日龄和交配状态对亚洲玉米螟雄蛾内生殖器特征的影响

【目的】揭示日龄和交配对亚洲玉米螟Ostrinia furnacalis雄蛾内生殖器官的影响,以及亚洲玉米螟雄蛾的交配状态和性信息素诱捕之间的关系。【方法】采用行为学和生殖器解剖技术,研究不同日龄和交配状态亚洲玉米螟雄蛾内生殖器特征,并将其与田间性信息素诱捕雄蛾进行比较。【结果】除了精巢、输精管、储精囊、附腺、复射精管和单射精管外,亚洲玉米螟雄蛾内生殖系统还包含1对附腺囊,同时单射精管非角质化区分为5段(PS1-5),PS1又细分为5区(PS1Ⅰ-Ⅴ)。生殖器内含物可分为5级(0-4级),存在充满和未充满生殖器两种状态。1日龄雄蛾内生殖系统不同器官的内含物等级存在差异,但是日龄对雄蛾生殖系统内含物等级无明显影响。交配后0 h亚洲玉米螟雄蛾,除输精管、储精囊和附腺囊外,其余生殖器官内含物等级较未交配雄蛾的均发生显著变化。随着交配后时间的增加,雄蛾生殖器内含物等级逐渐恢复,各器官内含物等级恢复的速度存在差异,交配后60 h所有内含物等级均恢复到未交配状态。但是直到交配后228 h,交配雄蛾PS5内含物仍然表现出断裂等形态特征,和未交配雄蛾存在差异。性信息素引诱雄蛾中有60.9%的生殖系统表...     

Homomorphic plant sex chromosomes are coming of age

Sex chromosomes are a very peculiar part of the genome that have evolved independently in many groups of animals and plants (Bull 1983 ). Major research efforts have so far been focused on large heteromorphic sex chromosomes in a few animal and plant species (Chibalina & Filatov 2011 ; Zhou & Bachtrog 2012 ; Bellott et al. 2014 ; Hough et al. 2014 ; Zhou et al. 2014 ), while homomorphic (cytologically indistinguishable) sex chromosomes have largely been neglected. However, this situation is starting to change. In this issue, Geraldes et al. ( 2015 ) describe a small (~100 kb long) sex‐determining region on the homomorphic sex chromosomes of poplars (Populus trichocarpa and related species, Fig.  1 ). All species in Populus and its sister genus Salix are dioecious, suggesting that dioecy and the sex chromosomes, if any, should be relatively old. Contrary to this expectation, Geraldes et al. ( 2015 ) demonstrate that the sex‐determining region in poplars is of very recent origin and probably evolved within the genus Populus only a few million years ago.     

Size advantage for male function and size‐dependent sex allocation in Ambrosia artemisiifolia,a wind‐pollinated plant

In wind‐pollinated plants, male‐biased sex allocation is often positively associated with plant size and height. However, effects of size (biomass or reproductive investment) and height were not separated in most previous studies. Here, using experimental populations of monoecious plants, Ambrosia altemisiifolia, we examined (1) how male and female reproductive investments (MRI and FRI) change with biomass and height, (2) how MRI and height affect male reproductive success (MRS) and pollen dispersal, and (3) how height affects seed production. Pollen dispersal kernel and selection gradients on MRS were estimated by 2,102 seeds using six microsatellite markers. First, MRI increased with height, but FRI did not, suggesting that sex allocation is more male‐biased with increasing plant height. On the other hand, both MRI and FRI increased with biomass but often more greatly for FRI, and consequently, sex allocation was often female‐biased with biomass. Second, MRS increased with both height and MRI, the latter having the same or larger effect on MRS. Estimated pollen dispersal kernel was fat‐tailed, with the maximum distance between mates tending to increase with MRI but not with height. Third, the number of seeds did not increase with height. Those findings showed that the male‐biased sex allocation in taller plants of A. artemisiifolia is explained by a direct effect of height on MRS.     

Evidence for effects of restorer genes on male and female reproductive functions of hermaphrodites in the gynodioecious species Thymus vulgaris L.

In Thymus vulgaris L., sex determination involves both the nuclear and the cytoplasmic genomes: the cytoplasm is responsible for male-sterility (the female phenotype) while specific nuclear genes may restore male fertility (the hermaphrodite phenotype). Previous observations have shown high variation among hermaphrodites for pollen and seed production. In order to investigate the origin of this variation, 12 female plants, four from each of three populations, were hand-pollinated with pollen from hermaphrodites from three different paternal populations. The sex-ratio (i.e. the frequency of hermaphrodites) produced and the reproductive functions of these offspring were measured. A strong positive correlation was observed between the sex-ratio within a family and both female and male reproductive functions of its hermaphrodites. No such correlation was found for females. This result suggests that restorer genes may be directly or indirectly involved both in sex determination and in the efficiency of resource allocation to reproductive functions. As a consequence, female advantage, i.e. the relative fecundity of females to hermaphrodites, is larger in families with low sex-ratio, and this might affect the evolution of this gynodioecious breeding system.     

Female access and diet affect insemination success,senescence and the cost of reproduction in the male Mexican fruit fly Anastrepha ludens

Hypotheses exploring the influence of dietary conditions on the life‐history trade‐off between survival and reproductive success are extensively tested in female insects but only rarely explored in males. The present study examines the impact of dietary quality and female access on age‐specific reproduction and survival of the male Mexican fruit fly Anastrepha ludens Loew (Diptera: Tephritidae). There is a clear cost of female access for males with access to dietary protein, measurable as a decrease in life expectancy, which is further influenced by the age when females are introduced. A protein deficient diet reduces the lifespan benefit of virginity and masks the detrimental effect of female access on male life expectancy. Dietary protein is not necessary for reproductive success, although access to protein at eclosion improves the lifetime reproductive success of males compared to when it is delayed. Overall, reproductive success diminishes as the male flies age, regardless of the dietary conditions, providing evidence for reproductive senescence in males. Delaying the males' access to a protein source fails to influence the negative effect of age on reproductive ability. Because age‐specific reproductive rates decline with age, regardless of diet, male fitness does not benefit from lifespan extension. Therefore, males can be expected to allocate available resources towards reproductive effort in favour of an extended lifespan, regardless of mate and protein availability.     

日龄和交配状态对二化螟雄蛾内生殖器特征的影响

【目的】性信息素群集诱杀应用于二化螟Chilo suppressalis测报和防治。本研究旨在明确性信息素群集诱杀二化螟的机理及诱集雄蛾的交配状态。【方法】利用行为学和生殖器解剖技术,研究不同日龄和交配状态二化螟雄蛾内生殖器特征,并将其与田间性信息素诱集获得的雄蛾进行比较。【结果】二化螟雄蛾单射精管非角质化区可分为7段;生殖器内含物主要为白色,紧实程度可以分为5级(0-4级),存在充满和未充满生殖器两种状态。随着日龄增加,雄蛾附腺以及第3和4段非角质化区内含物等级降低,第5和7段非角质化区内含物未充满比例升高,内含物为白色的比例下降。交配后1 h之内二化螟雄蛾第5和7段非角质化区和复射精管内含物等级显著低于未交配雄蛾,而第1-4段非角质化区内含物等级显著高于未交配雄蛾。交配后24 h,所有内含物等级和未交配雄蛾无显著差异;交配后36 h,第5和7段非角质化区内含物未充满比例高于未交配雄蛾。性信息素诱集和未诱集雄蛾生殖器内含物等级无显著差异。田间性信息素诱集雄蛾附腺端半部内含物等级显著高于2-6日龄未交配二化螟,第3和4段非角质化区内含物等级显著低于刚羽化(0日龄)雄蛾。【结论】本研究结果表明,利用生殖器内含物特征可以区别交配后12 h内的已交配和未交配二化螟雄蛾,性信息素群集诱杀的可能大部分是羽化1 d的未交配雄蛾。本研究结果为二化螟雄蛾交配状态判定和蛾类害虫性信息素测报和防治的有效性提供了一定依据。     

Anopheles culicifacies: effects of age on the male reproductive system and mating ability of virgin adult mosquitoes

Abstract. Under controlled laboratory conditions of 28–30^oC and 16:8 L:D photoperiod, an attempt was made to develop an age-grading technique for Anopheles culicifacies males. Mating activity was maximal when females were 5–12 days old and males were 5–7 days old. The numbers of total and mature spermatocysts declined significantly with age, and the proportion of the testes occupied by the sperm reservoir increased as virgin males grew older. Mating resulted in the loss of spermatozoa and accessory gland substance from the reproductive system. Loss of mating ability of older virgin males seemed to be age-related, because the reproductive system contained ample supplies of accessory gland substance and spermatozoa. Morphological changes of the reproductive system, due to mating and age, were used to infer the age and reproductive history of unknown males in a laboratory evaluation.     

Experimental defoliation affects male but not female reproductive performance of the tropical monoecious plant Croton suberosus (Euphorbiaceae)

Background and Aims

Monoecious plants have the capacity to allocate resources separately to male and female functions more easily than hermaphrodites. This can be advantageous against environmental stresses such as leaf herbivory. However, studies showing effects of herbivory on male and female functions and on the interaction with the plant''s pollinators are limited, particularly in tropical plants. Here, the effects of experimental defoliation were examined in the monoecious shrub Croton suberosus (Euphorbiaceae), a wasp-pollinated species from a Mexican tropical dry forest.

Methods

Three defoliation treatments were applied: 0 % (control), 25 % (low) or 75 % (high) of plant leaf area removed. Vegetative (production of new leaves) and reproductive (pistillate and staminate flower production, pollen viability, nectar production, fruit set, and seed set) performance variables, and the abundance and activity of floral visitors were examined.

Key Results

Defoliated plants overcompensated for tissue loss by producing more new leaves than control plants. Production of staminate flowers gradually decreased with increasing defoliation and the floral sex ratio (staminate : pistillate flowers) was drastically reduced in high-defoliation plants. In contrast, female reproductive performance (pistillate flower production, fruit set and seed set) and pollinator visitation and abundance were not impacted by defoliation.

Conclusions

The asymmetrical effects of defoliation on male and female traits of C. suberosus may be due to the temporal and spatial flexibility in the allocation of resources deployed by monoecious plants. We posit that this helps to maintain the plant''s pollination success in the face of leaf herbivory stress.     

Pollen viability reduction as a potential cost of ant association for Acacia constricta (Fabaceae)

Field studies investigating the impact of ants on the reproduction of plants bearing extrafloral nectaries have traditionally focused on seed production, a component of female fitness. The purpose of this study was to test whether ants can affect the pollen viability, a component of male fitness, when they visit flowers of the shrub Acacia constricta. Acacia constricta inflorescences hand-pollinated with flowers over which Formica perpilosa ants had crawled set significantly fewer seed pods than inflorescences hand-pollinated by control flowers that had no contact with ants. Many ant species secrete antibiotic substances onto the integument that render pollen inviable, and these secretions are probably the mechanism for reduced pollen viability in this study. The ratio of seed pods produced by self-pollinated inflorescences to those produced by cross-pollinated inflorescences was 0.16, indicating that A. constricta is largely self-incompatible. Because F. perpilosa workers forage primarily on the acacia tree under which they nest, they are unlikely to serve as efficient vectors of outcrossing. Previous work showed that A. constricta shrubs with F. perpilosa ants produce approximately twice as many seeds as similarly sized plants not so associated. The results indicate that association with F. perpilosa could cause a reproductive trade-off for A. constricta: benefits to female function may be accompanied by costs to male function. Selection to discourage ant visitation to flowers may have affected the pollination biology of this and other ant-associated plant species.     

Pollen donor performance can be consistent acrossmaternal plants in wild radish (Raphanus sativus,Brassicaceae): a necessary condition for the action of sexualselection

The possibility that sexual selection has played a role in theevolution of plant reproductive characters remains interesting, butcontroversial. One reason is that clear demonstration of the necessaryconditions for sexual selection is lacking. For sexual selection tooccur, differences in pollen donor performance must be consistent acrossmaternal plants and not be due to mechanisms such asself-incompatibility that produce interactions between maternal plantsand pollen donors. Here, I performed two experiments with wild radish totest whether differences in pollen donor performance are consistentacross maternal plants and not due to subtle effects of theincompatibility system. In the first, all maternal and paternal lineageshad different S-alleles. There were 16 maternal plants, four in each offour lineages and four pollen donors, one in each of four lineages. Rankorder of pollen donor performance, in terms of number of seeds siredafter mixed pollination, was highly consistent across maternal plantsand maternal lineages. In addition, maternal stress treatment had aneffect on mating success of pollen donors, but the effect was subtle anddid not affect the rank order of seeds sired by the four pollen donors.In the second experiment, pollinations were performed on both mature andimmature stigmas. Immature stigmas allowed some self seed set, so theincompatibility system was compromised. There was some nonrandom seedpaternity on both mature and immature stigmas. However, the amount ofnonrandom mating was less on immature stigmas. Taken together, theseexperiments show that the kind of consistent nonrandom mating necessaryfor sexual selection occurs in wild radish, but that the incompatibilitysystem and the mechanisms for sorting among compatible mates may overlapin time of development or in somepathways.     

Within‐plant variation in reproductive investment: consequences for selection on flowering time

Variation among the leaves, flowers or fruit produced by a plant is often regarded as a nuisance to the experimenter and an impediment to selection. Here, we suggest that within‐plant variation can drive selection on other plant‐level traits. We examine within‐plant variation in floral sex allocation and in fruit set and predict that such variation generates variation in male success among plants, thereby driving selection on flowering time. We tested this prediction in a simulation model estimating selection on flowering time through male fitness when floral sex allocation and/or fruit set vary directionally among flowers on plants. We parameterized the model through a quantitative literature survey of within‐plant change in sex allocation. As predicted, within‐plant variation in floral sex allocation and in fruit set probability can generate selection on flowering time through male fitness. Declining fruit set from first to last flowers on plants, as occurs in many species, selected for early flowering onset through male fitness. This result was robust to self‐incompatibility and to varying returns on male versus female investment. Selection caused by declining fruit set was strong enough to reverse the selection for late flowering that can be caused by intrafloral protandry. Our model provides testable predictions regarding selection on flowering time through male fitness. The model also establishes the intriguing possibility that within‐plant variation may influence selection on other traits, regardless of whether that variation is under selection itself.     

Strong male/male competition allows for nonchoosy females: high levels of polygynandry in a territorial frog with paternal care

Our knowledge about genetic mating systems and the underlying causes for and consequences of variation in reproductive success has substantially improved in recent years. When linked to longitudinal population studies, cross-generational pedigrees across wild populations can help answer a wide suite of questions in ecology and evolutionary biology. We used microsatellite markers and exhaustive sampling of two successive adult generations to obtain population-wide estimates of individual reproductive output of males and females in a natural population of the Neotropical frog Allobates femoralis (Aromobatidae), a pan-Amazonian species that features prolonged iteroparous breeding, male territoriality and male parental care. Parentage analysis revealed a polygynandrous mating system in which high proportions of males (35.5%) and females (56.0%) produced progeny that survived until adulthood. Despite contrasting reproductive strategies, successfully reproducing males and females had similar numbers of mating partners that sired the adult progeny (both sexes: median 2; range 1-6); the numbers of their offspring that reached adulthood were also similar (both sexes: median 2; range 1-8). Measures of reproductive skew indicate selection on males only for their opportunity to breed. Reproductive success was significantly higher in territorial than in nonterritorial males, but unrelated to territory size in males or to body size in both sexes. We hypothesize that female polyandry in this species has evolved because of enhanced offspring survival when paternal care is allocated to multiple partners.     

Production of male flowers does not decrease with plant size in insect-pollinated Sagittaria trifolia, contrary to predictions of size-dependent sex allocation

It has been proposed that relative allocation to female function increases with plant size in animalpollinated species.Previous investigations in several monoecious Sagittaria species seem to run contrary to the prediction of size-dependent sex allocation (SDS),throwing doubt on the generalization of SDS.Plant size,phenotypic gender,and flower production were measured in experimental populations of an aquatic,insect-pollinated herb Sagittaria trifolia (Alismataceae) under highly different densities.The comparison of ramets produced clonally can reduce confounding effects from genetic and environmental factors.In the high-density population,48％ of ramets were male without female flowers,but in the low-density population all ramets were monoecious.We observed allometric growth in reproductive allocation with ramet size,as evident in biomass of reproductive structures and number of flowers.However,within both populations female and male flower production were isometric with ramet size,in contrast to an allometric growth in femaleness as predicted by SDS.Phenotypic gender was not related to ramet size in either population.The results indicated that large plants may increase both female and male function even in animal-pollinated plants,pointing towards further studies to test the hypothesis of size-dependent sex allocation using different allocation currencies.     

Pollination and breeding system of the enigmatic South African parasitic plant Mystropetalon thomii (Mystropetalaceae): rodents welcome,but not needed

• Unrelated plants adapted to particular pollinator types tend to exhibit convergent evolution in floral traits. However, inferences about likely pollinators from ‘pollination syndromes’ can be problematic due to trait overlap among some syndromes and unusual floral architecture in some lineages. An example is the rare South African parasitic plant Mystropetalon thomii (Mystropetalaceae), which has highly unusual brush‐like inflorescences that exhibit features of both bird and rodent pollination syndromes.
• We used camera traps to record flower visitors, quantified floral spectral reflectance and nectar and scent production, experimentally determined self‐compatibility and breeding system, and studied pollen dispersal using fluorescent dyes.
• The dark‐red inflorescences are usually monoecious, with female flowers maturing before male flowers, but some inflorescences are purely female (gynoecious). Inflorescences were visited intensively by several rodent species that carried large pollen loads, while visits by birds were extremely rare. Rodents prefer male‐ over female‐phase inflorescences, likely because of the male flowers’ higher nectar and scent production. The floral scent contains several compounds known to attract rodents. Despite the obvious pollen transfer by rodents, we found that flowers on both monoecious and gynoecious inflorescences readily set seed in the absence of rodents and even when all flower visitors are excluded.
• Our findings suggest that seed production occurs at least partially through apomixis and that M. thomii is not ecologically dependent on its rodent pollinators. Our study adds another species and family to the growing list of rodent‐pollinated plants, thus contributing to our understanding of the floral traits associated with pollination by non‐flying mammals.

     

Production of male flowers does not decrease with plant size in insect‐pollinated Sagittaria trifolia,contrary to predictions of size‐dependent sex allocation

Abstract It has been proposed that relative allocation to female function increases with plant size in animal‐pollinated species. Previous investigations in several monoecious Sagittaria species seem to run contrary to the prediction of size‐dependent sex allocation (SDS), throwing doubt on the generalization of SDS. Plant size, phenotypic gender, and flower production were measured in experimental populations of an aquatic, insect‐pollinated herb Sagittaria trifolia (Alismataceae) under highly different densities. The comparison of ramets produced clonally can reduce confounding effects from genetic and environmental factors. In the high‐density population, 48% of ramets were male without female flowers, but in the low‐density population all ramets were monoecious. We observed allometric growth in reproductive allocation with ramet size, as evident in biomass of reproductive structures and number of flowers. However, within both populations female and male flower production were isometric with ramet size, in contrast to an allometric growth in femaleness as predicted by SDS. Phenotypic gender was not related to ramet size in either population. The results indicated that large plants may increase both female and male function even in animal‐pollinated plants, pointing towards further studies to test the hypothesis of size‐dependent sex allocation using different allocation currencies.     

Indirect evidence from DNA sequence diversity for genetic degeneration of the Y-chromosome in dioecious species of the plant Silene: the SlY4/SlX4 and DD44-X/DD44-Y gene pairs

The action of natural selection is expected to reduce the effective population size of a nonrecombining chromosome, and this is thought to be the chief factor leading to genetic degeneration of Y-chromosomes, which cease recombining during their evolution from ordinary chromosomes. Low effective population size of Y chromosomes can be tested by studying DNA sequence diversity of Y-linked genes. In the dioecious plant, Silene latifolia, which has sex chromosomes, one comparison (SlX1 vs. SlY1) indeed finds lower Y diversity compared with the homologous X-linked gene, and one Y-linked gene with no X-linked homologue has lower species-wide diversity than a homologous autosomal copy (SlAp3Y vs. SlAp3A). To test whether this is a general pattern for Y-linked genes, we studied two further recently described X and Y homologous gene pairs in samples from several populations of S. latifolia and S. dioica. Diversity is reduced for both Y-linked genes, compared with their X-linked homologues. Our new data are analysed to show that the low Y effective size cannot be explained by different levels of gene flow for the X vs. the Y chromosomes, either between populations or between these closely related species. Thus, all four Y-linked genes that have now been studied in these plants (the two studied here, and two previously studied genes, have low diversity). This supports other evidence for an ongoing degeneration process in these species.     

The search for causal traits of speciation: Divergent female mate preferences target male courtship song,not pheromones,in Drosophila athabasca species complex

Understanding speciation requires the identification of traits that cause reproductive isolation. This remains a major challenge since it is difficult to determine which of the many divergent traits actually caused speciation. To overcome this difficulty, we studied the sexual cue traits and behaviors associated with rapid speciation between EA and WN sympatric behavioral races of Drosophila athabasca that diverged only 16,000–20,000 years ago. First, we found that sexual isolation was essentially complete and driven primarily by divergent female mating preferences. To determine the target of female mate choice, we found that, unlike cuticular hydrocarbons (CHCs), male courtship song is highly divergent between EA and WN in both allopatry and sympatry and is not affected by latitudinal variation. We then used pheromone rub‐off experiments to show no effect of CHCs on divergent female mate choice. In contrast, both male song differences and male mating success in hybrids exhibited a large X‐effect and playback song experiments confirmed that male courtship song is indeed the target of sexual isolation. These results show that a single secondary sexual trait is a major driver of speciation and suggest that we may be overestimating the number of traits involved in speciation when we study older taxa.