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The timing of life history traits is central to lifetime fitness and nowhere is this more evident or well studied as in the phenology of flowering in governing plant reproductive success. Recent changes in the timing of environmental events attributable to climate change, such as the date of snowmelt at high altitudes, which initiates the growing season, have had important repercussions for some common perennial herbaceous wildflower species. The phenology of flowering at the Rocky Mountain Biological Laboratory (Colorado, USA) is strongly influenced by date of snowmelt, which makes this site ideal for examining phenological responses to climate change. Flower buds of Delphinium barbeyi, Erigeron speciosus, and Helianthella quinquenervis are sensitive to frost, and the earlier beginning of the growing season in recent years has exposed them to more frequent mid-June frost kills. From 1992 to 1998, on average 36.1% of Helianthella buds were frosted, but for 1999—2006 the mean is 73.9%; in only one year since 1998 have plants escaped all frost damage. For all three of these perennial species, there is a significant relationship between the date of snowmelt and the abundance of flowering that summer. Greater snowpack results in later snowmelt, later beginning of the growing season, and less frost mortality of buds. Microhabitat differences in snow accumulation, snowmelt patterns, and cold air drainage during frost events can be significant; an elevation difference of only 12 m between two plots resulted in a temperature difference of almost 2°C in 2006 and a difference of 37% in frost damage to buds. The loss of flowers and therefore seeds can reduce recruitment in these plant populations, and affect pollinators, herbivores, and seed predators that previously relied on them. Other plant species in this environment are similarly susceptible to frost damage so the negative effects for recruitment and for consumers dependent on flowers and seeds could be widespread. These findings point out the paradox of increased frost damage in the face of global warming, provide important insights into the adaptive significance of phenology, and have general implications for flowering plants throughout the region and anywhere climate change is having similar impacts.

In this paper, we test the mid-domain hypothesis as an explanation for observed patterns of flowering diversity in two sub-alpine communities of insect-pollinated plants. Observed species richness patterns showed an early-season increase in richness, a mid-season peak, and a late-season decrease. We show that a \"mid-domain\" null model can qualitatively match this pattern of flowering species richness, with R⁲ values typically greater than 60%. We find significant or marginally significant departures from expected patterns of diversity for only 3 out of 12 year-site combinations. On the other hand, we do find a consistent pattern of departure when comparing observed versus null-model predicted flowering diversity averaged across years. Our results therefore support the hypothesis that ecological factors shape patterns of flowering phenology, but that the strength or nature of these environmental forcings may differ between years or the two habitats we studied, or may depend on species-specific characteristics of these plant communities. We conclude that mid-domain null models provide an important baseline from which to test departure of expected patterns of flowering diversity across temporal domains. Geometric constraints should be included first in the list of factors that drive seasonal patterns of flowering diversity.

A system comprising 2 species of bumblebess (Bombus appositus and Bombus flavifrons) and 2 species of flowers (Delphinium barbeyi and Aconitum columbianum) in Gothic, Colorado, USA, was manipulated to determine whether resource utilization by each bumblebee species was influenced by the presence of the other species of bumblebee. Each bumblebee species concentrated its foraging efforts on a different flower species, apparently choosing the species whose corolla tube length matched its proboscis length most closely. When each bumblebee species was temporarily removed from its preferred flower species, the remaining bumblebee species increased visitation to the other, previously less—utilized, flower species. The remaining bumblebees visited more flowers per stay in the patch, suggesting that they were finding greater amounts of nectar in the absence of other bumblebee species. These removal experiments demonstrated that the bumblebees were sampling flowers frequently enough and were flexible enough in their foraging behavior to respond rapidly to short—term changes in nectar availability. In another area, where its preferred flower species and the other bumblebee species were absent, B. flavifrons foraged actively on the flower species it rarely used in Gothic. This observation and the experiments demonstrate that resource utilization by a bumblebee species is influenced by the presence of other species and suggest that the phenomenon of competitive release can be observed in bumblebees. In this system,interspecific exploitation competition appears to be the primary mechanism involved in resource partitioning.

Analysis of spatial pattern of the seed bank of an old field in Maryland showed that the seed bank was composed primarily of annual and short-lived perennial species. Tree and shrub species were poorly represented. Seed abundance decreased with depth in the soil. The seeds of all species generally had clustered distributions in the soil. However, there was no trend in mean cluster size within or among species, or at different soil depths. The lack of definite trends indicates that the spatial distributions of seeds are governed primarily by environmental factors, and to a lesser degree by biological factors. The method of spatial pattern analysis developed for this study represents a significant improvement over traditional contiguous quadrat methods. In this method, individuals' positions are mapped in the field using cartesian coordinates, and the quadrat data are subsequently derived mathematically. The resolution of pattern is greatly improved, and several problems that reduce the effectiveness of other methods are eliminated. This method can be used to advantage in any study in which spatial patterns analysis is performed, particularly if the objects can be mapped easily. A comparison of three sampling techniques revealed that the precision of seed-number estimates can be improved by taking a large number of small samples, or by subsampling large whole units with very small subunits. The smaller number of large samples favored by many seed-bank researchers generally results in imprecise seed estimates. This result has implications for spatial studies of any clustered organism.

This study examines the reproductive biology of Linum lewisii Pursh. (Linaceae), a polyphilic species visited by small bees and generalist flies in montane Colorado. L. lewisii plants growing at different sites experience large temporal and spatial variations in pollinator visits. Their ability to attract both dipteran and hymenopteran pollinators allows pollination under varying conditions as pollinator pool composition changes. Although L. lewisii is self-compatible, hand-pollination studies indicate that insects are required for seed production. The relative effectiveness of fly and bee pollinators is assessed in terms of per-visit pollen deposition. Insect visitation patterns are combined with per-visit effectiveness data to evaluate the relative importance of different pollinator groups. Overall, bees tend to be more effective than flies in depositing pollen. However, in many instances flies appear to be responsible for more pollen deposition due to their higher visitation rates

Amino acids are probably ubiquitous components of floral and extrafloral nectars. Although it seems likely that they serve, as sugars do, to reward nectarivores, little is known about the responses to amino acids by flower visitors. The experiments reported here were conducted to determine the responses of honey bees (Apis mellifera) to single amino acids at relatively high concentrations dissolved in an aqueous solution of 30% sucrose. Bees' responses to 24 L-amino acids, 2 DL mixtures, 2 phenolics, and a flavonoid were tested with artificial-flower feeders. The bees' responses were classified as: (1) consumption that generally declined as amino acid concentration increased (although weak solutions of amino acids were sometimes preferred over a sucrose control), (2) a preference for the strongest concentration offered (phenylalanine), (3) no significant difference between the amino and acid and control. There were no apparent correlations between characteristics of the amino acids and the bees' reactions to them, and no obvious difference between responses to essential and nonessential amino acids.

The thistle Jurinea mollis Ascherson is eaten by three types of herbivores, which the plant responds to in different ways. Multiple rosettes are produced on a single root after lepidopteran larvae eat the central part of a basal rosette, and each of these rosettes eventually produces a flower stalk. Plants with multiple stalks can produce up to three times as many seeds as those without multiple stalks. Up to 50% of flowering plants in a study site were found to have multiple stalks. Some plants lose their terminal flower heads to herbivores, probably small mammals. They respond by developing axillary flower heads, which are much less successful than terminal flower heads at producing seeds. Damage caused by moth and tephritid fly larvae to the receptacles of flower heads interrupts the development of seeds, but there is no apparent response by the plant, which may not produce any viable seed. This variety of types of herbivory, with their strikingly different consequences, serves to emphasize the importance of careful consideration of responses of plants to herbivory. /// Чертополох Jurinea mollis Ascherson потребляется тремя типами фитофагов, на которых растение реагирует различными способами. Многочисленные розетки формируются на единственном корне после выдания гусеницами бабочек центральной части базальной розетки, и каждая розетка дает цветочный побег. Растения с многочисленными цветочными побегами могут продцировать втрое больше семян, чем растения без многочисленных побегов. Свыше 50% цветущих растений в исследованном участке имели многочисленные цветочные побеги. У некоторых растений терминальные цветки выдаются фитофагами, вероятно мелкими млекопитающими. Растения реагируют на Это формированием аксиллярных цветков, менее эффективных, чем терминальные в отношении продукции семян. Ущерб, наносимый гусеницами бабочек и личинками мух пестрокрылок цветоложу, нарушает развитие семян, но это не вызывает ответной реакции растений, которые не могут давать жизнеспособных семян. Эти различия в воздействии фитофагов с их четко различающимися последствиями подчеркивают важность тщательного изучения реакций растений, на повреждения фитофагов.

Helianthella quinquenervis (Asteraceae), the aspen sunflower, secretes sugar and amino acid rich nectar from involucral bracts during bud and flowering stages. The nectar is usually collected by ants as fast as it is secreted. H. quinquenervis is subject to predispersal seed predation by larvae of several insect species, primarily tephritid flies, an agromyzid fly, and 3 Lepidoptera. When present, ants interrupt oviposition efforts by the female flies but do not appear to be effective against lepidopteran or mammalian herbivores. The degree of protection by ants conferred upon plants was investigated by excluding ants from some plants and by correlating ant density with subsequent damage to ovules and developing seeds. At higher elevations (2896 and 3091 m) damage to plants with ants was significantly reduced compared with plants without ants. At a lower elevation (2734 m) where seed predator and ant densities were highest, the ants were less effective as deterrents and predation on ovules and seeds usually exceeded 60%. Flowers of some other composite species in the same habitats appear to be more effectively protected from predation by chemical deterrents, raising questions of the relative benefits of chemical deterrents compared to ants as a means of protection.