High-sensitivity electronic Stark spectrometer featuring a laser-driven light source.

We report developmental details of a high-sensitivity Stark absorption spectrometer featuring a laser-driven light source. The light source exhibits intensity fluctuations of ∼0.3% over timescales ranging from 1 min to 12 h, minimal drift (≤0.

Flavin Charge Redistribution upon Optical Excitation Is Independent of Solvent Polarity.

Flavin absorption spectra encode molecular details of the flavin's local environment through coupling of local electric fields with the chromophore's charge redistribution upon optical excitation. Translating experimentally measured field-tuned transition energies to local electric field magnitudes and directions across a wide range of field magnitudes requires that the charge redistribution be independent of the local field. We have measured the charge redistribution upon optical excitation of the derivatized flavin TPARF in the non-hydrogen-bonding, nonpolar solvent toluene, with and without a tridentate hydrogen-bonding ligand, DBAP, using electronic Stark spectroscopy.

The cost of self-promotion: ecological and demographic implications of the mentor effect in natural plant populations.

Under the mentor effect, compatible heterospecific pollen transfer induces self-pollen germination in otherwise self-incompatible plants. The mentor effect could be considered a novel mode of reproductive interference if it negatively impacts fitness. Yet to date, this phenomenon has predominately been investigated under experimental conditions rather than in situ.

Unusual reactivity of a flavin in a bifurcating electron-transferring flavoprotein leads to flavin modification and a charge-transfer complex.

From the outset, canonical electron transferring flavoproteins (ETFs) earned a reputation for containing modified flavin. We now show that modification occurs in the recently recognized bifurcating (Bf) ETFs as well. In Bf ETFs, the 'electron transfer' (ET) flavin mediates single electron transfer via a stable anionic semiquinone state, akin to the FAD of canonical ETFs, whereas a second flavin mediates bifurcation (the Bf FAD).

Climate driven disruption of transitional alpine bumble bee communities.

Pollinators at high elevations face multiple threats from climate change including heat stress, failure to phenological match advancing flower resources and competitive pressure from range-expanding species of lower elevations. We conducted long-term multi-site surveys of alpine bumble bees to determine how phenology of range-stable and range-expanding species is responding to climate change. We ask whether bumble bee responses generate mismatches with floral resources, and whether these mismatches in turn promote community disruption and potential species replacement.

Stark Spectroscopy of Lumichrome: A Possible Candidate for Stand-Off Detection of Bacterial Quorum Sensing.

Lumichrome (7,8-dimethylalloxazine, LC) is a natural photodegradation product and catabolite of flavin coenzymes. Although not a coenzyme itself, LC is used for biosignaling in plants and single-celled organisms, including quorum sensing in the formation of biofilms. The noninvasive detection of in vivo lumichrome would be useful for monitoring this signaling event.

Sexual and natural selection on pollen morphology in Taraxacum.

Premise: Spiny pollen has evolved independently in multiple entomophilous lineages. Sexual selection may act on exine traits that facilitate male mating success by influencing the transfer of pollen from the anther to the body of the pollinator, while natural selection acts to increase pollen survival. We postulated that relative to sexual congeners, apomictic dandelions undergo relaxed selection on traits associated with male mating success.

Measuring electronic structure properties of flavins and flavoproteins by electronic Stark spectroscopy.

The optical spectrum of a flavoprotein is one of its signature properties. No two flavoprotein absorption spectra are exactly alike as each encodes the details of the interaction of the flavin cofactor electronic structure with the specific protein binding pocket. Electronic Stark spectroscopy has the potential to elucidate these interactions with high sensitivity, at low cost, and requiring minimal technical sophistication.

Does body size predict the buzz-pollination frequencies used by bees?

Body size is an important trait linking pollinators and plants. Morphological matching between pollinators and plants is thought to reinforce pollinator fidelity, as the correct fit ensures that both parties benefit from the interaction. We investigated the influence of body size in a specialized pollination system (buzz-pollination) where bees vibrate flowers to release pollen concealed within poricidal stamens.

How shrub encroachment under climate change could threaten pollination services for alpine wildflowers: A case study using the alpine skypilot, .

Unlabelled: Under climate change, shrubs encroaching into high altitude plant communities disrupt ecosystem processes. Yet effects of encroachment on pollination mutualisms are poorly understood. Here, we probe potential fitness impacts of interference from encroaching (willows) on pollination quality of the alpine skypilot, .

Flight of the bumble bee: Buzzes predict pollination services.

Multiple interacting factors drive recent declines in wild and managed bees, threatening their pollination services. Widespread and intensive monitoring could lead to more effective management of wild and managed bees. However, tracking their dynamic populations is costly.

Functional mismatch in a bumble bee pollination mutualism under climate change.

Ecological partnerships, or mutualisms, are globally widespread, sustaining agriculture and biodiversity. Mutualisms evolve through the matching of functional traits between partners, such as tongue length of pollinators and flower tube depth of plants. Long-tongued pollinators specialize on flowers with deep corolla tubes, whereas shorter-tongued pollinators generalize across tube lengths.

High-altitude multi-taskers: bumble bee food plant use broadens along an altitudinal productivity gradient.

We use an extensive historical data set on bumble bee host choice collected almost 50 years ago by L. W. Macior (Melanderia 15:1-59, 1974) to examine how resource partitioning by bumble bees varies over a 2,700-m altitudinal gradient at four hierarchical scales: individual, colony, species and community.

Tracing impacts of partner abundance in facultative pollination mutualisms: from individuals to populations.

Partner abundance affects costs and benefits in obligate mutualisms, but its role in facultative partnerships is less clear. We address this gap in a pollination web consisting of two clovers (Trifolium) that differ in specialization on a bumble bee pollinator Bombus balteatus. We examine how pollination niche breadth affects plant responses to pollinator abundance, comparing early-flowering (specialized) and late-flowering (generalized) cohorts of T.

Between a rock and a hard place: impact of nest selection behavior on the altitudinal range of an alpine ant, Formica neorufibarbis.

Formica neorufibarbis Emery is a dominant alpine ant in North America. Above timberline, colonies nest under rocks, placing brood against the rock surface to warm during the day. We tested the hypothesis that nest rock preference represents a mechanism of behavioral thermoregulation and used a demographic model to explore its impact on the species' altitudinal range.

Soil fungal effects on floral signals, rewards, and aboveground interactions in an alpine pollination web.

Premise Of The Study: Plants interact with above- and belowground organisms; the combined effects of these interactions determine plant fitness and trait evolution. To better understand the ecological and evolutionary implications of multispecies interactions, we explored linkages between soil fungi, pollinators, and floral larcenists in Polemonium viscosum (Polemoniaceae).

Methods: Using a fungicide, we experimentally reduced fungal colonization of krummholz and tundra P.

Dosage-dependent impacts of a floral volatile compound on pollinators, larcenists, and the potential for floral evolution in the alpine skypilot Polemonium viscosum.

All volatile organic compounds (VOCs) vary quantitatively, yet how such variation affects their ecological roles is unknown. Because floral VOCs are cues for both pollinators and floral antagonists, variation in emission may have major consequences for costs and benefits in plant-pollinator interactions. In Polemonium viscosum, the emission rate for the floral VOC 2-phenylethanol (2PE) spans more than two orders of magnitude.

MECHANISMS OF TOLERANCE TO FLORAL LARCENY IN TWO WILDFLOWER SPECIES.

Tolerance of foliar damage is widely recognized as an effective defense against herbivores and pathogens. However, tolerance of the impacts of antagonists on pollination success is less well understood. Here, we extend the framework of tolerance to foliar damage to understand how plants mitigate the pollination and fitness costs of floral larceny (i.

Density-dependent effects of ants on selection for bumble bee pollination in Polemonium viscosum.

Mutualisms are commonly exploited by cheater species that usurp rewards without providing reciprocal benefits. Yet most studies of selection between mutualist partners ignore interactions with third species and consequently overlook the impact of cheaters on evolution in the mutualism. Here, we explicitly investigate how the abundance of nectar-thieving ants (cheaters) influences selection in a pollination mutualism between bumble bees and the alpine skypilot, Polemonium viscosum.

Stage-dependent patterns of drought tolerance and gas exchange vary between sexes in the alpine willow, Salix glauca.

Females and males of sexually dimorphic species have distinct resource demands due to differential allocation to reproduction. Sexual allocation theory predicts that functional traits will diverge between sexes to support these demands. However, such dimorphism may be masked by the impact of current reproduction on source-sink interactions between vegetative and reproductive organs.

Light-sensing in roots.

Light gradients in the soil have largely been overlooked in understanding plant responses to the environment. However, roots contain photoreceptors that may receive ambient light through the soil or piped light through the vascular cylinder. In recent experiments we demonstrated linkages between phototropin-1 photoreceptor production, root growth efficiency, and drought tolerance, suggesting that root plasticity in response to light signals contributes to the ecological niche of A.

Functional ecology of a blue light photoreceptor: effects of phototropin-1 on root growth enhance drought tolerance in Arabidopsis thaliana.

* The blue light photoreceptor phototropin-1 has been shown to enhance fitness in Arabidosis thaliana under field conditions. Here, we ask whether performance consequences of phototropin-1 reflect its impact on root growth and drought tolerance. * We used a PHOT1-GFP gene construct to test whether phototropin-1 abundance in roots is highest at shallow soil depths where light penetration is greatest.

Solar furnaces or swamp coolers: costs and benefits of water use by solar-tracking flowers of the alpine snow buttercup, Ranunculus adoneus.

Solar tracking or heliotropism simultaneously raises organ temperature and light interception. For leaves and flowers carbon gain is maximized at the expense of water loss. In this study I explore how costs and benefits associated with water use by solar-tracking flowers of the alpine snow buttercup, Ranunculus adoneus change with ambient temperature.

Drought tolerance in the alpine dandelion, Taraxacum ceratophorum (Asteraceae), its exotic congener T. officinale, and interspecific hybrids under natural and experimental conditions.

We compared water relations and adaptations to drought stress in native and invasive exotic dandelions, Taraxacum ceratophorum and T. officinale. Photosynthesis (A), transpiration (E), and water use efficiency (WUE; carbon gained/water lost) were measured for the two species under extreme drought in the alpine tundra of Colorado, USA.

Ecophysiology of first and second generation hybrids in a natural plant hybrid zone.

Hybrids between related species vary widely in relative fitness, and that fitness can depend upon the environment. We investigated aspects of physiology that might influence fitness patterns in a plant hybrid zone. Seeds of Ipomopsis aggregata, I.