American Journal of Botany最新文献

Understanding and predicting plant responses to biotic and abiotic environments necessitates grappling with thousands of microbial interactions occurring within aboveground and belowground plant tissues. These distinct microbial communities are indirectly connected through their plant hosts, and aboveground-belowground (AGBG) microbial interactions could play large roles in plant health and drive plant community and ecosystem-level responses. In this review and synthesis, we first discuss mechanisms through which focal microbes directly and indirectly affect other microbes in distal plant compartments. We then add in a layer of complexity: How might microbial community interactions within aboveground plant organs affect root-associated microbiomes, and vice versa? We point to gaps in our knowledge that should drive future research agendas on how “discrete” microbial communities within plants influence one another—a key feature currently missing in plant microbiome research. We also discuss the utility of applying existing ecological theory to enhance the predictive power of plant microbiome research, particularly regarding the outcomes of AGBG microbial interactions across diverse environmental and ecological contexts. These efforts will be especially important within fields such as sustainable agriculture that seek to harness plant-microbiome interactions within a changed and ever-changing world.

Premise: Evolutionary theory predicts polymorphism should be rare; however, intraspecific variation in floral color is common and can be attributed to genetic drift, plasticity, or variable selection. Examining floral color polymorphism both within contact zones and across a species' range can reveal the mechanisms maintaining this variation. Here, we used a multistep approach to investigate spatially heterogeneous variation in floral bract color in Castilleja coccinea.

Methods: We compared frequencies of color morphs, floral morphology, fitness, and genetic structure in regional populations and in a common garden. Next, we examined habitat differences, including edaphic factors, as potential drivers of variation. Lastly, we leveraged herbarium and iNaturalist occurrence data to investigate whether patterns were consistent at the landscape scale.

Results: Bract color in C. coccinea is genetically heritable, with yellow dominant over red, and is under selection. Populations are predominantly monomorphic, with color distance showing no correlation to genetic or geographic distance, despite significant genetic isolation by distance. Yellow morphs were associated with open wetlands, while red morphs occurred at drier sites with nearby tree cover. Red morphs demonstrated lower fitness in a common garden, suggesting trade-offs associated with pleiotropic effects of floral color.

Conclusions: Differences in floral color between morphs are consistent with diversification associated with a shift in ecological niche. We identified variation in edaphic and habitat conditions as probable drivers of divergence in floral color. Additionally, variation in other floral traits suggests a combined role of pollinators and habitat differences acting in concert to maintain distinct floral color morphs.

Premise: Floral pigments primarily serve to attract pollinators through color display and also contribute to protection against environmental stress. Although pigment composition can be plastically altered under stress, its impact on pollinator color perception remains poorly understood. Moricandia arvensis (Brassicaceae) exhibits seasonal floral dimorphism, with lilac spring flowers and white summer flowers. This study examines how heat-driven shifts in floral pigments alter flower color and its perception by pollinators.

Methods: We conducted a comparative analysis of spring and summer floral morphs in a natural population by measuring petal spectral reflectance, analyzing absorption spectra of petal extracts, and modeling floral color in the visual systems of major pollinator functional groups. Additionally, UHPLC-ESI-MS/MS analysis was conducted under controlled conditions to characterize differences in phenolic profiles.

Results: Spring flowers exhibited strong UV reflectance and a reduction in reflectance in the green spectrum, whereas summer flowers showed no UV reflectance and high reflectance in the visible range. Anthocyanins were detected only in spring flowers, while summer flowers accumulated high levels of UV-absorbing flavonoids. Despite these differences, both floral morphs remained visually conspicuous to hymenopterans, dipterans, lepidopterans, and coleopterans. Summer flowers produced twice as many phenolic compounds and accumulated higher concentrations, with ferulic acid and kaempferol derivatives the most prominent.

Conclusions: White summer flowers of Moricandia arvensis are not merely anthocyanin-deficient but exhibit a distinct profile of UV-absorbing phenolics that may confer heat tolerance while preserving floral conspicuousness to pollinators. These findings highlight the role of multifunctional traits in the evolution of flower color.