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A growing body of work indicates that the timing of flowering of temperate angiosperms has been affected by shifts in climate since the 1970s. Sensitivity in flowering phenology to changing temperatures has been particularly well-documented, but widespread phenological sensitivity to changing precipitation patterns in temperate communities has only been shown in a few studies. The exception is relationships between snowpack and early flowering in alpine environments, whereby the timing of flowering herbs had strong associations with winter precipitation and the snowmelt timing. Based on these results, we hypothesized that populations in temperate latitudes characterized by strong seasonality and winter snowfall would demonstrate associations between timing of snowmelt and flowering phenology. We combined a historical dataset of first flowering dates in a Minnesota tallgrass prairie with climatic data to construct a structural equation model, testing hypotheses on the relationships between winter precipitation, temperature, and flowering phenology. While temperature had a strong effect on flowering phenology, winter precipitation had a significant relationship with only a few species. The species affected by snow were later flowering species, which is inconsistent with our prediction that winter precipitation affects early flowering phenology. These results suggest future changes in precipitation will have differing consequences depending on region. Key words: phenology, snow, structural equation modeling, prairie, plants, flowering, historical data. De plus en plus de travaux indiquent que la période de floraison des angiospermes tempérées est affectée par les changements climatiques survenus depuis les années 1970. La sensibilité de la phénologie de la floraison aux changements de températures a été particulièrement bien documentée, mais une sensibilité phénologique étendue aux changements des régimes de précipitations dans les communautés tempérées n'a été démontrée que dans quelques études. L'exception concerne les relations entre le manteau neigeux et la floraison précoce dans les environnements alpins, où le moment de la floraison des herbes présente de fortes associations avec les précipitations hivernales et le moment de la fonte des neiges. Sur la base de ces résultats, les auteurs ont émis l'hypothèse que les populations des latitudes tempérées, caractérisées par une forte saisonnalité et des chutes de neige hivernales, montreraient des associations entre le moment de la fonte des neiges et la phénologie de la floraison. Ils ont combiné un ensemble de données historiques sur les dates de première floraison dans la prairie à herbes hautes du Minnesota avec des données climatiques pour construire un modèle d'équation structurelle, testant les hypothèses sur les relations entre les précipitations hivernales, la température et la phénologie de la floraison. Alors que la température avait un effet important sur la phénologie de la floraison, les précipitations hivernales n'avaient une relation significative qu'avec quelques espèces. Les espèces affectées par la neige étaient des espèces à floraison tardive, ce qui est incompatible avec leur prédiction selon laquelle les précipitations hivernales affectent la phénologie de floraison précoce. Ces résultats suggèrent que les changements futurs dans les précipitations auront des conséquences différentes selon les régions. [Traduit par la Rédaction] Mots-clés : phénologie, neige, modèle d'équation structurelle, prairie, plantes, floraison, données historiques., Introduction One of the most well-documented biotic effects of climate change is changing flowering phenology or flower timing (Parmesan 2006; Schwartz et al. 2006; Cleland et al. 2007; Miller-Rushing and [...]

Phenological events - defined points in the life cycle of a plant or animal - have been regarded as highly plastic traits, reflecting flexible responses to various environmental cues. The ability of a species to track, via shifts in phenological events, the abiotic environment through time might dictate its vulnerability to future climate change. Understanding the predictors and drivers of phenological change is therefore critical. Here, we evaluated evidence for phylogenetic conservatism - the tendency for closely related species to share similar ecological and biological attributes - in phenological traits across flowering plants. We aggregated published and unpublished data on timing of first flower and first leaf, encompassing ̃4000 species at 23 sites across the Northern Hemisphere. We reconstructed the phylogeny for the set of included species, first, using the software program Phylomatic, and second, from DNA data. We then quantified phylogenetic conservatism in plant phenology within and across sites. We show that more closely related species tend to flower and leaf at similar times. By contrasting mean flowering times within and across sites, however, we illustrate that it is not the time of year that is conserved, but rather the phenological responses to a common set of abiotic cues. Our findings suggest that species cannot be treated as statistically independent when modelling phenological responses. Synthesis. Closely related species tend to resemble each other in the timing of their life-history events, a likely product of evolutionarily conserved responses to environmental cues. The search for the underlying drivers of phenology must therefore account for species' shared evolutionary histories. Closely related species tend to resemble each other in the timing of their life-history events, a likely product of evolutionarily conserved responses to environmental cues. The search for the underlying drivers of phenology must therefore account for species' shared evolutionary histories. © 2013 British Ecological Society.

An important consequence of self-compatibility in plants is that self-pollination can have deleterious effects on plantfitness because of inbreeding. We conducted a hand pollination experiment under field conditions to measure the magnitude of inbreeding depression associated with self-pollination in the rare western prairie fringed-orchid Platanthera praeclara Sheviak and Bowles. By comparing capsules and seeds resulting from cross versus self-pollination treatments, we determined that self-pollination reduces seed quality while having no detectable effect on capsule production or seed numbers. A smaller percentage of seeds resulting from self-pollination contained an embryo (18%) relative to seeds from cross-pollination (46%). Seeds that had an embryo were scored for the size of the embryo, small or large. A smaller proportion of seeds from self-pollination contained a large embryo (75%) relative to seeds from cross-pollination (92%). These results suggest that sexual reproduction and recruitment in this rare plant are dependent on the frequency of pollinator visitations that result in outcrossing. Key words: plant conservation, plant breeding systems, inbreeding, self-pollination, orchid. Une consequence importante de l'autocompatibilite chez les plantes est que l'autopollinisation peut avoir des effets deleteres sur la valeur d'adaptation de la plante a cause de l'endogamie. Les auteurs ont realise une experience de pollinisation manuelle dans des conditions de terrain pour mesurer la magnitude de la depression d'endogamie associee a l'autopollinisation de la rare platanthere blanchatre de l'ouest Platanthera praeclara Sheviak et Bowles. En comparant les capsules et les graines resultant de la pollinisation croisee par rapport a l'autopollinisation, ils ont determine que l'autopollinisation reduit la qualite des graines alors qu'elle n'exerce pas d'effet detectable sur la production des capsules ou le nombre de graines. Un plus petit pourcentage de graines resultant de l'autopollinisation contenait un embryon (18 %) relativement aux graines issues de la pollinisation croisee (46 %). Les graines qui contenaient un embryon ont ete classees selon la taille de l'embryon, petite ou grande. Une proportion plus faible de graines issues de l'autopollinisation contenait un embryon de grande taille (75 %) comparativement aux graines issues de la pollinisation croisee (92 %). Ces resultats suggerent que la reproduction sexuee et le recrutement chez cette plante rare sont dependants de la frequence des visites des pollinisateurs qui entrainent le croisement eloigne. [Traduit par la Redaction] Mots-cles : conservation des plantes, systemes de croisement des plantes, endogamie, autopollinisation, orchidee., Introduction The theory regarding the genetics of plant populations has provided predictions regarding the consequences of increasing rarity, particularly for those species in which habitat loss and fragmentation contribute to [...]

In the original paper, Figure 3A has incorrect N values. The N values for Figure 3A should be 20 and 18, not 2 and 1. The correct figure is shown [...]

Solanum carolinensehas a gametophytic self-incompatibility (GSI) system that is typical of the Solanaceae in which pistils produce specific S-RNase proteins that disrupt the growth of pollen tubes sharing the same S-allele. However, unlike most self-incompatible plantsSolanum carolinenseis a weed. Self-incompatibility is uncommon in weeds because disturbed habitats require frequent recolonization (hence populations are repeatedly founded by few individuals bearing a limited number of S-alleles), effective population sizes are small (supporting few S-alleles) and habitats are ephemeral (so there is limited time for the migration of additional S-alleles into populations). We carried out a series of greenhouse experiments using clonal replicates (rhizome cuttings) of plants from two natural populations ofS. carolinenseto determine if there is variation in the strength of GSI within these populations. We found that the growth rate of self-pollen tubes and self-fertility increases with floral age. That is, flowers become more self-compatible as they age. Moreover, we found that self-fertility increases on plants in which the first 20 flowers receive no cross pollen. That is, when few or no fruits are produced on the first 20 flowers, self-pollination is more likely to result in fruit/seed set. Finally, we found that genotypes differ in their degree of self-fertility indicating that there is broadsense heritability for plasticity in the strength of self-incompatibility. These findings indicate that some genotypes ofS. carolinenseare capable of producing self-seed when cross pollen is scarce, even though the plants have a functional GSI system. [ABSTRACT FROM AUTHOR]

For species with bicellular pollen, the attrition of pollen tubes is often greatest where the style narrows at the transition between stigmatic tissue and the transmitting tissue of the style. In this region, the tubes switch from predominantly autotrophic to predominantly heterotrophic growth, the generative cell divides, the first callose plugs are produced, and, in species with RNase-type self-incompatibility (SI), incompatible tubes are arrested. We review the literature and present new findings concerning the genetic, environmental and stylar influences on the performance of pollen before and during the autotrophic-heterotrophic transition of pollen tube growth. We found that the ability of the paternal sporophyte to provision its pollen during development significantly influences pollen performance during the autotrophic growth phase. Consequently, under conditions of pollen competition, pollen selection during the autotrophic phase is acting on the phenotype of the paternal sporophyte. In a field experiment, using Cucurbita pepo, we found broad-sense heritable variation for herbivore-pathogen resistance, and that the most resistant families produced larger and better performing pollen when the paternal sporophytes were not protected by insecticides, indicating that selection during the autotrophic phase can act on traits that are not expressed by the microgametophyte. In a study of a weedy SI species, Solanum carolinense, we found that the ability of the styles to arrest self-pollen tubes at the autotrophic-heterotrophic transition changes with floral age and the presence of developing fruits. These findings have important implications for selection at the level of the microgametophyte and the evolution of mating systems of plants.