Evolution of tolerance in an invasive weed after reassociation with its specialist herbivore

The interaction between the European wild parsnip Pastinaca sativa and its coevolved florivore the parsnip webworm Depressaria pastinacella, established in North America for over 150 years, has resulted in evolution of local chemical phenotype matching. The recent invasion of New Zealand by webworms, exposing parsnips there to florivore selection for the first time, provided an opportunity to assess rates of adaptive response in a real‐time experiment. We planted reciprocal common gardens in the USA and NZ with seeds from (1) US populations with a long history of webworm association; (2) NZ populations that had never been infested and (3) NZ populations infested for 3 years (since 2007) or 6 years (since 2004). We measured impacts of florivory on realized fitness, reproductive effort and pollination success and measured phenotypic changes in infested NZ populations relative to uninfested NZ populations to determine whether rapid adaptive evolution in response to florivory occurred. Irrespective of country of origin or location, webworms significantly reduced plant fitness. Webworms reduced pollination success in small plants but not in larger plants. Although defence chemistry remained unchanged, plants in infested populations were larger after 3–6 years of webworm florivory. As plant size is a strong predictor of realized fitness, evolution of large size as a component of florivore tolerance may occur more rapidly than evolution of enhanced chemical defence.     

Pollinators shift to nectar robbers when florivory occurs,with effects on reproductive success in Iris bulleyana (Iridaceae)

• Studies have indicated that florivory and nectar robbing may reduce reproductive success of host plants. However, whether and how these effects might interact when plants are simultaneously attacked by both florivores and nectar robbers still needs further investigation.
• We used Iris bulleyana to detect the interactions among florivory, nectar robbing and pollination, and moreover, their effects on plant reproductive success. Field investigations and hand‐pollination treatments were conducted on two experimental plots from a natural population, in which Experimental plot was protected from florivores and Control plot was not manipulated.
• The flower calyx was bitten by sawflies to consume the nectary, and three bumblebee species were pollinators. In addition, the short‐tongued pollinator, Bombus friseanus, was the only robber when there was a hole made by a sawfly. The bumblebee had significantly shortened flower handling time when robbing, as compared to legitimate visits. Pollinator visitation and seed production decreased significantly in damaged flowers. However, seed production per flower after supplementary hand‐pollination did not differ significantly between damaged and undamaged flowers. Compared to the Experimental plot, bumblebees visited fewer flowers per plant in a foraging bout in the Control plot.
• The flowers damaged by florivory allowed B. friseanus to shift to a nectar robber. Florivory and nectar robbing collectively decreased plant reproductive success by consuming nectar resources, which may reduce attractiveness to pollinators of the damaged flowers. However, the changes in pollinator behaviour might be beneficial to the plant by reducing the risk of geitonogamous mating.

     

How to be an attractive male: floral dimorphism and attractiveness to pollinators in a dioecious plant

Background  

Sexual selection theory predicts that males are limited in their reproductive success by access to mates, whereas females are more limited by resources. In animal-pollinated plants, attraction of pollinators and successful pollination is crucial for reproductive success. In dioecious plant species, males should thus be selected to increase their attractiveness to pollinators by investing more than females in floral traits that enhance pollinator visitation. We tested the prediction of higher attractiveness of male flowers in the dioecious, moth-pollinated herb Silene latifolia, by investigating floral signals (floral display and fragrance) and conducting behavioral experiments with the pollinator-moth, Hadena bicruris.     

Floral antagonists counteract pollinator‐mediated selection on attractiveness traits in the hummingbird‐pollinated Collaea cipoensis (Fabaceae)

Pollinator‐mediated selection toward larger and abundant flowers is common in naturally pollen‐limited populations. However, floral antagonists may counteract this effect, maintaining smaller‐ and few‐flowered individuals within populations. We quantified pollinator and antagonist visit rates and determined a multiplicative female fitness component from attacked and non‐attacked flowers of the Brazilian hummingbird‐pollinated shrub Collaea cipoensis to determine the selective effects of pollinators and floral antagonists on flower size and number. We predicted that floral antagonists reduce the female fitness component and thus exert negative selective pressures on flower size and number, counteracting the positive effects of pollinators. Pollinators, mainly hummingbirds, comprised 4% of total floral visitation, whereas antagonist ants and bees accounted for 90% of visitation. Nectar‐robbers involved about 99% of floral antagonist visit rates, whereas florivores comprised the remaining 1%. Larger and abundant flowers increased both pollinator and antagonist visit rates and the female fitness component significantly decreased in flowers attacked by nectar‐robbers and florivores in comparison to non‐attacked flowers. We detected that pollinators favored larger‐ and many‐flowered individuals, whereas floral antagonists exerted negative selection on flower size and number. This study confirms that floral antagonists reduce female plant fitness and this pattern directly exerts negative selective pressures on flower size and number, counteracting pollinator‐mediated selection on floral attractiveness traits.     

Florivory indirectly decreases the plant reproductive output through changes in pollinator attraction

Species often interact indirectly with each other via their traits. There is increasing appreciation of trait‐mediated indirect effects linking multiple interactions. Flowers interact with both pollinators and floral herbivores, and the flower‐pollinator interaction may be modified by indirect effects of floral herbivores (i.e., florivores) on flower traits such as flower size attracting pollinators. To explore whether flower size affects the flower‐pollinator interaction, we used Eurya japonica flowers. We examined whether artificial florivory decreased fruit and seed production, and also whether flower size affected florivory and the number of floral visitors. The petal removal treatment (i.e., artificial florivory) showed approximately 50% reduction in both fruit and seed set in natural pollination but not in artificial pollination. Furthermore, flower size increased the number of floral visitors, although it did not affect the frequency of florivory. Our results demonstrate that petal removal indirectly decreased 75% of female reproductive output via decreased flower visits by pollinators and that flower size mediated indirect interactions between florivory and floral visitors.     

Florivore impacts on plant reproductive success and pollinator mortality in an obligate pollination mutualism

Florivores are present in many pollination systems and can have direct and indirect effects on both plants and pollinators. Although the impact of florivores are commonly examined in facultative pollination mutualisms, their effects on obligate mutualism remain relatively unstudied. Here, we used experimental manipulations and surveys of naturally occurring plants to assess the effect of florivory on the obligate pollination mutualism between yuccas and yucca moths. Yucca filamentosa (Agavaceae) is pollinated by the moth Tegeticula cassandra (Lepidoptera: Prodoxidae), and the mutualism also attracts two florivores: a generalist, the leaf-footed bug Leptoglossus phyllopus (Hemiptera: Coreidae), and a specialist, the beetle Hymenorus densus (Coleoptera: Tenebrionidae). Experimental manipulations of leaf-footed bug densities on side branches of Y. filamentosa inflorescences demonstrated that feeding causes floral abscission but does not reduce pollen or seed production in the remaining flowers. Similar to the leaf-footed bugs, experimental manipulations of beetle densities within individual flowers demonstrated that beetle feeding also causes floral abscission, but, in addition, the beetles also cause a significant reduction in pollen availability. Path analyses of phenotypic selection based on surveys of naturally occurring plants revealed temporal variation in the plant traits important to plant fitness and the effects of the florivores on fitness. Leaf-footed bugs negatively impacted fitness when fewer plants were flowering and leaf-footed bug density was high, whereas beetles had a positive effect on fitness when there were many plants flowering and their densities were low. This positive effect was likely due to adult beetles consuming yucca moth eggs while having a negligible effect on floral abscission. Together, the actions of both florivores either augmented the relationship of plant traits and fitness or slightly weakened the relationship. Overall, the results suggest that, although florivores are always present during flowering, the impact of florivores on phenotypic selection in yuccas is strongly mitigated by changes in their densities on plants from year to year. In contrast, both florivores consistently influenced pollinator larval mortality through floral abscission, and H. densus beetles additionally via the consumption of pollinator eggs.     

Petunia flowers solve the defence/apparency dilemma of pollinator attraction by deploying complex floral blends

Flowers recruit floral visitors for pollination services by emitting fragrances. These scent signals can be intercepted by antagonists such as florivores to locate host plants. Hence, as a consequence of interactions with both mutualists and antagonists, floral bouquets likely consist of both attractive and defensive components. While the attractive functions of floral bouquets have been studied, their defensive function has not, and field‐based evidence for the deterrence of floral‐scent constituents is lacking. In field and glasshouse experiments with five lines of transgenic Petunia x hybrida plants specifically silenced in their ability to release particular components of their floral volatile bouquet, we demonstrate that the emission of single floral‐scent compounds can dramatically decrease damage from generalist florivores. While some compounds are used in host location, others prevent florivory. We conclude that the complex blends that comprise floral scents are likely sculpted by the selective pressures of both pollinators and herbivores.     

腐生植物无叶美冠兰食源性欺骗传粉研究

无叶美冠兰是一种典型的腐生兰科植物,为揭示该物种的自然传粉机制,拓展对兰科植物生殖特性的认识,在广西雅长兰科植物国家级自然保护区对其开展了传粉生态学观测研究。结果表明:无叶美冠兰花朵具备高度自交亲和能力,但不存在自动自花授粉机制,必须依赖外部传粉媒介把花粉送到柱头,实现有效传粉;绿彩带蜂是无叶美冠兰唯一有效传粉昆虫;传粉昆虫与花朵在与传粉功能相关的关键性状在形态上良好拟合;绿彩带蜂的访花活动主要发生在3个阶段:8.6%发生在9:00~11:30,80.2%发生在11:30~14:00,11.2%发生在14:00~15:30;花朵在中午强烈的阳光直射下挥发出香甜的气味。无叶美冠兰花朵主要通过挥发极具诱惑力的香甜气味和唇瓣上黄色的蜜导来诱导绿彩带蜂进入花朵中觅食,传粉昆虫与花朵在与传粉功能相关的关键性状在形态上良好拟合促成有效传粉,绿彩带蜂在整个传粉过程没有获得报酬,是食源性欺骗传粉机制。     

GENETICS OF PHYSIOLOGICAL AND BEHAVIORAL RESISTANCE TO HOST FURANOCOUMARINS IN THE PARSNIP WEBWORM

Depressaria pastinacella, the parsnip webworm, feeds almost exclusively on the flowers and fruits of Pastinaca sativa, the wild parsnip. Resistance to webworms in wild parsnip populations is largely attributable to genetically based variation in furanocoumarin chemistry; by differentially reducing fruit set among chemical phenotypes, parsnip webworms may act as selective agents on wild parsnip populations. To determine whether wild parsnip chemistry can act as a selective agent on webworm populations, it is necessary to establish that resistance mechanisms in the webworm to furanocoumarins are genetically based. In this study, we estimated the amount of genetic variation in behavioral and physiological responses of webworms to parsnip furanocoumarins. Virtually no variation was found among webworm families for feeding preferences for diets varying as much as fourfold in furanocoumarin content. Nor was significant variation found for mean furanocoumarin intake over the assay period, except in one case, in which maternal effects may account for differences among families. In contrast, substantial familial variation existed for cytochrome P450–mediated metabolism of bergapten and xanthotoxin, two host furanocoumarins. The presence of additive genetic variation in metabolism, and the absence of such variation in discriminative feeding behavior, suggests that adaptation to changes in furanocoumarin chemistry, resulting either from changes in the distribution of chemical phenotypes in parsnip populations or from shifts to new chemically different host plants, is likely to be facilitated by physiological rather than behavioral means.     

Pollinator response to flower color polymorphism and floral display in a plant with a single-locus floral color polymorphism: consequences for plant reproduction

Variation in flower color, particularly polymorphism, in which two or more different flower color phenotypes occur in the same population or species, may be affected or maintained by mechanisms that depend on pollinators. Furthermore, variation in floral display may affect pollinator response and plant reproductive success through changes in pollinator visitation and availability of compatible pollen. To asses if flower color polymorphism and floral display influences pollinator preferences and movements within and among plants and fitness-related variables we used the self-incompatible species Cosmos bipinnatus Cav. (Asteraceae), a model system with single-locus flower color polymorphism that comprises three morphs: white (recessive homozygous), pink (heterozygous co-dominate), and purple (dominant homozygous) flowers. We measured the preferences of pollinators for each morph and constancy index for each pollinator species, pollination visitation rate, floral traits, and female fitness measures. Flower color morphs differed in floral trait measures and seed production. Pollinators foraged nonrandomly with respect to flower color. The most frequent morph, the pink morph, was the most visited and pollinators exhibited the highest constancy for this morph. Moreover, this morph exhibited the highest female fitness. Pollinators responded strongly to floral display size, while probed more capitulums from plants with large total display sizes, they left a great proportion of them unvisited. Furthermore, total pollinator visitation showed a positive relation with female fitness. Results suggest that although pollinators preferred the heterozygous morph, they alternate indiscriminately among morphs making this polymorphism stable.     

Cheater or mutualist? Novel florivory interaction between nectar‐rich Crotalaria cunninghamii and small mammals

Animals visit flowers to access resources and by moving pollen to conspecific individuals act as pollinators. While biotic pollinators can increase the seed set of plants, other flower visitors can reduce seed set directly by damaging vital reproductive organs and indirectly by affecting the way the plant interacts with subsequent flower visitors. It is, therefore, vital to understand the varied effects of all visitors and not only pollinators on plant fitness, including those visitors that are temporally or spatially rare. We document the first known case of flower visitation by small mammals to Crotalaria cunninghamii (Fabaceae), a plant species morphologically suited to bird pollination. During a rain‐driven resource pulse in the Simpson Desert in 2011, the rodents Mus musculus (Muridae) and Pseudomys hermannsburgensis (Muridae) visited flowers to remove nectar by puncturing the calyx. We investigated the effects of this novel interaction on the reproductive output of C. cunninghamii. Compared with another recent resource pulse in 2007, plants flowering during mammal visitation had five times as many inflorescences per plant, 90% more flowers per inflorescence, and two to three times more nectar per flower, but this nectar was 30% less sugar rich. Concurrently, rodent plagues were up to three times larger during this rain‐driven resource pulse than during a previous pulse in 2007. Up to 75% of flowers had evidence of small mammal florivory, but this was not necessarily destructive, as up to 90% of fruit had the remains of florivory. Through a series of exclusion experiments, we found that small mammal florivory did not directly reduce seed set. We conclude that rain‐driven resource pulses led to a unique combination of events that facilitated the novel florivory interaction. Our findings emphasize the dynamic nature of biotic interactions and the importance of testing the role of all visitors to pollination services.     

Effects of experimental manipulation of inflorescence size on pollination and pre-dispersal seed predation in the hummingbird-pollinated plant Ipomopsis aggregata

Large floral displays should theoretically provide advantages to plants through increased pollinator visitation and resulting fruit and seed set. However empirical tests of the response of pollinators to floral display size have been limited by a lack of direct experimentation, and the results of such studies have been equivocal. In addition, other selective agents such as pre-dispersal seed predators might modulate effects of floral display on pollination. By artificially altering flower number, we examined the direct effects of floral display in the monocarpic herb, Ipomopsis aggregata (Polemoniaceae), on visitation rates by broad-tailed and rufous hummingbird pollinators, as well destruction of fruits by a pre-dispersal seed predator (Hylemya: Anthomyiidae). In addition, we quantified the ultimate effects of flower number on female reproductive success. Plants with larger floral displays were most likely to be visited first in any given foraging bout (P < 0.01). As expected, plants with more flowers received more total flower visits. However, we found no gain in the proportion of flowers visited for many- versus few-flowered plants, or the total number of approaches/hour. In fact, a significantly greater percentage of flowers were visited on few-flowered plants. Plants did not compensate for our reduction in flowers by increasing investment in the number or proportion of flowers that set fruit, the number of seeds/fruit, or seed weight. Pre-dispersal seed predation was greater for many- than for few-flowered plants (P < 0.001), but this did not offset the potential fitness gains of producing large displays. Our data support the hypothesis that large floral displays function primarily in long-distance attraction of pollinators, and enhance maternal success. Received: 21 March 1996 / Accepted: 24 October 1996     

Impact of reassociation with a coevolved herbivore on oviposition deterrence in a hostplant

Although selection by herbivores for increased feeding deterrence in hostplants is well documented, selection for increased oviposition deterrence is rarely examined. We investigated chemical mediation of oviposition by the parsnip webworm (Depressaria pastinacella) on its principal hostplant Pastinaca sativa to determine whether ovipositing adults choose hostplants based on larval suitability and whether hostplants experience selection for increased oviposition deterrence. Webworms consume floral tissues and florivory selects for increased feeding deterrents; moths, however, oviposit on leaves of pre-bolting plants. Exclusive use of different plant parts for oviposition and larval feeding suggests oviposition should select for increased foliar deterrents. Recent webworm colonization of New Zealand (NZ) allowed us to assess phenotypic changes in foliar chemicals in response to webworm oviposition. In a common garden experiment, we compared NZ populations with and without a history of infestation from 2004 to 2006 for changes in leaf chemistry in response to oviposition. Three leaf volatiles, cis- and trans-ocimene, and β-farnesene, elicit strong responses in female moth antennae; these compounds were negatively associated with oviposition and are likely oviposition deterrents. Leaf β-farnesene was positively correlated with floral furanocoumarins that deter florivory; greater oviposition on plants with low floral furanocoumarins indicates that moths preferentially oviposit on parsnips most suitable for larval growth. Unlike florivory, high oviposition on leaves did not lower plant fitness, consistent with the fact that NZ parsnip foliar chemistry was unaffected by 3–6 years of webworm infestation. Thus, in this system, selection by ovipositing moths on foliar chemistry is weaker than selection by larvae on floral chemistry.     

Florivory: the intersection of pollination and herbivory

Plants interact with many visitors who consume a variety of plant tissues. While the consequences of herbivory to leaves and shoots are well known, the implications of florivory, the consumption of flowers prior to seed coat formation, have received less attention. Herbivory and florivory can yield different plant, population and community outcomes; thus, it is critical to distinguish between these two types of consumption. Here, we consider the ecological and evolutionary consequences of florivory. A growing number of studies recognize that florivory is common in natural systems and in some cases surpasses leaf herbivory in magnitude and impact. Florivores can affect male and female plant fitness via direct trophic effects and through altered pathways of species interactions. In particular, florivory can affect pollination and have consequences for plant mating and floral sexual system evolution. Plants are not defenceless against florivore damage. Concepts of resistance and tolerance can be applied to plant–florivore interactions. Moreover, extant theories of plant chemical defence, including optimal defence theory, growth rate hypothesis and growth differentiation–balance hypothesis, can be used to make testable predictions about when and how plants should defend flowers against florivores. The majority of the predictions remain untested, but they provide a theoretical foundation on which to base future experiments. The approaches to studying florivory that we outline may yield novel insights into floral and defence traits not illuminated by studies of pollination or herbivory alone.     

Florivores prefer white versus pink petal color morphs in wild radish, Raphanus sativus

Many hypotheses suggest that pollinators act to maintain or change floral color morph frequencies in nature, although pollinator preferences do not always match color morph frequencies in the field. Therefore, non-pollinating agents may also be responsible for color morph frequencies. To test this hypothesis, we examined whether Raphanus sativus plants with white flowers received different amounts of florivory than plants with pink flowers, and whether florivores preferred one floral color over the other. We found that white-flowered plants received significantly more floral damage than pink-flowered plants in eight populations over 4 years in northern California. Both generalists and specialists on Brassicaceae preferred white petals in choice and short-term no choice tests. In performance tests, generalists gained more weight on white versus pink petals whereas specialists gained similar amounts of weight on pink and white morphs. Because our results suggest that florivores prefer and perform better on white versus pink flowers, these insects may have the opportunity to affect the frequency of color morphs in the field.     

Florivores decrease pollinator visitation in a self-incompatible plant

Different biotic interactions may influence one another to produce complex patterns of direct and indirect effects, which together influence plant reproductive success. However, so far most studies on plant-animal interactions have focused on single interactions in isolation. In this study, we studied the effect of florivory by the weevil Cionus nigritarsis on pollinator visitation rate in the self-incompatible perennial herb Verbascum nigrum by combining observations of florivory and pollination in natural populations with records of pollinator visitation to plants with different levels of experimentally inflicted damage.Increasing levels of damage through either natural or simulated florivory resulted in fewer pollinator visits per plant and per flower. As expected, the magnitude of the indirect effect of florivory on pollinator visitation was proportional to the intensity of florivory. Our results indicate that biotic non-pollinating agents, such as florivores, may induce substantial changes in pollinator availability. Therefore, studies addressing different plant-animal interactions in parallel are necessary to better comprehend the factors influencing the reproductive performance and demography of flowering plants.     

Flower color change accelerated by bee pollination in Tibouchina (Melastomataceae)

Floral color changes are common among Melastomataceae and have been interpreted as a warning mechanism for bees to avoid old flowers, albeit increasing long-distance flower display. Here the reproductive systems of Tibouchina pulchra and T. sellowiana were investigated by controlled pollinations. Their pollinators were identified, and experiments on floral color and fragrance changes were conduced to verify if those changes affect the floral visitation. Both Tibouchina species are self compatible. The flowers lasted three days or more, and the floral color changed from white in the 1st day to pink in the following days. Pollen deposition on stigma induced floral color change. The effectiveness of the pollination is dependent on bees’ size; only large bees were regarded as effective pollinators. In experimental tests, the bees in T. pulchra preferred the natural white flowers while the visitors of T. sellowiana were attracted by both natural and mimetic 1st-day flowers (2nd-day flowers with experimentally attached 1st-day flower petals). During the experiments on floral fragrance, the bees visited both natural and mimetic 1st-day flowers (2nd-day flowers with 1st-day flower scents). In both experiments, the bees avoided natural 2nd-day flowers, but seldom visited modified 2nd-day flowers. The attractiveness of T. pulchra and T. sellowiana flowers cannot be attributed exclusively to the color or the fragrance separately, both factors seemingly act together.     

A garden study of the effects of ultraviolet-B radiation on pollination success and lifetime female fitness in Brassica

While a large number of studies have examined the effects of increased ultraviolet-B radiation (UV-B) on growth and physiological function of plants, UV-B effects on pollination success and fitness are poorly understood. To examine this question, we measured growth, timing of flowering, pollination success, production of pollen, ovules, flowers, fruits, and seeds, and quality of offspring produced by Brassica nigra and B. rapa in a garden experiment. A total of 313 plants of the two species were randomly divided into two treatment groups. One group received only natural ambient levels of UV-B, while the other received an artificially enhanced UV-B dose. Fitness of B. nigra declined at the higher UV-B dose while B. rapa fitness did not change. One possible cause of this result was a shift in the relative attractiveness of the two species to pollinators: visitation to B. nigra declined at the high UV-B dose while B. rapa visitation increased. Received: 25 October 1996 / Accepted: 27 March 1997     

兰科植物欺骗性传粉

植物与传粉动物的互利关系在生态系统中非常普遍。然而,有许多植物不为传粉者提供任何报酬,而是利用各种欺骗方式诱骗昆虫拜访,从而实现传粉,即欺骗性传粉。兰科是被子植物大科之一,其高度特化的繁殖器官和适应于昆虫传粉的精巧结构令人称奇。进化论创始人达尔文描述了许多兰花与昆虫精巧的传粉系统,但他忽视了欺骗性传粉的存在。事实上,近1/3的兰科植物都依赖于欺骗性传粉。欺骗性传粉可能是导致兰科植物多样性的重要原因之一。兰花利用或操作昆虫觅食、交配、产卵和栖息等行为,演化出各种各样的欺骗性传粉机制,常见的类型包括泛化的食源性欺骗、Batesian拟态、性欺骗、产卵地拟态和栖息地拟态。花的颜色、形态和气味在欺骗性传粉的成功实现中起到了重要作用。欺骗性兰花与传粉昆虫之间的演化可能是不同步的,兰花追踪昆虫的行为信号而发生分化,然而欺骗性传粉可能对昆虫造成一定的伤害,从而对昆虫也施加选择压力。由于昆虫的学习行为,欺骗性的兰花一般具有低的昆虫拜访率和结实率,其繁殖成功率受各种因素的影响。欺骗性加剧了兰花对传粉昆虫的依赖,使其具有更高的灭绝风险,传粉生物学的研究能为兰科植物的有效保护提供指导。在欺骗性传粉系统中,有报酬的伴生植物、拟态模型和其他拟态信号提供者对传粉成功有重要影响。因此,研究欺骗性传粉兰花、传粉昆虫和相关的生物和生态因子的网状进化关系具有重要理论和实践意义。     

Fitness consequences of a clock pollinator filter in Nicotiana attenuata flowers in nature

Nicotiana attenuata flowers, diurnally open,emit scents and move vertically to interact with nocturnal hawkmoth and day-active hummingbird pollinators. To examine the fitness consequences of these floral rhythms, we conducted pollination trials in the plant's native habitat with phase-shifted flowers of plants silenced in circadian clock genes. The results revealed that some pollination benefits observed under glasshouse conditions were not reproduced under natural field conditions. Floral arrhythmicity increased pollination success by hummingbirds, while reducing those by hawkmoths in the field. Thus, floral circadian rhythms may influence a plant's fitness by filtering pollinators leading to altered seed set from outcrossed pollen.