Comparison of delayed female mating on reproductive biology of codling moth and obliquebanded leafroller

Delay of mating was examined as a possible mechanism for population decreases associated with mating disruption for codling moth, Cydia pomonella L., and obliquebanded leafroller, Choristoneura rosaceana (Harris) (Lepidoptera: Tortricidae). We examined the effect of delaying female mating 0, 2, 4, or 6 d while holding male age constant on life table parameters of both species. We found that increasing delays in mating were accompanied by two responses: (1) an increase in the percentage of sterile pairs and (2) a reduction in net reproductive rate and population growth unrelated to sterility. On a percentage basis, obliquebanded leafroller population growth was more strongly affected than codling moth. However, the net fertility rate of obliquebanded leafroller was nearly eight-fold higher than that of codling moth, so that obliquebanded leafroller females that experienced a 4-d delay in mating had nearly the same reproductive rate as codling moth females that experienced no delay. Leslie matrix simulations using life tables with field-based adult longevity estimates showed that codling moth females experiencing >2-d delay in mating resulted in decreases in population density or extinction within two generations. In contrast, obliquebanded leafroller females delayed <6 d showed rapid population growth that decreased as female age at mating increased; only the 6-d delay treatment resulted in decreased population levels. Our results indicate that obliquebanded leafroller females must on average experience a much longer delay in mating to significantly reduce population growth compared with codling moth females, suggesting that delay of mating likely plays a greater role in codling moth mating disruption than for obliquebanded leafroller.     

延迟交配对山楂叶螨繁殖的影响

为了探索雌螨延迟交配对整个种群的负面效应, 采用叶碟饲养法, 在室内条件下研究了延迟交配对山楂叶螨Tetranychus viennensis Zacher繁殖及种群增长的影响。结果表明: 雌螨延迟交配主要影响寿命、产卵量, 进而影响种群增长率; 随着雌螨交配时间的延迟, 影响的程度逐渐加剧。交配延迟达到或超过7 d, 雌螨的寿命比对照延长20.17%, 产卵量比对照下降26.74%, 但对后代的孵化率、存活率无明显影响。对生命表参数的分析结果表明, 雌螨交配延迟达到或超过7 d, 会导致净生殖率显著下降、平均世代周期历期显著延长, 而内禀增长率则在交配延迟3 d时显著降低。未经交配的雌螨只能营孤雌生殖, 寿命延长了31.14%, 产卵量减少了30.08%。营孤雌生殖的雌螨可以通过与其后代回交而实现两性生殖。结果提示延迟交配会导致山楂叶螨的繁殖力降低。     

Life history changes in Trogoderma variabile and T. inclusum due to mating delay with implications for mating disruption as a management tactic

Controlling postharvest pest species is a costly process with insecticide resistance and species‐specific control requiring multiple tactics. Mating disruption (MD) can be used to both decrease a female's access to males and delay timing of mating and decreases overall mating success in a population and population growth rate. Development of new commercially available MD products requires an understanding of life history parameters associated with mating delay. These can provide information for targeting proportions of reproducing individuals using MD. After delaying mating for females of two closely related beetle species, Trogoderma variabile and T. inclusum, we surveyed survivorship, number of eggs laid, and number of progeny emerged. With increases in mating age, total number of eggs laid and total number of progeny emerged significantly declined over time. T. inclusum typically had greater numbers of eggs laid and progeny emerged compared to T. variabile as female age at mating increased, suggesting that T. inclusum may be more resistant to long‐term delays in mating. Life span showed an increase as mating age increased but life span significantly decreased almost immediately following mating. Simulations depicting multiple distributions of mating within a population suggest that in a closed population, high levels of mating delay significantly reduced reproductive growth rates. Although reproductive growth rates were decreased with increased mating age, they are still large enough to maintain populations. This study highlights the differences in life history between two closely related species, suggesting that T. inclusum outperforms T. variabile over the course of a life span, but T. variabile has better reproductive capabilities early in life. MD may also be a viable component of a pest management system for these two species as it significantly decreased overall reproductive output and population growth.     

Modeling the interaction of physiological time, seasonal weather patterns, and delayed mating on population dynamics of codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae)

The effect of delaying female mating on population growth in codling moth (Cydia pomonella (L.)) was found to act on a physiological time (degree-day) basis and was predictable using a simple quadratic equation. When combined with previous work on degree-day based mortality, we were able to evaluate how the magnitude of population reduction and survival varied between sites, years, and generations at locations in California, Michigan, Pennsylvania and Washington states. In general, reductions in population growth associated with females mating 1–3 days after emergence were greater in warmer areas and during warmer times of the year. In any given year and location, the temperature profiles during peak flight were crucial in determining the population reductions, but over an 11-year period, the average seasonal temperature profile was more important. During the overwintering generation, conditions were relatively mild in all locations and only minor differences were observed in population growth rates between locations. Populations experiencing 1–3 days delay in female mating were reduced 8, 19 and 32 % compared to populations experiencing no delay, respectively. During the first summer generation, population reductions doubled compared to those seen in the overwintering generation. During the second summer flight, reductions in population growth rate at the three cooler locations decreased, while they increased in the warmer California location. Overall, the results show delayed mating can help understand how population growth is related to environmental conditions experienced naturally by insect populations and will help guide studies of the mechanisms of mating disruption, a technique used for pest suppression in agricultural and forest systems.     

Comparative efficacy of two controlled-release gypsy moth mating disruption formulations

The effects of aerial applications of the gypsy moth sex pheromone, disparlure, on mating disruption and suppression of growth of populations of the gypsy moth, Lymantria dispar (L.), were investigated. Two formulations of disparlure, plastic laminate flakes applied in a single application and polymethacrylate beads applied in two applications, were compared in two separate tests conducted in 1993 and 1994. The beads were applied in two applications spaced 2 weeks apart because preliminary tests had indicated that they released pheromone too rapidly to maintain adequate emission rates throughout the period of male flight. In 1993, the flakes were applied at a rate of 50 g a.i./ha, and the beads were applied at a rate of 15 g a.i./ha for each application. In 1994, the flakes were applied at a rate of 75 g a.i./ha and the beads were applied at rates of 32.5 and 42.5 g a.i./ha for the two applications. Beads with larger average particle size were used in 1994 to prolong disparlure release. The treatments applied in 1993 resulted in >97% reduction in mating and >82% suppression of population growth in the following year. Because of a 1995 collapse of gypsy moth populations in the vicinity of the tests, reliable population growth data were not available for the treatments applied in 1994, but significant mating disruption did occur under both treatments. Based on measurements of residual disparlure after field aging, the flakes released 32 and 48% of their disparlure content during the 6 weeks of male moth flight in 1993 and 1994, respectively. The smaller beads used in 1993 released 75% of their disparlure content, and the larger beads used in 1994 released 52% of their disparlure content, during the 6 weeks of male flight. The biological efficacy data suggest that the bead and flake formulations, as applied in these tests, have similar effects on gypsy moth mating disruption and subsequent population growth. Based on the observed release rates from both 1993 and 1994, a single application of the beads would provide emission rates equal to or greater than those provided by the flakes when applied at an equal dose.     

Delayed mating and reproduction in the autumn gum moth Mnesampela privata

• 1 The success of mating disruption using synthetic sex pheromones depends not only on preventing mating, but also on delaying mating in the target insect. Using the geometrid pest of Eucalyptus plantations, Mnesampela privata (Guenée), we determined the effect of delaying mating when imposed on males only, females only or on both sexes simultaneously, for 1, 3, 5 and 7 days.
• 2 Delayed mating had a significant negative impact on reproduction, with a 0.89‐fold decrease in the likelihood of mating and a 0.67‐fold decrease in the likelihood of that mating resulting in fertile eggs for every day that mating is delayed. A mating delay of 7 days reduced the mean number of viable eggs laid to 4–13% of that laid by moths paired immediately after emergence.
• 3 Male only imposed mating delays had a significantly lower effect on reducing the likelihood of pairs mating than when both sexes were delayed. A delay imposed on one sex only or on both sexes simultaneously, however, had a similar negative impact on the proportion of fertile matings as well as on the total number of fertile eggs laid.
• 4 Longevity of mated female and male M. privata was significantly different between mating delay treatments, with a significant decline in female longevity when they mated with older males.
• 5 The underlying mechanisms causing a decline in female reproductive output when a mating delay was imposed on males versus females are discussed in relation to the reproductive biology of M. privata and the potential of using mating disruption strategies to control populations in Eucalyptus plantations.

     

Reproductive performance and longevity of female European corn borer,Ostrinia nubilalis: effects of multiple mating,delay in mating,and adult feeding

In a recent study on the pheromone-mating disruption of the European corn borer, Ostrinia nubilalis (Lepidoptera: Crambidae), we recorded a significant reduction in mating frequency, as well as a marked delay in mating in feral females captured in disruptant-treated fields. In order to be able to accurately interpret the results in terms of effective population control, the current study was undertaken on the effects of multiple matings and a delay in mating on reproductive performance. Female O. nubilalis that mated at least twice had significantly higher fecundity and fertility, compared with once-mated females. In addition, multiple-mated females deposited a significantly larger portion of their egg complement, relative to single-mated or unmated females. Females that experienced a 3-day delay in mating showed a significant reduction in fecundity compared with females that mated soon after emergence. A 1-week delay in mating resulted in a further reduction in fecundity and a near zero fertility. The effect of sugar feeding on reproduction was not significant. In general, unmated females lived longer than mated females, and sugar-fed mated females had a higher longevity than water-fed mated females.     

Delayed and carryover effects of salinity on flowering in Iris hexagona (Iridaceae)

Saltwater intrusion into wetland ecosystems has destroyed or damaged many native plant populations. Iris hexagona is a salt-sensitive species that exhibits intraspecific variation in salinity tolerance. To investigate the effect of salinity on flowering, we exposed I. hexagona collected from natural populations to salt treatments in a common garden. Experimental salinity additions strongly delayed flowering phenology, but the effect was not apparent until the second year, when less than 4 g/L NaCl delayed flowering up to 3 d. In the field, soil salinity and flowering phenology varied substantially within I. hexagona populations. Iris flowers are receptive to pollinators for 2 d or less, therefore a 3-d delay could affect outcrossing dynamics, and ultimately, the evolutionary ecology of iris populations. Salinity also had a carryover effect; prior salinity exposure delayed flowering in irises that had been replanted in freshwater conditions for 6 mo. This is an important result because it suggests that episodic stress (such as tropical storms) can influence performance well after the stress has disappeared. Our research further underscores the importance of long-term studies because a 1-yr experiment would have failed to reveal the strong effects of salinity that emerged in the second year.     

Delayed mating reduces reproductive output of female European grapevine moth,Lobesia botrana (Lepidoptera: Tortricidae)

Virgin females of Lobesia botrana Denis & Schiffermüller were mated at ages of 1, 3, 5, 8, 12 and 16 days and the effect of mating delay on reproductive output assessed. Delayed mating did not affect female mating success but fertilization was reduced in 16-day-old females. Increased mating delays substantially affected daily oviposition pattern and resulted in a significant reduction of both fecundity and fertility, so that mean number of viable eggs laid decreased from 150 to 22 in 1- and 16-day-old mated females, respectively. Heavier females were more constrained than lighter ones by mating delays and female reproductive efficiency (no. viable eggs/female body weight) was also significantly reduced. Female longevity significantly increased and oviposition period gradually declined with mating delay. The number of viable eggs was positively correlated with both female weight and oviposition period; female longevity and female weight were also significantly correlated. However, the significance of these correlations declined with increased mating delay. Results overall indicated that mating delay drastically reduces female L. botrana reproductive output. The implications of delayed mating of females are discussed from an ecological perspective in relation to L. botrana control using mating disruption.     

The interactive effects of herbivory and mixed mating for the population dynamics of Impatiens capensis

In this study, we examine the demographic consequences of mixed mating and explore the interactive effects of vegetative herbivory and mating system for population dynamics of Impatiens capensis, a species with an obligate mixed mating system (i.e., individuals produce both obligately selfing cleistogamous and facultatively outcrossing chasmogamous flowers). In two natural populations, we followed seeds derived from cleistogamous and chasmogamous flowers subject to different herbivory levels throughout their life cycle. Using a mating system-explicit projection matrix model, we found that mating system types differed in important vital rates. Cleistogamous individuals had higher rates of germination than did chasmogamous individuals, whereas chasmogamous individuals expressed a fecundity advantage over cleistogamous individuals. In addition, population growth was most sensitive to changes in vital rates of cleistogamous individuals, indicating the demographic importance of selfing for these populations. Herbivory also had demographic consequences; a 33%-49% reduction in herbivory caused the population growth rates to increase by 104%-132%, primarily because of effects on vital rates of selfed individuals. Our results not only uncover a novel consequence of mating system expression, that is, mating system influences population dynamics, but also shed light on the role of herbivores in maintaining mixed mating.     

ROLE OF NUTRIENT FLUCTUATIONS AND DELAYED DEVELOPMENT IN GAMETOPHYTE REPRODUCTION BY MACROCYSTIS PYRIFERA (PHAEOPHYCEAE) IN SOUTHERN CALIFORNIA1

Organisms occurring in environments subject to severe disturbance and/or periods of poor environmental quality that result in severe adult mortality can survive these periods by relying on alternate life stages that delay their development in a resistant state until conditions improve. In the northeast Pacific, the forest‐forming giant kelp Macrocystis pyrifera (L.) C. Agardh periodically experiences widespread adult mortality during extended periods of extremely low nutrients and high temperatures, such as those associated with El Niño. Recovery following these periods is hypothesized to occur from microscopic life stages that delay their development until the return of favorable conditions. In the laboratory, we experimentally examined the environmental conditions responsible for regulating delayed development of the microscopic stages of M. pyrifera from Southern California, USA. Nutrients controlled the delay and resumption of gametophyte growth and reproduction, perhaps linked to the large fluctuations in nutrients occurring seasonally and interannually in this region. Although growth of gametophytes proceeded in the virtual absence of nitrate, both nitrate and other trace nutrients were necessary for gametogenesis. Upon exposure to elevated nutrients, delayed gametophytes produced sporophytes more quickly (5–20 d) and at smaller sizes (10–200 μm) than gametophytes that had never been delayed (18–80 d, 80–400 μm, respectively), reducing negative density‐dependent effects. This finding demonstrates that delayed gametophytes of M. pyrifera rapidly utilize increased resources to consistently produce sporophytes. Further work is needed to assess their potential role in population recovery following periods of poor environmental quality.     

Effects of delayed mating on reproductive output of female oriental beetle Anomala orientalis (Coleoptera: Scarabaeidae)

1 Although management of the oriental beetle Anomala orientalis (Waterhouse) by mating disruption shows promise across a range of agricultural systems, relatively little is known about aspects of the reproductive biology of this species relevant to its management. We studied the effects of delayed mating on several aspects of the oviposition behaviour and biology of the oriental beetle using females mated in the laboratory at 4–13 days posteclosion. 2 Females exhibited a gradual decline in fecundity with increased age at mating that was largely a function of a decline in duration of the oviposition period, as well as lower female fertility: females mated at 11 days were less likely to lay any fertile eggs. However, egg fertility did not vary with female age at mating. 3 Because mating delay did not affect longevity, females mated at older ages experienced decreased oviposition periods; however, females laid more eggs per day with increased age at mating, which partially offset shorter oviposition periods. 4 A mating delay of ≥ 6 days relative to females mated within the first day of reaching sexual maturity resulted in an approximately 35–50% lower mean fecundity. 5 These results suggest that, for mating disruption to be a successful management tool for the oriental beetle, mating must be prevented rather than delayed. We compare the findings of the present study with the published research on delayed mating in moths and discuss the importance of these results in relation to management of the oriental beetle using female sex pheromones.     

Selection for mating propensity in irradiated populations of the cotton boll weevil

Summary Twelve generations of family selection for 10-day post-irradiation male mating propensity resulted in significant divergence between the selected and unselected control populations. Much of this divergence was the result of a decline in the control population which was believed to have been a function of both inbreeding and environmental effects. Significant correlated responses as measured by differences in the two populations for linear time trends of performance on generations of selection were observed for 10-day post-irradiation survival, percent survivors mating at 10 days, and 7-day egg production of unirradiated females.     

Demographic stochasticity, allee effects, and extinction: the influence of mating system and sex ratio

Demographic stochasticity has a substantial influence on the growth of small populations and consequently on their extinction risk. Mating system is one of several population characteristics that may affect this. We use a stochastic pair-formation model to investigate the combined effects of mating system, sex ratio, and population size on demographic stochasticity and thus on extinction risk. Our model is designed to accommodate a continuous range of mating systems and sex ratios as well as several levels of stochasticity. We show that it is not mating system alone but combinations of mating system and sex ratio that are important in shaping the stochastic dynamics of populations. Specifically, polygyny has the potential to give a high demographic variance and to lower the stochastic population growth rate substantially, thus also shortening the time to extinction, but the outcome is highly dependent on the sex ratio. In addition, population size is shown to be important. We find a stochastic Allee effect that is amplified by polygyny. Our results demonstrate that both mating system and sex ratio must be considered in conservation planning and that appreciating the role of stochasticity is key to understanding their effects.     

Culturally transmitted paternity beliefs and the evolution of human mating behaviour

Recent anthropological findings document how certain lowland South American societies hold beliefs in 'partible paternity', which allow children to have more than one 'biological' father. This contrasts with Western beliefs in 'singular paternity', and biological reality, where children have just one father. Here, mathematical models are used to explore the coevolution of paternity beliefs and the genetic variation underlying human mating behaviour. A gene-culture coevolutionary model found that populations exposed to a range of selection regimes typically converge on one of two simultaneously stable equilibria; one where the population is monogamous and believes in singular paternity, and the other where the population is polygamous and believes in partible paternity. A second agent-based model, with alternative assumptions regarding the formation of mating consortships, broadly replicated this finding in populations with a strongly female-biased sex ratio, consistent with evidence for high adult male mortality in the region. This supports an evolutionary scenario in which ancestral South American populations with differing paternity beliefs were subject to divergent selection on genetically influenced mating behaviour, facilitated by a female-biased sex ratio, leading to the present-day associations of female control, partible paternity and polygamy in some societies, and male control, singular paternity and monogamy in others.     

Half-sib mating structures

All ways in which all matings in a population can be between half-sibs under a generalization of regular systems of inbreeding are characterized for both finite and infinite populations. A model of random half-sib mating is developed and analyzed, and the asymptotic configuration of populations subject to it is described. The classical model of half-sib mating which ensues from the standard definition of regular systems of inbreeding is only one of many ways a population can propagate by half-sib mating, and a wide range of genetic identity is possible dependent on which half-sib mating structure governs a population.     

水稻二化螟的交配行为

在室内条件下,对水稻二化螟Chilo suppressalis的交配行为及能力进行了研究.结果表明：大多数二化螟雌蛾一生只交配一次,平均0.92次;而雄蛾具有多次交配能力,最多达4次,平均2.72次.二化螟雌蛾的日龄影响其交配率、交配起始时间和持续时间,随二化螟雌蛾日龄的增加,其交配率逐渐下降,交配起始时间逐渐提前,而交配持续时间逐渐上升.相反,二化螟雄蛾日龄对其交配率、交配起始时间和持续时间没有明显影响.交配日龄对二化螟雌蛾的生殖力也存在显著影响,随着二化螟雌蛾交配日龄的增加,雌蛾产卵量下降,卵孵化率降低,产卵期缩短,它们都与雌蛾交配日龄存在显著的负相关;而雌蛾产卵前期和雌蛾寿命随雌蛾交配日龄的增加而延长,与雌蛾交配日龄存在显著的正相关.但二化螟雄蛾交配日龄对雌蛾的生殖力没有明显影响,二化螟雄蛾一生都具有较强的交配繁殖能力.同时,不同交配史的雄蛾与雌蛾交配,对雌蛾的生殖力也没有显著影响.表明二化螟的交配活动是由雌蛾主导控制的.最后,对这些结果在二化螟性信息素防治中应用的可行性进行了探讨.在应用性信息素控制二化螟的实践中,可以在两方面取得实效,一是性信息素可以阻碍雌雄之间正常交配,降低交配率;二是可以推迟二化螟雌虫的交配,使其产卵量和卵孵化率降低.     

Herbivory and competition interact to affect reproductive traits and mating system expression in Impatiens capensis

As a step toward understanding how community context shapes mating system evolution, we investigated the combined role of two plant antagonisms, vegetative herbivory and intraspecific competition, for reproduction and mating system expression (relative production of selfing, cleistogamous and facultatively outcrossing, chasmogamous flowers and fruits) of Impatiens capensis. In a survey of I. capensis populations, we found that vegetative herbivory and intraspecific competition were positively correlated. In a greenhouse experiment where leaf damage and plant density were manipulated, multispecies interactions had dramatic effects on reproductive and mating system traits. Despite having additive effects on growth, herbivory and competition had nonadditive effects for mating system expression, chasmogamous fruit production, flower number and size, and cleistogamous flower production. Our results demonstrate that competitive interactions influence the effect of herbivory (and vice versa) on fitness components and mating system, and thus antagonisms may have unforeseen consequences for mating system evolution, population genetic diversity, and persistence.     

Effect of mating delay on the reproductive performance of Cnephasia jactatana (Lepidoptera: Tortricidae)

The leafroller species, Cnephasia jactatana Walker, is an important pest of kiwifruit in New Zealand. The effect of mating delay on its reproductive performance was investigated in the laboratory to provide information for the development of pheromonal pest control measures such as mating disruption. Reproductive performance of both sexes is adversely affected by mating delay. Females are more severely affected by mating delay than males in terms of reproductive potential. Delaying mating in females for 3 and 4 d reduced the reproductive potential by 29 and 88%, respectively. It is suggested that mating disruption may have potential for the control of this species.     

Inbreeding depression and mixed mating in Leptosiphon jepsonii: a comparison of three populations

BACKGROUND AND AIMS: Inbreeding depression is thought to play a central role in the evolution and maintenance of cross-fertilization. Theory indicates that inbreeding depression can be purged with self-fertilization, resulting in positive feedback for the selection of selfing. Variation among populations of Leptosiphon jepsonii in the timing and rate of self-fertilization provides an opportunity to study the evolution of inbreeding depression and mating systems. In addition, the hypothesis that differences in inbreeding depression for male and female fitness can stabilize mixed mating in L. jepsonii is tested. METHODS: In a growth room experiment, inbreeding depression was measured in three populations with mean outcrossing rates ranging from 0.06 to 0.69. The performance of selfed and outcrossed progeny is compared at five life history stages. To distinguish between self-incompatibility and early inbreeding depression, aborted seeds and unfertilized ovules were counted in selfed and outcrossed fruits. In one population, pollen and ovule production was quantified to estimate inbreeding depression for male and female fitness. KEY RESULTS: Both prezygotic barriers and inbreeding depression limited self seed set in the most outcrossing population. Cumulative inbreeding depression ranged from 0.297 to 0.501, with the lowest value found in the most selfing population. Significant inbreeding depression for early life stages was found only in the more outcrossing populations. Inbreeding depression was not significant for pollen or ovule production. CONCLUSIONS: The results provide modest support for the hypothesized relationship between inbreeding depression and mating systems. The absence of early inbreeding depression in the more selfing populations is consistent with theory on purging. Differences in male and female expression of inbreeding depression do not appear to stabilize mixed mating in L. jepsonii. The current estimates of inbreeding depression for L. jepsonii differ from those of previous studies, underscoring the effects of environmental variation on its expression.