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Interaction webs, or networks, define how the members of two or more trophic levels interact. However, the traits that mediate network structure have not been widely investigated. Generally, the mechanism that determines plant-pollinator partnerships is thought to involve the matching of a suite of species traits (such as abundance, phenology, morphology) between trophic levels. These traits are often unknown or hard to measure, but may reflect phylogenetic history. We asked whether morphological traits or phylogenetic history were more important in mediating network structure in mutualistic plant-pollinator interaction networks from Western Canada. At the plant species level, sexual system, growth form, and flower symmetry were the most important traits. For example, species with radially symmetrical flowers had more connections within their modules (a subset of species that interact more among one another than outside of the module) than species with bilaterally symmetrical flowers. At the pollinator species level, social species had more connections within and among modules. In addition, larger pollinators tended to be more specialized. As traits mediate interactions and have a phylogenetic signal, we found that phylogenetically close species tend to interact with a similar set of species. At the network level, patterns were weak, but we found increasing functional trait and phylogenetic diversity of plants associated with increased weighted nestedness. These results provide evidence that both specific traits and phylogenetic history can contribute to the nature of mutualistic interactions within networks, but they explain less variation between networks.

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 [...]

Pollination syndromes refer to stereotyped floral characteristics (flower colour, shape, etc.) that are associated with a functional group of pollinators (bee, bird, etc.).The trumpet creeper Campsis radicans, endemic to the southeast and mid‐west United States, has been assigned to the hummingbird‐pollination syndrome, due mainly to its red, trumpet‐shaped flowers.Previous studies demonstrated that the ruby‐throated hummingbird Archilochus colubris is C. radicans' primary pollinator, but anecdotal data suggest various bee species may provide pollination service when hummingbirds are absent.This study characterised C. radicans nectar volume and concentration by time of day. Nectar volume was suitable for hummingbirds, but concentration was higher than typical hummingbird‐pollinated plants (∼20% w/w); at ∼30% w/w, it approached the concentration expected in bee‐pollinated plants (∼50% w/w). We also found substantial amounts of nectar at night.Two C. radicans populations received virtually no hummingbird visits, but the number of bees were markedly higher than in the populations previously described. Interestingly, there were no night‐time visitors despite the large quantity of nocturnal nectar.Based on previously published pollen delivery per visit by various species, this study estimated that cumulative deposition by bees routinely reached pollen deposition thresholds for setting fruit in C. radicans. They are, unequivocally, the predominant pollinators in these populations, thus providing pollination service in the absence of hummingbirds.These results highlight C. radicans as a food source for native bees and add to the understanding of how floral phenotypes can facilitate pollination by disparate functional groups. [ABSTRACT FROM AUTHOR]

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.

Extinction through hybridization can threaten endangered species when hybrids are vigorous and fertile. We studied hybridization between the endangered small white lady’s slipper (Cypripedium candidum Muhlenberg ex Willdenow) and the common yellow lady’s slipper (Cypripedium parviflorum Salisbury var. makasin (Farwell) Sheviak and C. parviflorum var. pubescens (Willdenow) O.W. Knight) in four Manitoban populations. We used 8 morphological characters and 1061 amplified fragment length polymorphism (AFLP) loci to characterize variation in 182 plants. Canonical correlation analysis indicated that morphology was highly predictive of genetic composition. Ordination analyses of morphological and genetic data, and Bayesian clustering analysis of the genetic data, all clearly distinguished the two parental species. The two varieties of C. parviflorum were morphologically divergent but occupied the same genetic cluster in both ordination and Bayesian analyses. Putative hybrids had considerable morphological overlap with parental species but were mostly genetically intermediate. Five of 79 individuals assigned to C. candidum and 15 of 71 individuals assigned to C. parviflorum had genetic profiles consistent with mixed ancestry. These results suggest that some introgression has occurred, but genetic assimilation of endangered C. candidum by the more common C. parviflorum does not seem imminent. The high local abundance of C. candidum may reduce its susceptibility to gene flow from C. parviflorum. [ABSTRACT FROM AUTHOR]

Premise of the study : Microsatellite markers were isolated in Polemonium brandegei and P. viscosum to be used in future studies of mating system evolution, population structure, and hybridization. • Methods and Results : Six loci were used in a preliminary genetic diversity study in two populations each of the closely related Polemonium brandegei and P. viscosum . We found 39 alleles across the six loci (average 7 per locus), with overall levels of observed heterozygosities ranging from 0.067 to 0.867 in P. brandegei and 0.000 to 0.666 in P. viscosum . Additional primers are reported, but require further design and optimization. • Conclusions : The reported markers will aid in further studies of mating system evolution, population structure, and hybridization in P. brandegei and P. viscosum . [ABSTRACT FROM AUTHOR]