Biology subjects

Ekwealor, J. T. B.

Publications and source records attributed to Ekwealor, J. T. B..

4 recordsLinked to original sources

bioRxiv2026

Epiphytic cryptogam communities differ little despite strong variation in coastal fog exposure

Because mosses and lichens obtain water directly from their surroundings, coastal fog is expected to strongly influence epiphytic cryptogam communities during the long summer droughts of Mediterranean-climate ecosystems. We examined epiphytic mosses and lichens on coyote brush (Baccharis pilularis) across coastal and inland transects on San Bruno Mountain, California, where marine-layer exposure produces a sharp local microclimate gradient. We surveyed coyote brush availability, sampled standardized branches, monitored temperature and relative humidity, and quantified cryptogam occurrence, diversity, morphology, and reproduction. Morphological and chemical identifications were supplemented with molecular markers, while bacterial 16S sequencing was used to characterize cryptogam-associated microbiomes across host taxa and, for the dominant moss Pulvigera pringlei, across transects. Coastal microsites were cooler and more humid, whereas inland microsites experienced substantially greater daytime atmospheric drying demand. Despite this pronounced environmental contrast, cryptogam abundance, reproduction, and visible community composition differed little between transects, although branch-level genus diversity was modestly higher on the coastal transect. Macrolichen lobe or branch length and cryptogam patch area were greater inland in pooled comparisons, but these differences weakened after accounting for taxonomic composition. Bacterial communities differed strongly among cryptogam host taxa, but the P. pringlei microbiome showed no detectable difference in diversity or composition between coastal and inland transects. The broad similarity of cryptogam communities across a strong fog gradient is consistent with buffering of epiphytic cryptogams against fine-scale variation in marine-layer exposure. For the predominantly green-algal lichens in this community, the ability to absorb water vapor from humid air may reduce dependence on direct fog wetting, while host-associated bacterial communities may be structured more strongly by host identity than by local microclimate. Together, our results show that epiphytic cryptogam communities and microbiomes can remain remarkably similar across pronounced microclimatic variation despite modest morphological shifts.

plant biology↗

bioRxiv2023

Syntrichia ruralis: Emerging model moss genome reveals a conserved and previously unknown regulator of desiccation in flowering plants

Water scarcity poses a significant threat to ecosystems in the face of global climate change. Syntrichia ruralis, a dryland moss known for its desiccation tolerance, provides valuable insights into surviving water-limited conditions. In this study, the genome of S. ruralis was sequenced and assembled into 12 chromosomes encompassing 21,169 protein-coding genes. Additionally, 3,199 unplaced scaffolds were identified as non-nuclear and symbiont DNA. Transposable elements (TEs) constitute 51.24% of the genome. Notably, chromosome 12, the largest in size due to its high TE load, was identified as the putative sex chromosome. Comparative analysis with the closely related Syntrichia caninervis genome reveals significant large-scale synteny yet some rearrangements, as well as the occurrence of older duplication events that are shared by both. Desiccation and drought tolerance associated gene families, such as early light-inducible proteins (ELIPs) and late embryogenesis abundant (LEA) proteins, were characterized. In addition to a subset of LEA genes being species-specific, a comparative transcriptomic analysis revealed that some shared LEA genes respond differently to dehydration in these two species. Many ELIPs (9 out of 30) are the product of tandem duplication events. As expected, our analyses revealed the importance of the phytohormone abscisic acid (ABA) in the desiccation response of S. ruralis. A significant number of ABA responsive genes were found to be regulated by S. ruralis orthologs of ABA insensitive 3 (ABI3) and abscisic acid responsive element binding factor 2 (AREB2). Markedly, an uncharacterized, but deeply conserved MYB transcription factor, appears to act as a negative regulator of AREB2 in S. ruralis. Interestingly, we determined that the orthologous MYB TF is also involved in an ABA-dependent stress response in the model flowering plant A. thaliana. In sum, the new genomic resources from this emerging model moss offer new insights into the evolution of desiccation tolerance in land plants.

genomics↗

bioRxiv2022

Ultraviolet radiation and dehydration stress induce overlapping transcriptional and metabolic responses in Syntrichia mosses

O_LIProtection from excess solar radiation and access to sufficient water are important problems for terrestrial plants to solve. Desiccation tolerance (DT), defined as the ability to equilibrate to dry air and resume normal metabolic activity after rehydration, allows organisms to survive dry periods by limiting metabolic activity to periods of moisture availability. We compared separate and combined effects of chronic ultraviolet radiation (UVR) treatments (UV-A and UV-A/B) and a dehydration treatment (as a surrogate for desiccation) in the mosses Syntrichia ruralis and S. caninervis to uncover the nature of correlation between DT and UVR tolerance (UVRT). C_LIO_LIUsing a fully factorial experiment with combined transcriptomics and metabolomics, we tested for cross-talk (overlap in signaling pathways in response to different stressors but separate mechanisms of protection) in the genetic underpinnings of DT and UVRT and cross-tolerance (overlap in the mechanism of protection) these two stressors. C_LIO_LIShared transcriptomic response to the two stressors with no significant interaction between them suggested cross-talk between UVRT and DT for S. caninervis. Phenolic metabolites and transcripts were involved in the response to UVR and dehydration in both species. C_LIO_LISome candidate UVRT genes and metabolites were induced by UVR in S. ruralis, but not S. caninervis, supporting the hypothesis that S. ruralis has a more plastic, acclimatable UVR response than S. caninervis, and that these differences are predictable by their unique interaction with these stressors as poikilohydric organisms. C_LI

plant biology↗

bioRxiv2020

Life under quartz: Hypolithic mosses in the Mojave Desert

Several species of dryland cyanobacteria are known to occur as hypoliths under semi-translucent rocks. In the Mojave Desert, these organisms find refuge from intense solar radiation under milky quartz where moisture persists for a longer period of time than in adjacent soil surface habitat. Desert mosses, which are extremely desiccation-tolerant, can also occur in these hypolithic spaces, though little is known about this unique moss microhabitat and how species composition compares to that of adjacent soil surface communities. To address this question, we deployed microclimate dataloggers and collected moss samples from under and adjacent to 18 milky quartz rocks (quartz mean center thickness 26 {+/-} 15 mm) in a western high elevation Mojave Desert site. Light transmission through Mojave quartz rocks may be as low as 1.2%, and data from microclimate loggers deployed for five months support the hypothesis that quartz provides thermal buffering and higher relative humidity compared to the soil surface. Of the 53 samples collected from hypolith and surface microhabitats, 68% were Syntrichia caninervis, the dominant bryophyte of the Mojave Desert biological soil crust. Tortula inermis accounted for 28% of the samples and 4% were Bryum argenteum. In a comparison of moss community composition, we found that S. caninervis was more likely to be on the soil surface, though it was abundant in both microhabitats, while T. inermis was more restricted to hypoliths, perhaps due to protection from temperature extremes. In our study site, the differences between hypolithic and surface microhabitats enable niche partitioning between T. inermis and S. caninervis, enhancing alpha diversity. This work points to the need to thoroughly consider microhabitats when assessing bryophyte species diversity and modelling species distributions. This focus is particularly important in extreme environments, where mosses may find refuge from the prevailing macroclimatic conditions in microhabitats such as hypoliths.

ecology↗