THE GENETICS OF GENDER AND THE EFFECTS OF GENDER ON FLORAL CHARACTERS IN GYNODIOECIOUS PHACELIA LINEARIS (HYDROPHYLLACEAE)

The evolution of gynodioecy depends in part on the location (nucleus or cytoplasm) of gender-determining genes. Characters genetically correlated with gender also can be important in the evolution of this sexual system. For example, gender differences in the costs of flowers affect the potential for resource compensation by females for the loss of male function. This paper reports the genetics of gender and the nature of secondary sex characters of flowers in Phacelia linearis (Hydrophyllaceae), a gynodioecious annual in which females exhibit substantial compensation. A single nuclear gene has a major effect on gender, recessive homozygotes being male-sterile, but not all the data can be explained by this or other simple inheritance models. In nature, hermaphrodites have wider corollas than females and begin to flower slightly later than females. In a common environment, gender effects on corolla size are modified by genetic background and/or maternal effects. Hermaphrodite flowers have 15% greater dry biomass than female flowers, but similar ovule number and nectar sugar production. Hermaphrodite and female flowers differ in the linear dimensions and biomass allocation of several floral organs. In particular, the androecia and corollas of female flowers are smaller than those of hermaphrodite flowers, both in absolute terms and relative to the size of the rest of the flower. Corolla size reduction could be an important source of resources for compensation by females.     

POLLINATION AND SEED PRODUCTION IN IPOMOPSIS AGGREGATA: DIFFERENCES AMONG AND WITHIN FLOWER COLOR MORPHS

The pollination of red, pink, and white color morphs of Ipomopsis aggregata was evaluated to assess whether ethological isolation based on pollinator color discrimination may occur. We observed animal visitors, assessed pollen delivery, seed set per fruit, percentage of flowers setting fruit, nectar production, and timing of flower opening for different color morphs in the Front Range of Colorado. Based on traditional zoophilous flower classifications, we expected hummingbirds to pollinate red-flowered I. aggregata subsp. collina and hawkmoths to pollinate white-flowered I. aggregata subsp. Candida. However, ethological isolation does not appear to occur among color morphs of I. aggregata in the Front Range. Hummingbirds visited red-flowered plants in excess overall, and, to a lesser extent, so did hawkmoths. Both hummingbirds and hawkmoths visited all color morphs and probably transferred pollen among them. Pollen delivery data and a day-night bagging experiment also suggest that pollinators do not necessarily behave as predicted by flower classifications. In addition, there is little evidence for major differences between red, white, and pink flowers in any aspects of reproductive biology. Indeed, most variation occurs within a given color morph.     

INBREEDING DEPRESSION IN GYNODIOECIOUS LOBELIA SIPHILITICA: AMONG-FAMILY DIFFERENCES OVERRIDE BETWEEN-MORPH DIFFERENCES

If inbreeding depression is caused by deleterious recessive alleles, as suggested by the partial dominance hypothesis, a negative correlation between inbreeding and inbreeding depression is predicted. This hypothesis has been tested several times by comparisons of closely related species or comparisons of populations of the same species with different histories of inbreeding. However, if one is interested in whether this relationship contributes to mating-system evolution, which occurs within populations, comparisons among families within a population are needed; that is, inbreeding depression among individuals with genetically based differences in their rate of selfing should be compared. In gynodioecious species with self-compatible hermaphrodites, hermaphrodites will have a greater history of potential inbreeding via both selfing and biparental inbreeding as compared to females and may therefore express a lower level of inbreeding depression. We estimated the inbreeding depression of female and hermaphrodite lineages in gynodioecious Lobelia siphilitica in a greenhouse experiment by comparing the performance of selfed and outcrossed progeny, as well as sibling crosses and crosses among subpopulations. We did not find support for lower inbreeding depression in hermaphrodite lineages. Multiplicative inbreeding depression (based on seed germination, juvenile survival, survival to flowering, and flower production in the first growing season) was not significantly different between hermaphrodite lineages (δ = 0.30 ± 0.08) and female lineages (δ = 0.15 ± 0.18), although the trend was for higher inbreeding depression in the hermaphrodite lineages. The population-level estimate of inbreeding depression was relatively low for a gynodioecious species (δ = 0.25) and there was no significant inbreeding depression following biparental inbreeding (δ = 0.01). All measured traits showed significant variation among families, and there was a significant interaction between family and pollination treatment for four traits (germination date, date of first flowering, number of flowers, and aboveground biomass). Our results suggest that the families responded differently to selfing and outcrossing: Some families exhibited lower fitness following selfing whereas others seemed to benefit from selfing as compared to outcrossing. Our results support recent simulation results in that prior inbreeding of the lineages did not determine the level of inbreeding depression. These results also emphasize the importance of determining family-level estimates of inbreeding depression, relative to population-level estimates, for studies of mating-system evolution.     

克隆植物的无性与有性繁殖对策

许多植物同时具有克隆生长与有性繁殖,两种繁殖方式间的平衡在不同物种间以及同一物种内不同种群间变化很大。旺盛的克隆生长可能会从多方面影响生活史进化。首先,许多克隆植物的有性繁殖与更新程度都很低,甚至有一些植物由于克隆生长而几乎完全放弃了有性过程,从而影响到克隆植物对局域环境的适应和地理范围进化。其次,克隆生长增大花展示进而增加了对传粉者的吸引,同时也增加了同株异花授粉的风险,而同株异花授粉往往会导致植物雄性和雌性适合度的下降。因此,克隆植物的空间结构与交配方式间可能存在着协同进化关系。最后,克隆生长与有性繁殖间可能存在着权衡关系:对克隆生长的资源投入将会减少对有性繁殖的资源投入。这种权衡关系可能是由环境条件、竞争力度、植物寿命和遗传等因素决定的。如果不同的繁殖方式是植物在不同环境下采取的适应性对策,那么我们可以预期:在波动和竞争力度大的生境中,植物应将大部分的繁殖资源分配给有性繁殖;而在相对稳定的环境中,克隆繁殖应该占据优势地位。但是自然选择对两种繁殖方式的选择结果是什么,以及控制这两种方式间平衡的生态和遗传因子究竟有哪些,到底是克隆生长单向地影响了植物的有性繁殖,还是与有性过程相伴随的选择压力同时塑造了植物的克隆习性?目前尚不清楚。同时从无性与有性繁殖两个方面综合考察克隆植物的繁殖对策是今后亟待加强的工作。     

东北草原羊草种群种子生产与气候波动的关系

羊草（Leymus chinensis(Trin.)Tzvel.）是一种优良的多年生禾本科牧草。东北草原羊草种群种子生产有明显的丰欠年现象。通过对3个固定样地连续12－16年的调查和测定及其与不同生长发育阶段光照时间、积温、降水量的相关分析,发现气候变化是引起羊草种群种子生产丰欠年的重要因素之一。秋季低温、多雨,翌年将是种子生产的丰年,而高温、干旱则是欠年。相反,春季高温、干旱是种子生产的丰年,而低温、多雨则是欠年。气候因子对羊草种群种子生产有明显滞后的生态效应,其影响的生态时间差可长达10－12个月之久。用前一年8－10月不同阶段的降水可预报翌年羊草种群的抽穗数量和籽实产量,但由单项降水因子引起的诸数量变化为44％－61％。     

VARIATION IN MALE REPRODUCTIVE INVESTMENT AND MALE REPRODUCTIVE SUCCESS IN WHITE SPRUCE

An experimental population composed of ramets of white spruce clones was studied to determine the influence of different levels of clonal male reproductive investment on clonal male reproductive success, where the male reproductive success of different clones in the population was defined as the proportion of the seed crop sired by each clone. We present a multilocus estimation procedure which provides unbiased estimates of the proportion of seed sired by each parental genotypic class from pollen gamete frequency data, whenever gametic segregation frequencies are known. Significant linear and quadratic components were found for the relationship between the number of male cones produced and the estimated proportion of the seed crop sired. A clone that produced an exceptionally large number of male cones, however, did not have the greatest male reproductive success. In general, the results support an assumption made in theoretical models of selection on mating system modifiers regarding the relationship between male investment and male reproductive success. They also support the hypothesis that male reproductive success in wind-pollinated species continues to increase substantially with increasing male reproductive investment.     

POPULATION VARIATION AND HYBRIDIZATION IN SEA-ROCKETS (CAKILE,CRUCIFERAE): SEED GLUCOSINOLATE CHARACTERS

In a study of intra- and interpopulation variation in seed glucosinolates, remarkable uniformity was found among individuals within the two chemically distinct subspecies of East Coast Cakile edentula. Glucosinolates were used as taxonomic markers in a study of hybridization between ssp. edentula and ssp. harperi where they form mixed populations on the Outer Banks of North Carolina. Thirteen plants with hybrid chemical profiles were detected in a sample of 89 individuals from four populations; the zone of hybridization is narrow, and has persisted for at least eight years. Artificial hybrids of the two subspecies are additive for kinds and intermediate for proportions of seed glucosinolates, and families of F₂'s show a range of recombinant chemical profiles. Natural hybridization was confirmed by recovering hybrid and parental types in 47 progeny of three presumptive wild hybrids. Glucosinolate profile characteristics segregated independently of the segregation patterns for fruit length and seed weight. Selection against particular glucosinolate phenotypes is one possible mechanism maintaining this narrow hybrid zone on the Outer Banks.     

REPRODUCTIVE CAPACITY AND SEED SIZE IN LUPINUS TEXENSIS

The average number of ovules produced per individual of Lupinus texensis is much greater than the average number of seeds per plant. Each plant produces approximately 2,000 ovules but only 2.5% develop into seeds. One fourth of the seeds is lost due to abortion and 0.3% is lost due to predation on the plant. Mature seeds from this population exhibit a five-fold range in weight, from 10 to 56 mg. The distribution of seed weights in the field population is skewed and leptokurtic. Seed wt is positively correlated with both seed germination and seedling survivorship. Heritability of seed wt is 0.09. There is no correlation between average seed wt per plant and total number of seeds per plant, seeds per pod, or legumes per plant.     

INTRASEASONAL VARIATION IN SEED PRODUCTION AMONG FLOWERS AND PLANTS OF THALICTRUM THALICTROIDES (RANUNCULACEAE)

Intraseasonal variation in ovule and seed production per flower and per plant of the perennial herb Thalictrum thalictroides (L.) Eames and Boivin was documented at three sites during three spring flowering seasons. Shading and pollen-addition experiments were used to assess the impact of variation in pollination and light availability on seed production. Mean seed number and percent seed set were lower in flowers open late in the season than in those open earlier. The lower percent seed set occurs primarily in flowers that are positioned laterally on the inflorescence and which open later than center flowers. Plants flowering early in the season produce more flowers, ovules and seeds than those flowering later. Mean percent seed set per plant did not change, however, indicating that temporal differences in total seed output can be traced largely to variation in total ovule number. Seed production may be limited by lack of pollination during periods of inclement weather. At least late in the season, seed output may also be resource-limited: the decline in percent seed set among flowers coincided with the decline in light availability, and hand-pollination of late-opening flowers did not increase percent seed set to earlier levels. Artificial shading led to a significant reduction in percent seed set of lateral flowers, and decreased the probability of flowering again the following year. Thus, the relative selective roles of resource and pollination limitations may vary during the flowering season.     

GENDER DIFFERENCES IN DIURNAL VARIATIONS OF SUBJECTIVE ACTIVATION AND MOOD

This article evaluates the influence of gender on diurnal and postlunch period variations in subjective activation and mood. This topic is not often addressed in the literature; particularly, little attention has been paid to how biological rhythms might bias research results. We studied 40 university student volunteers (20 men, 20 women) aged 18 to 23 years old (X = 20.23, SD = 1.03); they responded to questions on eight unipolar visual analog scales every hour from 08:00 to 21:00. Gender differences were observed in both diurnal and postlunch variations for scales of positive activation (alertness, vigor); sleepiness, however, was only sensitive to diurnal variation, and weariness was sensitive only to a postlunch effect. Women displayed a morning- type pattern, with their optimal moment (11:00) coming 2h earlier than for men, and their activation ratings ranged more widely. The only mood scale that showed differences related to gender was that of happiness, for which women had a higher diurnal mean, a diurnal peak 2h earlier, and a less-intense postlunch effect. Endogenous control of rhythmic pattern appears to be less intense in women, probably due to the coexistence of circamensual rhythmicity, although environmental or sociocultural influences may play a modulating role. Chronopsychological gender differences in affective states should be studied further given the implication they have for the prevention and treatment of mood disorders. (Chronobiology International, 18(3), 491–502, 2001)     

INFLORESCENCE CHARACTERS AND REPRODUCTIVE PROFICIENCY IN DANTHONIA SERICEA POPULATIONS

The purpose of this research was the comparison of inflorescence and fruiting characters of populations of Danthonia sericea in relation to both latitude and habitat. Mature panicles were collected in 1969 and 1970 from six New Jersey (three well drained and three bog) and four Georgia (two in well-drained sites and two in seepage areas adjacent to granite outcrops) populations. Data analyses showed significant differences between population groupings based on latitude (New Jersey vs. Georgia) and habitat (well drained vs. wet). Populations from the wetter sites had significantly longer lemmas; populations from the well-drained sites had a significantly greater number of spikelets per panicle. Number of spikelets per panicle in Georgia populations significantly exceeded that of New Jersey populations, while caryopses in the New Jersey populations were significantly heavier. In both New Jersey and Georgia, populations from the relatively drier sites had significantly heavier caryopses and a greater percentage of florets with caryopses. Since the well-drained group and the Georgia group both had a greater number of florets and a greater percentage of florets with caryopses, these two groups were shown to have the greatest reproductive proficiency. Possible adaptive significance of differences in number of seed produced and in seed weight is discussed.     

POPULATION SEX STRUCTURE AND REPRODUCTIVE FITNESS IN GYNODIOECIOUS SIDALCEA MALVIFLORA MALVIFLORA (MALVACEAE)

The spatial distribution of females and hermaphrodites within gynodioecious populations is expected to exert considerable selective pressure on gender fitness through pollen limitation of seed set. If pollen flow is predominantly local, seed set in individual plants may be sensitive to the proximity of pollen donors; pollen limitation of seed set may occur if hermaphrodites are locally rare. Under such circumstances, female fitness will be negatively frequency dependent and hermaphrodite fitness will be positively frequency dependent. Given local seed dispersal, a nonrandom clumped distribution of the genders is expected in gynodioecious populations due to the heritability of gender in gynodioecious species. If gender fitness is frequency dependent, such structure should favor hermaphrodites and select against females. To test this hypothesis, I quantified the distribution of the genders in terms of nearest neighbors and neighborhood sex ratio in two populations of gynodioecious Sidalcea malviflora malviflora. I then measured the effect of neighborhood sex ratio on open-pollinated seed set and pollen limitation in both manipulated and unmanipulated neighborhoods. Results indicate that the genders have a patchy distribution and that both genders are pollen limited and show an increase in seed set with an increase in neighborhood hermaphrodite frequency. The observed population sex structure favors hermaphrodites and disadvantages females. These results highlight the importance that population-level traits can have in determining individual fitness and the evolution of sex ratios in gynodioecious species.     

SEED SIZE AND SEED PACKAGING VARIATION IN BAPTISIA LANCEOLATA (FABACEAE)

Pods and seeds of field-collected Baptisia lanceolala plants were analyzed to partition seed weight and seed packaging trait variance among and within plants and to detect relationships between these traits. Packaging traits studied were: pod weight, seed weight per pod, number of seeds per pod, mean weight of seeds per pod, proportion seed weight of total pod weight, and pod weight per seed. Significant among-plant variation was found for seed weight and all packaging traits. Within plants, positive correlations were found between number of seeds per pod and pod dry weight and between the proportion seed weight of total pod weight and number of seeds per pod. Pod weight per seed was negatively correlated with number of seeds per pod. Most plants had a negative correlation between mean seed weight and number of seeds per pod. When compared with an equality of slopes test, slopes of regressions of the above pairs of traits were found to differ among plants. Among plants, the same relationships were found, except for the latter two traits, which were not correlated. These within-plant patterns may represent constraints on seed weight variance imposed by the seed package. This view is supported by a positive correlation between packaging trait variance and seed weight variance. Packaging-related constraints could have an effect on seed weight in this and other species. If these phenotypic constraints have a genetic basis, then selection on seed packaging could change seed weight in a way different from that which might be predicted by considering seed weight alone.     

GEOGRAPHIC DIFFERENCES IN SEXUAL REASSORTMENT IN RNA PHAGE

The genetic structure of natural bacteriophage populations is poorly understood. Recent metagenomic studies suggest that phage biogeography is characterized by frequent migration. Using virus samples mostly isolated in Southern California, we recently showed that very little population structure exists in segmented RNA phage of the Cystoviridae family due to frequent segment reassortment (sexual genetic mixis) between unrelated virus individuals. Here we use a larger genetic dataset to examine the structure of Cystoviridae phage isolated from three geographic locations in Southern New England. We document extensive natural variation in the physical sizes of RNA genome segments for these viruses. In addition, consistent with earlier findings, our phylogenetic analyses and calculations of linkage disequilibrium (LD) show no evidence of within‐segment recombination in wild populations. However, in contrast to the prior study, our analysis finds that reassortment of segments between individual phage plays a lesser role among cystoviruses sampled in New England, suggesting that the evolutionary importance of genetic mixis in Cystoviridae phage may vary according to geography. We discuss possible explanations for these conflicting results across the studies, such as differing local ecology and its impact on phage growth, and geographic differences in selection against hybrid phage genotypes.     

VARIATION IN SEED CHARACTERS IN NEMOPHILA MENZIESII: EVIDENCE OF A GENETIC BASIS FOR MATERNAL EFFECT

A growing body of evidence indicates that phenotypic selection on juvenile traits of both plants and animals may be considerable. Because juvenile traits are typically subject to maternal effects and often have low heritabilities, adaptive responses to natural selection on these traits may seem unlikely. To determine the potential for evolutionary response to selection on juvenile traits of Nemophila menziesii (Hydrophyllaceae), we conducted two quantitative genetic studies. A reciprocal factorial cross, involving 16 parents and 1960 progeny, demonstrated a significant maternal component of variance in seed mass and additive genetic component of variance in germination time. This experiment also suggested that interaction between parents, though small, provides highly significant contributions to the variance of both traits. Such a parental interaction could arise by diverse mechanisms, including dependence of nuclear gene expression on cytoplasmic genotype, but the design of this experiment could not distinguish this from other possible causes, such as effects on progeny phenotype of interaction between the environmental conditions of both parents. The second experiment, spanning three generations with over 11,000 observations, was designed for investigation of the additive genetic variance in maternal effect, assessment of paternal effects, as well as further partitioning of the parental interaction identified in the reciprocal factorial experiment. It yielded no consistent evidence of paternal effects on seed mass, nor of parental interactions. Our inference of such interaction effects from the first experiment was evidently an artifact of failing to account for the substantial variance among fruits within crosses. The maternal effect was found to have a large additive genetic component, accounting for at least 20% of the variation in individual seed mass. This result suggests that there is appreciable potential for response to selection on seed mass through evolution of the maternal effect. We discuss aspects that may nevertheless limit response to individual selection on seed mass, including trade-offs between the size of individual seeds and germination time and between the number of seeds a maternal plant can mature and their mean size.     

雅鲁藏布江黑斑原鮡繁殖生物学研究

对2004-2006年采集于雅鲁藏布江拉萨河的190尾黑斑原鮡进行了繁殖生物学研究。雄性最小性成熟(精巢Ⅳ期)个体体长141.7mm,体重45.2g,性体指数1.09%,雌性最小性成熟(卵巢Ⅳ期)个体体长146.8mm,体重66.7g性体指数11.52%,相应年龄均为5龄。初次性成熟年龄(L50):♂,170.1mm相应年龄为7龄;♀,150.2mm,相应年龄5龄。通过组织切片法和GSI的周年变化分析,繁殖时间集中在5-6月,每年繁殖一次,繁殖之后的6-8月卵巢从Ⅵ期回复到Ⅲ期,9月卵巢发育到Ⅳ期越冬。卵径频率分布显示,卵巢发育类型为分批同步型,卵巢中至少存在2批卵径,每年成熟一批卵并同时产出,产卵类型为完全同步产卵。卵黏性,成熟卵卵径在2.04-3.37mm之间,平均(2.83±0.16)mm。对19尾产卵前夕(体长为151.0-210.0mm)的标本进行统计,其绝对繁殖力范围在525-2058粒之间,平均为(1244±346)粒,相对繁殖力为(14.7±5.8)粒/g。绝对繁殖力与体长呈直线正相关,表达式为F=13.624L-1187。