. A second objective is to demonstrate how estimated rates could be used to address specific microevolutionary questions. For example, we examine how evolutionary rate changes with time, life history correlates of evolutionary rates, and whether some types of traits evolve faster than others. We also approach the question of how rates can be used to predict patterns of evolution under novel selection pressures using two contemporary examples: introductions of non-native species to alien environments and global change.     

Partitioning adaptive differentiation across a patchy landscape: shade avoidance traits in impatiens capensis

Adaptation to different habitat types across a patchy landscape may either arise independently in each patch or occur due to repeated colonization of each patch by the same specialized genotype. We tested whether open- and closed-canopy forms of Impatiens capensis, an herbaceous annual plant of eastern North America, have evolved repeatedly by comparing hierarchical measures of F(ST) estimated from AFLPs to morphological differentiation measured by Q(ST) for five pairs of populations found in open and closed habitats in five New England regions. Morphological differentiation between habitats (Q(HT)) in elongation traits was greater than marker divergence (F(HT)), suggesting adaptive differentiation. Genotypes from open- and closed-canopy habitats differed in shade avoidance traits in several population pairs, whereas patterns of AFLP differentiation suggest this differentiation does not have a single origin. These results suggest that open- and closed-canopy habitats present different selective pressures, but that the outcome of diversifying selection may differ depending on specific closed- and open-canopy habitats and on starting genetic variation. Hierarchical partitioning of F(ST) and Q(ST) makes it possible to distinguish global stabilizing selection on traits across a landscape from diversifying selection between habitat types within regions.     

北京西海萼花臂尾轮虫（Brachionus calyciflorus）种群休眠卵库的遗传分化

利用线粒体细胞色素氧化酶Ⅰ亚基(COI)序列片段(543bp)对孵化自西海萼花臂尾轮虫休眠卵库的46个克隆进行分析,共发现6个单倍型,平均遗传距离为0.032,分别聚在2个分支.选取4个出现频率较高的克隆群,分别对其在3种食物浓度(蛋白核小球藻Chlorella pyrenoidosa,1×106 cells/ml,6×106 cells/ml,12×106 cells/ml)和3种温度(15℃,25℃,35℃;蛋白核小球藻Chlorella pyrenoidosa,6×106 cells/ml)下的适合度特征(R0和rm)以及个体大小(背甲长和背甲宽)进行比较研究.生命表实验结果显示,单倍型与食物浓度的交互作用(R0:P=0.038;rm:P=0.027)以及单倍型与温度的交互作用(R0:P=0.006;rm:P=0.000)对种群增长均有显著影响,这4个单倍型克隆群对环境条件具有不同的偏好,并且各个克隆群对于环境变化有不同的生殖反应.形态测量结果显示,单倍型与温度的交互作用(背甲长:P=0.033;背甲宽:P=0.000)以及单倍型与温度的交互作用(背甲长:P=0.027;背甲宽:P=0.000)对个体大小均有明显的影响.结合生命表及形态数据,探讨了休眠卵库中各个克隆群的生态位及形态分化以及可能对种群结构的动态变化产生的影响.     

暗褐蝈螽不同地理种群间的遗传分化

利用线粒体COI基因片段研究了我国吉林、辽宁、内蒙古、河北和四川的暗褐蝈螽(Gampsocleis sedakovii)12个地理种群间的遗传分化。结果表明: 36条626 bp的mtDNA-COI基因片段中共检测到单倍型29种, 多态位点71个, 其中简约信号位点37个, 单一多态位点34个。分子变异等级分析(AMOVA)的计算结果显示, 群体内变异仅占总变异的37.23%, 明显小于群体间变异, Fst值为0.62770, 各群体间呈现明显的遗传分化。最大简约法(MP)系统发育分析结果显示, 暗褐蝈螽的12个地理种群以极高的自举支持度(100%)聚类, 形成两个独立的分枝。由于两个分枝的聚类结果与基于形态学特征划分的两个亚种(Gampsocleis sedakovii sedakovii和Gampsocleis sedakovii obscura)并不对应。综合采集地的生境, 初步推测暗褐蝈螽两个亚种间的形态学差异可能是由于它们所处生境不同所引起。在12个地理种群中, 只有内蒙古通辽(NTL)的个体在两个分枝中均有出现。单倍型分布格局研究发现, 单倍型H10是内蒙古通辽(NTL)、鄂温克(NEWK)和吉林吉林(JJL)3个地理种群的共享单倍型, 说明它们来自于共同的祖先。研究结果支持我国的东北地区是暗褐蝈螽遗传分化中心的观点, 但不支持基于形态学特征划分的两个亚种。