Alpine Botany最新文献

Plant reproduction in alpine environments is affected by climate both directly through climate impacts on growth and phenology, and indirectly through impacts on the biotic interactions affecting pollination success. These effects can be highly variable in time and space. In this study we investigated how different abiotic and biotic factors influence reproductive investment and success in populations of Ranunculus acris across an alpine landscape over a two-year period. In an alpine area at Finse, southern Norway, we measured reproductive investment (total seed mass) and reproductive success (seed-set rate) in 38 sites differing in temperature (related to elevation) and length of the growing season (related to time of snowmelt). To assess biotic interactions, we measured floral density and pollinator visits and conducted a supplemental pollen experiment. Reproductive investment and success increased with temperature, but only when floral density and/or number of pollinator visits was high, and only in the warmer year (2016). Reproduction in R. acris was pollen-limited in both years, especially at warmer temperature and in sites with early snowmelt. Pollinator visits increased with temperature and with higher floral density, suggesting a shift in relative importance of the biotic factors (from plants to pollinators) in limiting reproduction with increasing temperature. Our study shows that reproductive investment and success in R. acris is affected by climate through the interactive effects of abiotic and biotic processes. These effects vary between years and across the landscape, suggesting a potential for larger-scale buffering of climate change effects in heterogeneous landscapes.

There is wide consensus that climate change will seriously impact flowering plants and their pollinators. Shifts in flowering phenology and insect emergence as well as changes in the functional traits involved can cause alterations in plant-pollinator interactions, pollination success and plant reproductive output. Effects of rising temperatures, advanced snowmelt and altered precipitation patterns are expected to be particularly severe in alpine habitats due to the constrained season and upper range margins. Yet, our understanding of the magnitude and consequences of such changes in life history events and functional diversity in high elevation environments is incomplete.

This special issue collects novel insights into the effects of climate change on plant-pollinator interactions in individual plant species and on network structure of entire plant and pollinator communities in alpine ecosystems. Using simulated changes of earlier snowmelt, natural gradients of variation in temperature, precipitation and snowmelt, or a long-term monitoring approach, these studies illustrate how plant species, plant communities, and pollinators respond to variation in environmental conditions associated with scenarios of ongoing climate change.

The collection of papers presented here clearly demonstrates how spatial or temporal variation in the environmental climatic context affects flower abundances and plant community composition, and the consequences of these changes for pollinator visitation, pollination network structure, pollen transfer dynamics, or seed production. As changes in the availability of flowers, fruits, and seeds are likely to impact on other trophic levels, the time is ripe and pressing for a holistic multitrophic view of the effects of climate change on biotic interactions in alpine ecological communities.

Climate change is altering interactions among plants and pollinators. In alpine ecosystems, where snowmelt timing is a key driver of phenology, earlier snowmelt may generate shifts in plant and pollinator phenology that vary across the landscape, potentially disrupting interactions. Here we ask how experimental advancement of snowmelt timing in a topographically heterogeneous alpine-subalpine landscape impacts flowering, insect pollinator visitation, and pathways connecting key predictors of plant-pollinator interaction. Snowmelt was advanced by an average of 13.5 days in three sites via the application of black sand over snow in manipulated plots, which were paired with control plots. For each forb species, we documented flowering onset and counted flowers throughout the season. We also performed pollinator observations to measure visitation rates. The majority (79.3%) of flower visits were made by dipteran insects. We found that plants flowered earlier in advanced snowmelt plots, with the largest advances in later-flowering species, but flowering duration and visitation rate did not differ between advanced snowmelt and control plots. Using piecewise structural equation models, we assessed the interactive effects of topography on snowmelt timing, flowering phenology, floral abundance, and pollinator visitation. We found that these factors interacted to predict visitation rate in control plots. However, in plots with experimentally advanced snowmelt, none of these predictors explained a significant amount of variation in visitation rate, indicating that different predictors are needed to understand the processes that directly influence pollinator visitation to flowers under future climate conditions. Our findings demonstrate that climate change-induced early snowmelt may fundamentally disrupt the predictive relationships among abiotic and biotic drivers of plant-pollinator interactions in subalpine-alpine environments.

Flowering phenology of alpine plant communities is determined by the interaction between abiotic and biological factors. Bees and flies are major pollinators in alpine ecosystems. The abundance of bumble bees consistently increases with seasonal progress reflecting the colony development cycle, while fly abundance fluctuates unpredictably. Responding to the seasonal dynamics of pollinators, flowering phenology of alpine communities is expected to vary between bee-visited and fly-visited plants within and among regions. We compared the relationship between flower-visitor composition and flowering phenology across geographic regions: fly-dominated New Zealand alpine, subtropical Taiwan alpine, mid-latitudinal alpines in central and northern Japan, and high-elevation Mongolian grassland. Thermal gradient was a fundamental factor regulating flower patterns across regions, and clear seasonality at higher latitudes created diverse flower patterns within communities. Floral abundance of fly-visited plants was less predictable with large variation, whereas that of bee-visited plants showed consistent patterns across regions reflecting the seasonality of bee activity. In New Zealand, most plants were linked to syrphid and/or non-syrphid flies. The network structures of the East Asian alpines were commonly constituted by syrphid flies, non-syrphid flies, and bumble bees, and these groups had specific niche width. In the Mongolian grassland, many insect groups formed diverse networks with small niche overlap. Overall, bumble bees are suggested to be a driver of diverse flowering phenology in alpine ecosystems. In contrast, flies may not be a powerful driver of flowering phenology. Pollination networks between bumble bees and alpine plants are expected to be sensitive to climate change.

Pollen-mediated gene flow and spatial genetic structure have rarely been studied in alpine plants that are pollinated by dipteran insects. In particular, it is not clear how different floral traits, such as floral gender, phenology, and ancillary traits, may affect pollen dispersal distance within alpine plant populations. In this study, we conducted a paternity analysis to track pollen flow in a population of Pulsatilla alpina, an andromonoecious alpine herb producing male and bisexual flowers. We found that the pollen was dispersed over short distances (mean = 3.16 m), with a dispersal kernel following a Weibull distribution. Nonetheless, spatial genetic structure was weak in the population (Sp statistic = 0.013), pointing to effective seed dispersal and/or high inbreeding depression. The pollen dispersal distance was independent of the gender of the flower of origin but depended positively on floral stalk height and negatively on flowering date and tepal length. Although male siring success did not correlate with pollen dispersal distance, selection may favour traits that increase the pollen dispersal distance as a result of reduced bi-parental inbreeding. Our study not only provides new insights into the nature of pollen dispersal of alpine plants, but also reveals the effects of floral traits on a component of male reproductive success.