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Recent work on the ecosystem service of biodiversity suggests that higher pollinator diversity could lower pollen limitation, but these two aspects of plant-pollinator communities have only rarely been causally connected. Here we present a review of studies that produced quantitative assessments of both pollinator diversity and evenness as well as pollen limitation of focal plant species. Although pollen limitation is expected to be lower when pollinator diversity is high, our analysis suggests this relationship is weak. The relationship may be obscured when features of the plant species (e.g., average level of specialization) are confounded with features of the plant communities (e.g., habitat). We encourage researchers investigating pollen limitation to consider including measures of diversity of the floral visitors, and their effectiveness. These data would permit a more powerful test of the relationships among these variables and improve our understanding of the critical elements of stable plant-pollinator networks. Key words: ecosystem services, pollination, pollen, insects, flowering plants, pollinator diversity. Un travail recent sur les services rendus aux ecosystemes par la biodiversite suggere qu'une plus grande diversite de pollinisateurs pourrait reduire la limitation par le pollen, mais on a rarement etabli la relation de cause a effet de ces deux aspects de la relation plantes-pollinisateurs communautes. Les auteurs presentent une revue des etudes ayant produit des evaluations quantitatives a la fois de la diversite des pollinisateurs et l'uniformite et de la limitation par le pollen d'especes vegetales determinees. Bien que l'on s'attende a ce que la limitation par le pollen soit plus faible en presence d' une forte diversite de pollinisateurs, les auteurs constatent que cette relation est faible. La relation est possiblement masquee lorsque les particularites de l'espece vegetale (p. ex., degre moyen de specialisation) se confondent avec les particularites des communautes vegetales (p. ex., habitat). On encourage les chercheurs sur la limitation par le pollen a considerer des mesures inclusives de la diversite des visiteurs floraux, et leur efficacite. Ces donnees fourniraient une evaluation plus forte des relations entre ces variables et amelioreraient notre comprehension des elements critiques des reseaux stables plante-pollinisateur. Mots-cles : services aux ecosystemes, pollinisation, pollen, insectes, plantes a fleurs, diversite des pollinisateurs. [Traduit par la Redaction], Introduction Pollen limitation (PL), the reduction in plant reproductive success as a result of inadequate quantity or quality of pollen deposition, is widespread among flowering plants. Previous reviews have calculated [...]

Species with limited geographic ranges are often of conservation concern because they may possess low levels of genetic variability and thus have a reduced ability to respond to stochastic events. As a consequence, an important conservation strategy is to maximize a species' adaptive potential by preserving natural levels of genetic variation. With this goal in mind, we assessed genetic variation within and among six populations of the Ouachita Mountain endemic Carex latebracteata Waterfall using 653 amplified fragment length polymorphism (AFLP) loci. Indices of genetic variation [% polymorphic loci, expected heterozygosity ([H.sub.E]), population differentiation ([Φ.sub.PT])] were most consistent with an outcrossing or mixed mating system despite an inflorescence morphology that seems conducive to self-pollination. An analysis of molecular variance (AMOVA) showed that >80% of the variation occurred within populations, suggesting high levels of gene flow. The close geographic proximity of most populations, which are often adjacent to streams, may facilitate long-distance seed dispersal and help to maintain high infra-population genetic variation. Conservation strategies focused on maintaining the ecological integrity of rivers and streams, and the provision of naturally vegetated buffers would likely assist in the conservation of this and other Ouachita Mountain endemics. Key words: Carex, Cyperaceae, conservation, genetic variation, AFLPs, Ouachita Mountains. Les especes avec des distributions geographiques limitees font souvent 1'objet de preoccupation de conservation peut-etre parte qu'elles possedent une faible variability genetique et ainsi manifestent une moindre capacite a reagir a des evenements stochastiques. Consequemment, la conservation de degres eleves de variation genetique constitue une importante strategie de conservation pour maximiser le potential d'adaptation de 1'espece. Avec cet objectif, les auteurs ont evalue la variation genetique dans et entre six populations dune plante endemique de Ouachita Mountain, le Carex latebracteata Waterfall, en utilisant le polymorphisme des fragments amplifies (AFLP) de 653 lieux. L'indice de variation genetique [% lieux polymorphiques, heterozygocite attendue ([H.sub.E]), differentiation des populations ([Φ.sub.pt])] correspond mieux avec des systemes d'heterocroisement ou de croisement melanges, en depit dune morphologie de l'inflorescence qui semble conduire a 1'autofecondation. Une analyse de la variance moleculaire (AMOVA) montre que >80 % de la variation se retrouve dans les populations, ce qui suggere de hauts degres de flux genetique. L'etroite proximity geographique de la plupart des populations, souvent adjacentes a des ruisseaux, peut cider la dispersion sur de longues distances pour ainsi maintenir une forte variation genetique intrapopulation. Des strategies de conservation visant a maintenir 1'integrite ecologique des ruisseaux et des rivieres, et le maintain de zones tampons en vegetation naturally pourront vraisemblablement cider la conservation de cette endemique et autres, de Ouachita Mountain. Mots-cles : Carex, Cyperacees, conservation, variation genetique, AFLPs, Ouachita Mountains. [Traduit par la Redaction], Introduction Species with limited geographic ranges are frequently of conservation concern because they may be less variable genetically than more widely distributed taxa (Karron 1987; Hamrick and Godt 1990). As [...]

Research has been conducted on the effect of the flower size and number trade-offs on the floral display evolution. Results indicate that the short-term evolution of the floral display is not constrained by trade-offs between the flower size and number.

1 Sexual reproduction, vegetative propagation and growth of Pinguicula vulgaris were monitored at two sites in Alberta, Canada during a single growing season. Seed number, biomass invested in growth, and vegetative propagation (gemmae production) were used as indices of resource allocation. Allocations to sexual reproduction, vegetative propagation and growth were analysed relative to allocation to the other two functions, plant size (winter bud mass), and site. 2 The effects of plant size on patterns of resource investment were not consistent. Allocation to growth varied negatively with plant size, particularly in large fruiting plants. In contrast, sexual reproduction and gemmae production varied positively with plant size: seed and fruit production increased allometrically, whereas allocation to gemmae was isometric. 3 In isolation from the effects of plant size, trade-offs occurred between sexual reproduction and vegetative functions (growth and gemmae production), whereas vegetative propagation and growth varied positively. Decreased gemmae production by fruiting plants, even after the effects of reproduction on growth had been accounted for, implied that: (1) reproduction affected vegetative propagation and growth independently; (2) growth was favoured over vegetative propagation; and (3) reproduction was more costly than indicated by simple trade-offs. Positive relations between growth and vegetative propagation probably arise because gemmae are in effect axillary buds on the over-wintering structure. 4 These allocation patterns, combined with threshold sizes for reproduction, suggest an emphasis on growth until a minimum size is reached. Beyond this threshold, resources not required to maintain size seem to be allocated to current reproduction. We suggest that resource allocation by P. vulgaris may reflect growth form and phenology as well as the relative probabilities of adult, gemmae and seedling survival. Plants of similar growth form and/or phenology, such as bulb- or corm-forming species, probably employ similar strategies of resource allocation. Keywords: growth, plant size, seed production, trade-offs, vegetative propagation

Floral displays advertise rewards to potential pollinators and vary strikingly in the size, number and arrangement of flowers. Pollinators generally prefer both more and larger flowers. However, finite floral resources mean that trade-offs should occur between flower size and flower number. The evolution of floral display depends on the heritability of floral traits as well as how floral allocation affects fitness. We examined phenotypic and genetic components of floral display in bee-pollinated Eichhornia paniculata. Previous studies have revealed among-population differentiation as well as considerable plasticity for inflorescence and floral traits. We grew open pollinated seed from two Brazilian populations. Flower number, flower size, age at flowering, and the area of the bract subtending the inflorescence (an index of resource availability) were measured on the first two inflorescences of 6 plants/family and 60 maternal families/population (720 plants in total). Both flower size and number varied positively with all indices of resource levels, i.e. bract area, age at flowering, and developmental stage (inflorescence 1 or 2), confirming that resource status affects floral display. At a given resource level, daily flower production varied negatively with daily flower size indicating that floral trade-offs may occur at a very fine temporal scale. Mean broad-sense heritability was 16 % for flower size and 10 % for flower number, although these estimates varied between populations and inflorescences.

When resource availability changes frequently and unpredictably, natural selection favors flexible resource allocation; however, such versatility may be compromised in perennial plants that differentiate leaves or flowers a year in advance of their development (preformation). We investigated resource allocation by the carnivorous perennial Pinguicula vulgaris to determine whether increased resource availability changes within-season allocation to growth, vegetative propagation, and reproduction. In response to resource supplementation (feeding with fruit flies), plants attained a mass 60% greater than that of unfed plants after a single growing season. Feeding also enhanced vegetative propagation, which is closely associated with growth, without modifying relations between these two vegetative functions. In contrast, feeding did not alter the size of vegetative rosettes or the within-season incidence of either flowering or fruiting. This lack of immediate responses occurred because floral and leaf primordia differentiated up to 10 mo before resource supplementation and flower development. However, enhanced resource status likely affected future reproduction indirectly through resource effects on plant size. Large plants produced more floral primordia and between-year changes in fruiting status corresponded to changes in plant size. These results illustrate that preformation can delay responses to enhanced resources by perennial plants. Key words: growth; Lentibulariaceae; Pinguicula vulgaris; preformation; reproduction; supplemental resources; tradeoffs; vegetative propagation.