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Lythrum salicaria is an invasive plant in North America. The study is focused on carbohydrate reserves (especially starch) in below-ground plant organs of the named species. These energy sources are considered as possible contributors of invasive behaviour both in short and long time periods. Another question is whether these storages can be influenced by other factors. These ideas were tested in common garden experiments.

Herbivory can have many effects on plant fitness, including altering plant-pollinator interactions and sexual reproduction in angiosperms. Pollinator-mediated interactions may be impacted when herbivores alter plant traits, such as floral display size, that can influence pollinator visitation rates, and, ultimately, the reproductive component of plant fitness. Here I describe an investigation into the indirect effects of feeding by beetles released as a biological control agent, Galerucella calmariensis and G. pusilla, on plant-pollinator interactions and reproductive output in the invasive plant Lythrum salicaria L. (purple loosestrife). During the summer of 2011, three treatments (low, ambient and mechanical herbivory) were applied to 105 plants during the pre-flowering period of growth. At the onset of flowering, a series of pollinator observations were conducted over the course of approximately 1.5 weeks. Several aspects of floral display were affected by the herbivory treatments, including increased inflorescence and flower production in the ambient and mechanical herbivory treatments, relative to the low herbivory treatment. Treatment type did not have a significant effect on the number of pollinator foraging bouts, but had marginally significant effects on the number of flowers probed per pollinator foraging bout and per 30-minutes. Moreover, treatment had a significant effect on the number of switches among the inflorescences on a single plant. I discuss the possibility that the differences in pollinator visitation were mediated by differences in the architecture and the size of floral display. There were no detectable differences in fruit or seed production (i.e., female fitness) among treatments. However, as I discuss, differences in pollinator visitation may affect other unmeasured aspects of fitness, such as the level of inbreeding or the number of seeds sired through male function.

Biological invasions provide opportunities to study evolutionary processes occurring during contemporary time scales. Here, I combine a literature review of common garden studies of invasive plant species, with field and glasshouse experiments on populations of the outcrossing, perennial, wetland invader Lythrum salicaria (purple loosestrife - Lythraceae), to investigate the evolutionary genetics of local adaptation in reproductive and life-history traits. A review of 32 common garden studies of 28 introduced species identified previously unrecognized latitudinal clines in phenotypic traits in both native and introduced populations. To obtain direct evidence for clinal variation and local adaptation, I investigated populations of L. salicaria sampled along a latitudinal gradient of growing season length in eastern North America. Controlled pollinations of plants from 12 populations provided no evidence for the breakdown of self-incompatibility to self-compatibility towards the northern range limit. However, a quantitative genetic experiment involving 20 populations revealed latitudinal clines in population mean, variance and skew for days to flower and vegetative size. Broad-sense estimates of genetic variance were significant for most traits; however, strong inter-correlations among traits suggested that fitness trade-offs have constrained population divergence. The observed clines supported a model of selection for early flowering in northern populations constrained by a trade-off between age and size at flowering. A comparison of variance-covariance matrices of family and population means (G and D, respectively) of life-history traits demonstrated that populations have evolved in response to selection under genetic constraints, rather than through neutral processes. A reciprocal transplant experiment involving six populations and three common gardens spanning the latitudinal range provided direct evidence for local adaptation in flowering phenology. Populations maintained the same rank-order for time to flowering and vegetative size at each site, and southern populations had the highest fecundity at the southern site but the lowest at the northern site. Finally, a phenotypic selection analysis in each common garden involving 61 F2 families of crosses between a northern × southern populations confirmed that selection favours earlier flowering in northern populations. These results demonstrate that natural selection on reproductive phenology has accompanied the invasive spread of L. salicaria in eastern N. America.

Biological invasions provide opportunities to study evolutionary processes occurring during contemporary time scales. Here, I combine a literature review of common garden studies of invasive plant species, with field and glasshouse experiments on populations of the outcrossing, perennial, wetland invader Lythrum salicaria (purple loosestrife - Lythraceae), to investigate the evolutionary genetics of local adaptation in reproductive and life-history traits. A review of 32 common garden studies of 28 introduced species identified previously unrecognized latitudinal clines in phenotypic traits in both native and introduced populations. To obtain direct evidence for clinal variation and local adaptation, I investigated populations of L. salicaria sampled along a latitudinal gradient of growing season length in eastern North America. Controlled pollinations of plants from 12 populations provided no evidence for the breakdown of self-incompatibility to self-compatibility towards the northern range limit. However, a quantitative genetic experiment involving 20 populations revealed latitudinal clines in population mean, variance and skew for days to flower and vegetative size. Broad-sense estimates of genetic variance were significant for most traits; however, strong inter-correlations among traits suggested that fitness trade-offs have constrained population divergence. The observed clines supported a model of selection for early flowering in northern populations constrained by a trade-off between age and size at flowering. A comparison of variance-covariance matrices of family and population means (G and D, respectively) of life-history traits demonstrated that populations have evolved in response to selection under genetic constraints, rather than through neutral processes. A reciprocal transplant experiment involving six populations and three common gardens spanning the latitudinal range provided direct evidence for local adaptation in flowering phenology. Populations maintained the same rank-order for time to flowering and vegetative size at each site, and southern populations had the highest fecundity at the southern site but the lowest at the northern site. Finally, a phenotypic selection analysis in each common garden involving 61 F2 families of crosses between a northern × southern populations confirmed that selection favours earlier flowering in northern populations. These results demonstrate that natural selection on reproductive phenology has accompanied the invasive spread of L. salicaria in eastern N. America.

Herbivory can have many effects on plant fitness, including altering plant-pollinator interactions and sexual reproduction in angiosperms. Pollinator-mediated interactions may be impacted when herbivores alter plant traits, such as floral display size, that can influence pollinator visitation rates, and, ultimately, the reproductive component of plant fitness. Here I describe an investigation into the indirect effects of feeding by beetles released as a biological control agent, Galerucella calmariensis and G. pusilla, on plant-pollinator interactions and reproductive output in the invasive plant Lythrum salicaria L. (purple loosestrife). During the summer of 2011, three treatments (low, ambient and mechanical herbivory) were applied to 105 plants during the pre-flowering period of growth. At the onset of flowering, a series of pollinator observations were conducted over the course of approximately 1.5 weeks. Several aspects of floral display were affected by the herbivory treatments, including increased inflorescence and flower production in the ambient and mechanical herbivory treatments, relative to the low herbivory treatment. Treatment type did not have a significant effect on the number of pollinator foraging bouts, but had marginally significant effects on the number of flowers probed per pollinator foraging bout and per 30-minutes. Moreover, treatment had a significant effect on the number of switches among the inflorescences on a single plant. I discuss the possibility that the differences in pollinator visitation were mediated by differences in the architecture and the size of floral display. There were no detectable differences in fruit or seed production (i.e., female fitness) among treatments. However, as I discuss, differences in pollinator visitation may affect other unmeasured aspects of fitness, such as the level of inbreeding or the number of seeds sired through male function.

Herbivory can have many effects on plant fitness, including altering plant-pollinator interactions and sexual reproduction in angiosperms. Pollinator-mediated interactions may be impacted when herbivores alter plant traits, such as floral display size, that can influence pollinator visitation rates, and, ultimately, the reproductive component of plant fitness. Here I describe an investigation into the indirect effects of feeding by beetles released as a biological control agent, Galerucella calmariensis and G. pusilla, on plant-pollinator interactions and reproductive output in the invasive plant Lythrum salicaria L. (purple loosestrife). During the summer of 2011, three treatments (low, ambient and mechanical herbivory) were applied to 105 plants during the pre-flowering period of growth. At the onset of flowering, a series of pollinator observations were conducted over the course of approximately 1.5 weeks. Several aspects of floral display were affected by the herbivory treatments, including increased inflorescence and flower production in the ambient and mechanical herbivory treatments, relative to the low herbivory treatment. Treatment type did not have a significant effect on the number of pollinator foraging bouts, but had marginally significant effects on the number of flowers probed per pollinator foraging bout and per 30-minutes. Moreover, treatment had a significant effect on the number of switches among the inflorescences on a single plant. I discuss the possibility that the differences in pollinator visitation were mediated by differences in the architecture and the size of floral display. There were no detectable differences in fruit or seed production (i.e., female fitness) among treatments. However, as I discuss, differences in pollinator visitation may affect other unmeasured aspects of fitness, such as the level of inbreeding or the number of seeds sired through male function.

The release of biological control agents into the environment is inherently risky: assessment of those risks through on-going, post-release monitoring is very important. Herbivores have the potential to inflict multiple impacts on a host plant’s performance and reproduction. Previous research demonstrates that the effects of herbivory on plants include changes to plant architecture, biomass allocation, flowering time and reproductive success, to list a few. Moreover, when herbivory significantly impacts the population ecology of a dominant community member, other species can be indirectly affected, ultimately influencing plant community ecology. Here I describe an investigation into the impacts of two introduced herbivorous biological control agents: the leaf beetle Galerucella calmariensis (Coleoptera: Chrysomelidae), and the flower-feeding weevil, Nanophyes marmoratus (Coleoptera: Brentidae) on several characteristics of the host plant species, invasive purple loosestrife (Lythrum salicaria), and its surrounding community. I collected data on 18 invaded communities from around eastern Ontario, including information on feeding damage and the density of each species of biological control, along with data on purple loosestrife’s height and biomass, inflorescence length, inflorescence number and fruit production. The history of each site’s colonization by Galerucella was also considered. I discovered that the density of both Galerucella and Nanophyes at a site was negatively associated with Lythrum fruit production. However, herbivore density was not significantly associated with Lythrum biomass, height or the species richness of the surrounding plant community. This study, conducted 20 years after the initial Ontario release of Galerucella, demonstrates that although vegetative traits of Lythrum do not appear to be significantly impacted by the presence of Galerucella or Nanophyes, reproductive traits are. Twenty years is likely too short a time period to adequately assess the impacts of the release on community species richness, although my data indicate that communities with smaller Lythrum plants tend to have higher species richness. This study covered a small geographical area and data collection was conducted for a single season only; adding additional years and/ or sites is recommended.

<p>I combined comparative and experimental studies in the field and in the greenhouse to examine factors influencing reproductive success in two insect-pollinated herbs, the tristylous, selfincompatible perennial <i>Lythrum salicaria</i> and the self-compatible, biennial <i>Pedicularis palustris</i>. More specifically, I explored (i) the effects of plant population characteristics on the intensity and outcome of interactions with pollinators and seed predators, (ii) whether flower morphology affects duration of stigma receptivity, and (iii) whether damage-induced reduction in floral display reduces pollinator visitation and increases pollen limitation.</p><p>As predicted, the rate of pollinator visitation tended to increase and the number of flowers probed per plant tended to decrease with increasing population size in <i>L. salicaria</i>, but these relationships only approached statistical significance. By taking advantage of the pollen size polymorphism that is typical of many heterostylous plants, I could show that the number of compatible pollen grains received increased with population size, and that this was associated with a reduction in pollen limitation and increased seed output per flower. The deposition of high numbers of incompatible conspecific and heterospecific pollen grains did not appear to reduce seed set.</p><p>In <i>P. palustris</i>, fruit set and seed predation varied markedly among populations and years, but this variation could only partly be explained by variation in population size. Fruit set was positively related to population size, and seed predation was negatively related to population size, in one of three years. Similarly, the level of pollen limitation, which was quantified in two years, varied among populations, but was not related to population size, density or isolation.</p><p>In <i>L. salicaria</i>, both the duration of stigma receptivity and the effect of prior self-pollination on seed output varied among style morphs. These differences may contribute to morph-specific differences in pollen limitation and seed production documented in the field.</p><p>The results of a field experiment demonstrated that damage to the shoot apex may markedly reduce fruit production in <i>L. salicaria</i>, and suggested that this is mainly because damage reduces flower number. I found no evidence that a reduced floral display increased the severity of pollen limitation.</p><p>Taken together, the results show that interactions with both pollinators and herbivores may markedly affect reproductive output in the two plant species, and that the intensity of both mutualistic and antagonistic interactions vary considerably in space and time. Moreover, they are consistent with the hypothesis that pollination success should depend less on population size in selfcompatible than in self-incompatible plants.</p>

I combined comparative and experimental studies in the field and in the greenhouse to examine factors influencing reproductive success in two insect-pollinated herbs, the tristylous, selfincompatible perennial Lythrum salicaria and the self-compatible, biennial Pedicularis palustris. More specifically, I explored (i) the effects of plant population characteristics on the intensity and outcome of interactions with pollinators and seed predators, (ii) whether flower morphology affects duration of stigma receptivity, and (iii) whether damage-induced reduction in floral display reduces pollinator visitation and increases pollen limitation. As predicted, the rate of pollinator visitation tended to increase and the number of flowers probed per plant tended to decrease with increasing population size in L. salicaria, but these relationships only approached statistical significance. By taking advantage of the pollen size polymorphism that is typical of many heterostylous plants, I could show that the number of compatible pollen grains received increased with population size, and that this was associated with a reduction in pollen limitation and increased seed output per flower. The deposition of high numbers of incompatible conspecific and heterospecific pollen grains did not appear to reduce seed set. In P. palustris, fruit set and seed predation varied markedly among populations and years, but this variation could only partly be explained by variation in population size. Fruit set was positively related to population size, and seed predation was negatively related to population size, in one of three years. Similarly, the level of pollen limitation, which was quantified in two years, varied among populations, but was not related to population size, density or isolation. In L. salicaria, both the duration of stigma receptivity and the effect of prior self-pollination on seed output varied among style morphs. These differences may contribute to morph-specific differences in pollen limitation and seed production documented in the field. The results of a field experiment demonstrated that damage to the shoot apex may markedly reduce fruit production in L. salicaria, and suggested that this is mainly because damage reduces flower number. I found no evidence that a reduced floral display increased the severity of pollen limitation. Taken together, the results show that interactions with both pollinators and herbivores may markedly affect reproductive output in the two plant species, and that the intensity of both mutualistic and antagonistic interactions vary considerably in space and time. Moreover, they are consistent with the hypothesis that pollination success should depend less on population size in selfcompatible than in self-incompatible plants.