Biology subjects

Munkres, I.

Publications and source records attributed to Munkres, I..

3 recordsLinked to original sources

bioRxiv2026

Plant microbiomes have a greater effect than plant size on flowering and growth in Asclepias syriaca

Plants strike a balance between growth and defense. The calculus of how to defend against herbivores, and maximize growth and reproduction, can differ between annuals and perennials. Annuals have a live fast, reproduce young strategy; while perennials may maximize fecundity over years. Milkweed, a herbaceous perennial, is a mix of these two strategies. On one hand, a single individual ramet is functionally a herbaceous annual and vulnerable to herbivory. On the other hand, below ground connections allow ramets to share resources and persist for multiple years, perhaps lowering the cost of localized herbivory. Here, we study the impact of herbivory on the leaf and soil microbiome on milkweed growth and flowering in naturally occurring populations. After controlling for plant size and plant genotype, we asked how the microbiome composition was related to flowering time and growth. We find that the leaf microbiome is a strong predictor of plant growth rate, but not flowering. Conversely, we find that the soil microbiome and plant size predict flowering probability. We found no evidence that herbivory altered the leaf or soil microbiome composition. Together these results provide evidence that plant microbiomes also influence growth and fecundity in natural populations of milkweed. These results also provide evidence that the leaf microbiome in milkweed is stable in the face of herbivory. This study expands our knowledge of the contribution of microbiomes to plant demography in a clonal perennial plant.

ecology↗

bioRxiv2021

Nectar bacteria stimulate pollen germination and bursting to enhance their fitness

For many flower visitors, pollen is the primary source of non-carbon nutrition, but pollen has physical defenses that make it difficult for consumers to access nutrients. Nectar-dwelling microbes are nearly ubiquitous among flowers and can reach high densities, despite the fact that floral nectar is nitrogen limited, containing only very low concentrations of non-carbon nutrients. Pollen contains trace micronutrients and high protein content but is protected by a recalcitrant outer shell. Here, we report that a common genus of nectar-dwelling bacteria, Acinetobacter, exploits pollen nutrition by inducing pollen germination and bursting. We use time course germination assays to quantify the effect of Acinetobacter species on pollen germination and pollen bursting. Inoculation with Acinetobacter species resulted in increased germination rates within 15 minutes, and bursting by 45 minutes, as compared to uninoculated pollen. The pollen germination and bursting phenotype is density-dependent, with lower concentrations of A. pollinis SCC477 resulting in a longer lag time before the spike in germination, which is then closely followed by a spike in bursting. Lastly, A. pollinis grows to nearly twice the density with germinable pollen vs ungerminable pollen, indicating that their ability to induce and exploit germination plays an important role in rapid growth. To our knowledge, this is the first direct test of non-plant biological induction of pollen germination, as well as the first evidence of induced germination as a method of nutrient procurement, as the microbes appear to hijack the pollens normally tightly controlled germination mechanisms for their benefit. Our results suggest that further study of microbe-pollen interactions may inform many aspects of pollination ecology, including microbial ecology in flowers, the mechanisms of pollinator nutrient acquisition from pollen, and cues of pollen germination for plant reproduction.

ecology↗

bioRxiv2020

Fungi are more dispersal-limited than bacteria among flowers

Variation in dispersal ability among taxa affects community assembly and biodiversity maintenance within metacommunities. Although fungi and bacteria frequently coexist, their relative dispersal abilities are poorly understood. Nectar-inhabiting microbial communities affect plant reproduction and pollinator behavior, and are excellent models for studying dispersal of bacteria and fungi in a metacommunity framework. Here, we assay dispersal ability of common nectar bacteria and fungi in an insect-based dispersal experiment. We then compare these results to the incidence and abundance of culturable flower-inhabiting bacteria and fungi within naturally occurring flowers across two coflowering communities in California across two flowering seasons. Our microbial dispersal experiment demonstrates that bacteria disperse among habitat patches more readily than fungi via thrips. Across all flowers, bacterial and fungal incidence and abundance were positively correlated but bacteria were much more widespread, suggesting shared dispersal routes or habitat requirements but differences in dispersal and colonization frequency. The finding that bacteria are more common among flowers sampled here, in part due to superior insect-mediated dispersal, may have broad relevance for microbial life-history, community assembly of microbes and plant-pollinator interactions.

ecology↗