Analyses of nine years of citizen-based biological control monitoring of Dalmatian toadflax, <Emphasis Type="Italic">Linaria dalmatica</Emphasis> (Plantaginaceae) in Idaho,USA

Dalmatian toadflax has been a target for biological control in North America since the 1960s. The stem-mining weevil Mecinus janthiniformis was first released in Canada and the western United States in the mid-1990s. Since 2007, a citizen-based monitoring program in Idaho, USA has supplemented data collection to help evaluate the impact of M. janthiniformis on Dalmatian toadflax abundance and assess changes in the surrounding plant community. We monitored and analysed trends in toadflax, weevil, and the plant community abundance following weevil releases at the regional and site level (34 sites) across the state of Idaho, USA. Significant declines in toadflax cover and stem density were recorded across the majority of sites. Weevil populations have established at all release sites. The mechanistic model indicated that the population dynamics of toadflax at our sites are negatively affected by M. janthiniformis abundance. When averaged across the region, 15 years after weevil release, Dalmatian toadflax stem density and cover declined by 93 and 84%, respectively. We observed significant declines in toadflax abundance in over 75% of the sites. Changes to the surrounding plant community following weevil releases were less consistent among sites. At the regional scale we found evidence for an overall increase in average cover of native perennial grasses and other exotic weeds (primarily annual grasses and exotic forbs) but a decline in native forbs.     

Herbivory differentially affects male and female reproductive traits of Cucumis sativus

Herbivory is an important selection pressure in the life history of plants. Most studies use seed or fruit production as an indication of plant fitness, but the impact of herbivory on male reproductive success is usually ignored. It is possible that plants compensate for resources lost to herbivory by shifting the allocation from seed production to pollen production and export, or vice versa. This study examined the impact of herbivory by Helix aspersa on both male and female reproductive traits of a monoecious plant, Cucumis sativus. The effects of herbivory on the relative allocation to male and female flowers were assessed through measurements of the number and size of flowers of both sexes, and the amount of pollinator visitation. We performed two glasshouse experiments; the first looked at the impact of three levels of pre-flowering herbivory, and the second looked at four levels of herbivory after the plants had started to flower. We found that herbivory during the flowering phase led to a significant increase in the number of plants without male flowers. As a consequence there was significantly less pollen export from this population, as estimated by movement of a pollen analog. The size of female flowers was reduced by severe herbivory, but there was no affect on pollen receipt by the female flowers of damaged plants. The decrease in allocation to male function after severe herbivory may be adaptive when male reproductive success is very unpredictable.     

Corolla herbivory, pollination success and fruit predation in complex flowers: an experimental study with Linaria lilacina (Scrophulariaceae)

BACKGROUND AND AIMS: Herbivory on floral structures has been postulated to influence the evolution of floral traits in some plant species, and may also be an important factor influencing the occurrence and outcome of subsequent biotic interactions related to floral display. In particular, corolla herbivory may affect structures differentially involved in flower selection by pollinators and fruit predators (specifically, those ovopositing in ovaries prior to fruit development); hence floral herbivores may influence the relationships between these mutualistic and antagonistic agents. METHODS: The effects of corolla herbivory in Linaria lilacina (Scrophulariaceae), a plant species with complex flowers, were considered in relation to plant interactions with pollinators and fruit predators. Tests were made as to whether experimentally created differences in flower structure (resembling those occurring naturally) may translate into differences in reproductive output in terms of fruit or seed production. KEY RESULTS: Flowers with modified corollas, particularly those with lower lips removed, were less likely to be selected by pollinators than control flowers, and were less likely to be successfully visited and pollinated. As a consequence, fruit production was also less likely in these modified flowers. However, none of the experimental treatments affected the likelihood of visitation by fruit predators. CONCLUSIONS: Since floral herbivory may affect pollinator visitation rates and reduce seed production, differences among plants in the proportion of flowers affected by herbivory and in the intensity of the damage inflicted on affected flowers may result in different opportunities for reproduction for plants in different seasons.     

Floral herbivory at different stages of flower development changes reproduction in <Emphasis Type="Italic">Iris gracilipes</Emphasis> (Iridaceae)

Floral herbivores and pollinators are major determinants of plant reproduction. Because interaction of floral herbivores and pollinators occurs when herbivores attack the flowers in the bud and flower stages and because the compensatory ability of plants is known to differ according to the timing of herbivory, the effects of herbivory may differ according to its timing. In this study, we investigated the effects of floral herbivory at different stages on fruit production and seed/ovule ratio at two sites of large populations of the perennial herb, Iris gracilipes for 2 years. Herbivory at the bud and fruit stages both tended to have negative effects on fruit production, but the former caused more severe damage. On the other hand, herbivory at the flower stage tended not to have negative effects on fruit production because the degree of flower loss was smaller in the flower stage. Although herbivory decreased fruit production, flowers did not compensate for the damage by increasing the seed/ovule ratio because reproduction of I. gracilipes was limited by pollen availability rather than resources. These results indicate that floral herbivory at different stages has different effects on plant reproduction.     

Assessing the effects of native plants on the pollination of an exotic herb, the blueweed Echium vulgare (Boraginaceae)

The impacts of exotic plants on the pollination and reproductive success of natives have been widely reported; however, in spite of its importance for the invasive process, the role of native plants in the pollination and reproduction of exotic plants has been less explored. To fill this gap, we compared the patterns of pollination and reproductive success in the invasive herb Echium vulgare (Boraginaceae) between monospecific patches (only E. vulgare) and mixed patches (sympatry with native herbs Schizanthus hookeri and Stachys albicaulis) in central Chile. Using sample quadrats of 1 m × 2 m, we quantified the richness, diversity and visitation rate of flower visitors in 15-min observation intervals. We conducted an assay to assess the effect of the patch types (monospecific and mixed) and the isolation of flowers to visitors on both the fruit set and seed/ovule ratio. We showed that native plants favoured the richness of visitors of E. vulgare; however, they did not lead to increases in visitation rate. The reproductive success of E. vulgare did not show differences between contrasted patches; however, the isolation of visitors decreased the fruit set, although seed production was maintained in the absence of pollinators, presumably by an autogamous mechanism. Complementary to our main research focus, we assessed changes in pollination variables and reproductive output in two coflowering native plants that occur with E. vulgare, S. hookeri and S. albicaulis. Despite the fact that our correlational study did not allow us to dissect the effects of mixed patches and relative plant abundances on variables measured for natives, we observed an increase in pollinator richness in mixed patches for the two plants studied. These results suggest a potential facilitation for visitor richness of the exotic plant in coexistence with native plants, although this facilitation does not result in changes in the visit rate or on the reproductive success of any of the studied species. This work underlines the need for additional research on community levels that assess reciprocal effects on pollination between coflowering natives and exotics.     

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.     

Effects of Brachypterolus pulicarius (L.) (Coleoptera: Nitidulidae) on Growth and Seed Production of Dalmatian toadflax,Linaria genistifolia ssp. dalmatica (L.) Maire and Petitmengin (Scrophulariaceae)

The impact of the ovary-feeding beetle Brachypterolus pulicarius on the growth and reproduction of Dalmatian toadflax, Linaria genistifolia spp. dalmatica, was evaluated in greenhouse and field experiments. Studies were conducted with paired plants (with and without B. pulicarius) in the greenhouse and field. Plants from three different age groups (3, 6, and 12 months old) were used. Results of both split-plot analysis of variance and path coefficient analysis indicated that B. pulicarius feeding reduced the height of Dalmatian toadflax plants by up to 23 cm; increased the number of primary and secondary branches by 77 and 95%, respectively; reduced the number of flowers produced per plant by 44 to 49%; and decreased seed production by 43 to 93%. Brachypterolus pulicarius affects reproduction allocation, seed production, and dispersal and may reduce the potential for rapid adaptation by Dalmatian toadflax because fewer seeds will limit the chance of successful mutations. Therefore, B. pulicarius may prove to be an important component in the integrated weed management of Dalmatian toadflax.     

Regional-scale impact of the weed biocontrol agent Mecinus janthinus on Dalmatian toadflax (Linaria dalmatica)

Dalmatian toadflax (Linaria dalmatica (L.) Mill.) is an important invasive plant on rangelands throughout western North America. In 1991, the stem-mining weevil, Mecinus janthinus Germar, was introduced into Canada from Europe as a classical biological control agent to reduce toadflax densities and improve rangelands, particularly in British Columbia. To determine if the program was a success at a regional level, this paper answers three key questions: (1) has M. janthinus spread throughout the study area, (2) is M. janthinus causing a decline in toadflax plant size or density at the regional scale, and (3) has the distribution of toadflax plants changed following M. janthinus introduction? These questions are answered by combining historical survey data and mensurative experimental data on plant and weevil densities across a 40,000 km² area in southern British Columbia. The results show that through a combination of intentional redistribution and natural dispersal weevils have spread throughout the study area. Stem densities at naturally colonized sites and historical release sites were equally low. Across weevil populations between 3 and 10 years old, weevil densities peaked in the eighth year, and there was a negative relationship between weevil density and stem length. Between 2000 and 2007, toadflax patches were found to both decrease in density and become more fragmented over time, with 15% of patches disappearing completely. These findings show that M. janthinus has had a significant negative impact on both the density and distribution of Dalmatian toadflax throughout a large part of its range in British Columbia.     

Twenty‐five years after: post‐introduction association of Mecinus janthinus s.l. with invasive host toadflaxes Linaria vulgaris and Linaria dalmatica in North America

Linaria vulgaris, common or yellow toadflax, and Linaria dalmatica, Dalmatian toadflax (Plantaginaceae), are Eurasian perennial forbs invasive throughout temperate North America. These Linaria species have been the targets of classical biological control programmes in Canada and the USA since the 1960s. The first effective toadflax biological control agent, the stem‐mining weevil Mecinus janthinus (Coleoptera: Curculionidae) was introduced from Europe in the 1990s. This weevil has become established on L. dalmatica and L. vulgaris in both countries, although it has shown greater success in controlling the former toadflax species. Genetic and ecological studies of native range M. janthinus populations revealed that weevils previously identified as a single species in fact include two cryptic species, now recognised as M. janthinus, associated with yellow toadflax, and the recently confirmed species Mecinus janthiniformis, associated with Dalmatian toadflax. The results of a comprehensive study characterising haplotype identities, distributions and frequencies within M. janthinus s.l. native range source populations were compared to those populations currently established in the USA and Canada. The presence of both Mecinus species in North America was confirmed, and revealed with a few exceptions a high and consistent level of host fidelity throughout the adopted and native ranges. Genetic analysis based on mitochondrial cytochrome oxidase subunit II gene (mtCOII) defined the origin and records the subsequent North American establishment, by haplotype, of the European founder populations of M. janthinus (northern Switzerland and southern Germany) and M. janthiniformis (southern Macedonia), and provided population genetic indices for the studied populations. This analysis together with existing North American shipment receipt, release and rearing records elucidates probable redistribution routes and sources of both weevil species from initially released and established adopted range populations.     

Competition and facilitation among plants for pollination: can pollinator abundance shift the plant–plant interactions?

We hypothesize interactions among plants for pollination may depend on pollinator abundance, which always varies among years and habitats and has different effects on plant reproductive success. Honeybee-pollinated plants, Lotus corniculatus, and its commonly coflowering neighbor, Potentilla reptans var. sericophylla, were used in a two-year project. We designed six types of plant combinations with different conspecific and interspecific flower densities in 2011 and repeated this in the same site in 2012. Meanwhile, we artificially increased pollinator abundance by hiring beehives only in 2011. Pollinator abundance as well as flower density significantly affected pollination of L. corniculatus plants from both the conspecific and interspecific plots. Total number of bees visiting a plot was enhanced by an increase in both the conspecific and interspecific flower densities regardless of high or low pollinator abundance. However, changes in visitation rates and fruit sets in the focal plants when flower densities were increased depended on pollinator abundance. Under high pollinator abundance, an increase in both the conspecific and interspecific flower densities significantly enhanced pollinator visits to L. corniculatus. However, under low pollinator abundance, the pollinator visitation rate remained unchanged as conspecific flower density increased, but decreased when there was an increase in interspecific flower density. Coflowering plants enhanced fruit sets of L. corniculatus only when the pollinator abundance was high. The findings suggest that the interactions among plants for pollination are influenced not only by a plant density threshold, but also by a pollinator abundance threshold.     

Herbivore‐induced changes in flower scent and morphology affect the structure of flower–visitor networks but not plant reproduction

Herbivory induces various responses in plants, thus altering the plants’ phenotype in chemical and morphological traits. Herbivore‐induced changes in vegetative plant parts, plant‐physiological mechanisms, and effects on plant‐animal interactions have been intensively studied from species to community level. In contrast, we are just beginning to examine herbivore‐induced effects on reproductive plant parts and flower–visitor interactions, especially in a community context. We investigated the effect of herbivory at different plant developmental stages on plant growth, floral and vegetative phenotype and reproduction in Sinapis arvensis (Brassicaceae). Additionally, we tested how herbivore‐induced plant responses affect flower–visitor interactions and plant reproduction in species‐rich communities. Our results indicate that the timing of herbivory affects the magnitude of changes in plant traits. Herbivory in early but not in late development accelerated the plant's flowering phenology, reduced vegetative growth, increased stem trichome density and altered floral morphology and scent. These findings suggest age‐dependent tradeoffs between growth, defense and reproduction. Herbivore‐induced changes in flower traits also affected flower–visitor interactions in a community context with effects on the structure of flower–visitor networks. However, changes in the network structure had neglectable effects on plant reproduction, i.e. plants were able to compensate altered flower visitor behavior. Thus, herbivory is a source of intraspecific variation in reproductive traits, which can be behaviorally relevant for potential pollinators. However, plants were capable to maintain reproductive success suggesting a tolerance against herbivory. We conclude that in our study system induced direct or indirect defenses that have often been shown to decrease negative effects of herbivores on vegetative plant parts come at no costs for plant reproduction.     

Shading by invasive shrub reduces seed production and pollinator services in a native herb

Plant invasions disrupt native plant reproduction directly via competition for light and other resources and indirectly via competition for pollination. Furthermore, shading by an invasive plant may reduce pollinator visitation and therefore reproduction in native plants. Our study quantifies and identifies mechanisms of these direct and indirect effects of an invasive shrub on pollination and reproductive success of a native herb. We measured pollinator visitation rate, pollen deposition, and female reproductive success in potted arrays of native Geranium maculatum in deciduous forest plots invaded by the non-native shrub Lonicera maackii and in two removal treatments: removal of aboveground L. maackii biomass and removal of flowers. We compared fruit and seed production between open-pollinated and pollen-supplemented plants to test for pollen and light limitation of reproduction. Plots with L. maackii had significantly lower light, pollinator visitation rate, and conspecific pollen deposition to G. maculatum than biomass removal plots. Lonicera maackii flower removal did not increase pollinator visitation or pollen deposition compared to unmanipulated invaded plots, refuting the hypothesis of competition for pollinators. Thus, pollinator-mediated impacts of invasive plants are not limited to periods of co-flowering or pollinator sharing between potential competitors. Geranium maculatum plants produced significantly fewer seeds in plots containing L. maackii than in plant removal plots. Seed set was similar between pollen-supplemented and open-pollinated plants, but pollen-supplemented plants exhibited higher seed set in plant removal plots compared to invaded plots. Therefore, we conclude that the mechanism of impact of L. maackii on G. maculatum reproduction was increased understory shade.     

Effects of above- and belowground herbivory on growth,pollination, and reproduction in cucumber

Plants experience unique challenges due to simultaneous life in two spheres, above- and belowground. Interactions with other organisms on one side of the soil surface may have impacts that extend across this boundary. Although our understanding of plant–herbivore interactions is derived largely from studies of leaf herbivory, belowground root herbivores may affect plant fitness directly or by altering interactions with other organisms, such as pollinators. In this study, we investigated the effects of leaf herbivory, root herbivory, and pollination on plant growth, subsequent leaf herbivory, flower production, pollinator attraction, and reproduction in cucumber (Cucumis sativus). We manipulated leaf and root herbivory with striped cucumber beetle (Acalymma vittatum) adults and larvae, respectively, and manipulated pollination with supplemental pollen. Both enhanced leaf and root herbivory reduced plant growth, and leaf herbivory reduced subsequent leaf damage. Plants with enhanced root herbivory produced 35% fewer female flowers, while leaf herbivory had no effect on flower production. While leaf herbivory reduced the time that honey bees spent probing flowers by 29%, probing times on root-damaged plants were over twice as long as those on control plants. Root herbivory increased pollen limitation for seed production in spite of increased honey bee preference for plants with root damage. Leaf damage and hand-pollination treatments had no effect on fruit production, but plants with enhanced root damage produced 38% fewer fruits that were 25% lighter than those on control plants. Despite the positive effect of belowground damage on honey bee visitation, root herbivory had a stronger negative effect on plant reproduction than leaf herbivory. These results demonstrate that the often-overlooked effects of belowground herbivores may have profound effects on plant performance.     

Floral herbivore effect on the sex expression of an andromonoecious plant,Isomeris arborea (Capparaceae)

Flower-feeding insects may influence the reproductive behavior of their host plant. In plants with labile sex expression, the ratio of maternal to paternal investment may change in response to damage, an effect that goes beyond the direct reduction of plant gametes. We examined the effects of floral herbivory by the beetle Meligethes rufimanus (Nitidulidae) on the ratio of hermaphroditic flowers to male flowers in an andromonoecious shrub, Isomeris arborea (Capparaceae) in southern California. Plants exposed to herbivory had a greater rate of flower bud abortion than those protected from herbivory. Exposed plants produced a greater proportion of hermaphroditic flowers to male flowers, although damaged inflorescences still produced fewer fruit. An additional manipulative experiment showed that the removal of pistils on inflorescences led to an increase in the proportion of hermaphroditic flowers. This suggests that the presence of fruit may lead to pistil suppression in developing flowers. Adaptive responses to herbivory which favor andromonoecy thus include the continued production of hermaphroditic flowers when floral damage is high (and hence low fruit set), and a switch to male flower production when floral damage is low (and fruit production increases). The consequences of an altered six ratio induced by insect herbivores may lead to indirect effects on both the male and female reproductive success of this plant.     

Novel interactions of non-pollinating ants with pollinators and fruit consumers in a tropical forest

The tropical ants Ectatomma ruidum and E. tuberculatum (Formicidae) regularly patrol leaves, flowers, and fruits of the understory shrub, Psychotria limonensis (Rubiaceae), on Barro Colorado Island, Panama. Ant and pollinator exclusion experiments elucidated both positive and negative effects of ant attendance on plant reproductive success, including pollination, fruit set, fruit loss, and fruit removal. Ants did not pollinate flowers but did contribute to higher pollination success, probably by increasing the relocation frequency of winged pollinators and thus the rate of flower visitation. Ants also prevented fruit loss to herbivorous insects which were common during the early stages of fruit development. Thus, ant attendance strongly improved both pollination and fruit set whereby plants with ants set more fruit per flower and also lost fewer fruits during fruit maturation. In contrast, ants had a negative effect on the removal of ripe fruits by avian frugivores. Thus, ant attendance has a non-trivial influence on plant reproduction, this interaction being beneficial at some stages of the plant reproductive cycle and carrying costs at another stage. A tight ecological or co-evolved relationship between these Ectatomma spp. and P. limonensis is unlikely given that ant attendance of plants is detrimental to fruit removal. Received: 18 May 1998 / Accepted: 1 March 1999     

Unpaved roads disrupt the effect of herbivores and pollinators on the reproduction of a dominant shrub

Anthropogenic linear developments, such as trails and firebreaks, also called soft linear developments (SLD), can influence animal behavior, altering the ecological interactions in which animals are involved. For example, SLD can affect the behavior of pollinators and herbivores, but little is known about the combined effect of these three elements on plant reproduction.We evaluated the combined effect of SLD, insect pollinators and herbivores (ungulates) on three reproductive output variables (fruit set, seed set, and seed mass) of a Mediterranean shrub (Halimium halimifolium). We considered two different habitats (SLD verges vs. adjacent scrublands), two scenarios of herbivory (with and without ungulates), and three scenarios of pollinator activity (without pollinators, with manual pollination and with natural pollination).SLD had contrasting effects on H. halimifolium reproduction. In the absence of herbivores, overall fruit set was lower in the verges of SLD than in adjacent scrublands, probably due to lower flower pollination rates. Where herbivores were present, overall fruit set was similar between habitats, because ungulate browsing was lower in SLD verges than in adjacent scrublands. The quantity and weight of seeds per fruit was similar in both habitats, probably because all fertilized flowers received similar amounts of pollen.SLD can alter the interaction among pollinators, herbivores and plants, leading to changes in the reproductive performance of the latter. These changes can have strong negative impacts on endangered plants that rely on fruit and seed production to persist. However, SLD verges could be safe places for plants particularly sensitive to herbivory by ungulates.     

Host-plant preference of Brachypterolus pulicarius, an inadvertently introduced biological control insect of toadflaxes

Brachypterolus pulicarius (L.) (Coleoptera: Kateridae) is an inadvertently introduced biological control agent that can reduce seed set in two North American invasive species, yellow (Linaria vulgaris P. Mill.) (Scrophulariaceae) and Dalmatian toadflax (Linaria genistifolia (L.) P. Mill. ssp. dalmatica). The beetles are more common on yellow toadflax than on Dalmatian toadflax. To understand their distribution on the two host plants, we investigated whether they prefer one host to the other and whether individuals aggregate toward conspecifics. In field and laboratory experiments where beetles were presented with a choice of both toadflax species, B. pulicarius sampled from both host plants preferred yellow toadflax. However, in the laboratory experiment, beetles collected from Dalmatian toadflax showed a weaker preference for yellow toadflax than beetles collected from yellow toadflax. In the field experiment, all beetle populations sampled showed similar preferences. When given a choice between yellow toadflax plants with and without trapped adult B. pulicarius, beetles preferred plants with conspecifics, suggesting aggregation toward beetle pheromones or host‐plant volatiles induced by beetle activity. These results do not support the current practice of redistributing North American B. pulicarius onto Dalmatian toadflax because of their preference for yellow toadflax.     

Nonadditive effects of flower damage and hummingbird pollination on the fecundity of Mimulus luteus

Flower herbivory and pollination have been described as interactive processes that influence each other in their effects on plant reproductive success. Few studies, however, have so far examined their joint effects in natural populations. In this paper we evaluate the influence of flower damage and pollination by the hummingbird Oreotrochilus leucopleurus on the fecundity of the Andean monkey flower Mimulus luteus. We performed a 2×2 factorial experiment, with artificial clipping of lower petals and selective exclusion of the hummingbird as main factors. In spite of the relatively low proportion (27.5%) of the variance in seed production accounted for by the full factorial model, artificial damage and hummingbird exclusion, as well as their interaction, were highly significant, indicating nonadditive effects of factors on plant fecundity. In the presence of hummingbirds, undamaged flowers had a seed production that was 1.7-fold higher than for damaged flowers, suggesting that the effect of flower damage on female reproductive success occurs probably as a consequence of hummingbird discrimination against damaged corollas. This result indicates that the impact of flower herbivory on plant fecundity was contingent on the presence or absence of hummingbirds, suggesting that pollinators may indirectly select for undamaged and probably resistant flower phenotypes. A second interaction effect revealed that undamaged flowers produced 78.5% more seeds in the absence of rather than in the presence of O. leucopleurus, raising the question of the ecological mechanism involved. We suggest that the strong territorial behavior exhibited by the bee Centris nigerrima may confine the foraging activities of the remaining bee species to safe sites within exclosures. Overall, our results provide evidence that hummingbird pollination and flower herbivory have interdependent effects on M. luteus fecundity, which indicates that it will be difficult to predict their ecological and evolutionary consequences unless interactions are analyzed in an integrated form.     

Effects of floral herbivory on foraging behaviour of bumblebees and female reproductive success in Pedicularis gruina (Orobanchaceae)

The effects of floral herbivores on floral traits may result in alterations in pollinator foraging behaviour and subsequently influence plant reproductive success. Fed-upon plants may have evolved mechanisms to compensate for herbivore-related decreased fecundity. We conducted a series of field experiments to determine the relative contribution of floral herbivores and pollinators to female reproductive success in an alpine herb, Pedicularis gruina, in two natural populations over two consecutive years. Experimental manipulations included bagging, hand supplemental, geitonogamous pollination, and simulated floral herbivory. Bumblebees not only avoided damaged flowers and plants but also decreased successive visits of flowers in damaged plants, and the latter may reduce the level of geitonogamy. Although seed set per fruit within damaged plants was higher than that in intact plants, total seed number in damaged plants was less than that in intact plants, since floral herbivory-mediated pollinator limitation led to a sharp reduction of fruit set. Overall, the results suggest that resource reallocation within inflorescences of damaged plants may partially compensate for a reduction in seed production. Additionally, a novel finding was the decrease in successive within-plant bumblebee visits following floral herbivory. This may increase seed quantity and quality of P. gruina since self-compatible species exhibit inbreeding depression. The patterns of compensation of herbivory and its consequences reported in this study give an insight into the combined effects of interactions between floral herbivory and pollination on plant reproductive fitness.     

Nectar production,reproductive success and the evolution of generalised pollination within a specialised pollen-rewarding plant family: a case study using <Emphasis Type="Italic">Miconia theizans</Emphasis>

Generalist plant–pollinator interactions are prevalent in nature. Here, we untangle the role of nectar production in the visitation and pollen release/deposition in Miconia theizans, a nectar-rewarding plant within the specialised pollen-rewarding plant family Melastomataceae. We described the visitation rate, nectar dynamics and pollen release from the poricidal anthers and deposition onto stigmas during flower anthesis. Afterwards, we used a linear mixed model selection approach to understand the relationship between pollen and nectar availability and insect visitation rate and the relationship between visitation rate and reproductive success. Miconia theizans was visited by 86 insect species, including buzzing and non-buzzing bees, wasps, flies, hoverflies, ants, beetles, hemipterans, cockroaches and butterflies. The nectar produced explained the visitation rate, and the pollen release from the anthers was best explained by the visitation rate of pollinivorous species. However, the visitation rates could not predict pollen deposition onto stigmas. Nectar production may explain the high insect diversity and led to an increase in reproductive success, even with unpredictable pollen deposition, indicating the adaptive value of a generalised pollination system.