Both riparian tree species diversity and genetic diversity can influence streams through leaf litter decomposition; however, these two sources of variation have not been compared directly. Here, we compare leaf litter decomposition for a physical mixture of two Populus species to the litter from an F1 hybrid (a genetic mixture) of the same two species. Leaf litter was collected from a common garden for an F1 hybrid between Japanese poplar (Populus maximowiczii A. Henry) and black cottonwood (Populus trichocarpa Torr. & A. Gray ex Hook.), as well as both parent species. Four litterbag treatments consisted of litter from the F1 hybrid, an equal-part mixture treatment of litters from both parents, and litter from each parent in isolation. The hybrid litter had higher C:N content and lower % condensed tannins than either parent species, or the average of the two parents that represented the mixture. While the hybrid and mixture treatments both lost more mass than expected by day 42, the mixture lost relatively more mass than the hybrid and roughly as much as the faster-decomposing P. trichocarpa parent. The hybrid mimicked the mixture, and both supported higher aquatic macroinvertebrate richness and less litter mass remaining than expected based on parent species values, despite differences between the hybrid and mixture in initial phytochemistry.
To allow instructors to reach out and assist students in a timely manner, a student success prediction model aims to identify which students could use help. We focus on hands-on cybersecurity education and the EDURange platform. Because it is difficult to obtain sufficient high-quality data to train the model exclusively through classroom testing, we are employing the 3DG framework to create synthetic data to supplement it. This paper is an in-depth exploration of the tensor decomposition aspect of the 3DG methodology for our use-case by offering a thorough explanation of tensor decomposition, creating a new optimization strategy, and exploring the process on our new dataset. We found that the existing 3DG optimization produced a zero-tensor result, which cannot be used to generate new data points. We make use of the likelihood that if a student answers a question correctly on an early attempt, they are likely to answer it correctly on all subsequent attempts.
The fungus Fusarium xyrophilum produces flower-like structures (i.e. pseudoflowers) composed entirely of mycelia on yellow-eyed grasses (Xyris spp.), including X. surinamensis in Guyana. Whether these pseudoflowers function as true mimics that attract insects for fungal propagule dispersal remains unknown. We evaluated the potential of F. xyrophilum to influence insect visitation patterns by (i) documenting insect visits to real flowers and pseudoflowers on X. surinamensis in the field in Guyana, (ii) assessing the presence of F. xyrophilum DNA on insect bodies, and (iii) analyzing volatile emissions from flowers and pseudoflowers. During our field work, a broad range of generalist insects (i.e. Vespidae, Formicidae, Salticidae, Acrididae, and Tetrigidae) visited the flowers and pseudoflowers, which notably shared some insect visitors (i.e. meadow katydids, carpenter ants, and geometer moths). Some of these insects were observed chewing on the flowers and pseudoflowers. Fusarium xyrophilum DNA was detected on the bodies of captured insects using conventional and quantitative polymerase chain reaction (PCR). Volatile profiles of pseudoflowers and flowers were largely similar, except for a sesquiterpene, putatively identified as α-gurjunene, which was emitted by pseudoflowers and pure cultures of F. xyrophilum but not Xyris flowers. These findings support the role of insect visitors as vectors of F. xyrophilum propagules and suggest that the fungus may attract and use generalist insects by exploiting their preexisting sensory biases for Xyris floral signals rather than true mimicry.
Low native plant establishment is a common restoration challenge for land managers across many ecosystems. Determining the factors contributing to low establishment rates can lead to more efficient use of limited seed resources. This study considers seed predation as a potential factor for low establishment rates. Using exclusion cages, we tested whether small mammals and invertebrates prey on seed from five functionally important plants with less than 5% establishment rates in Pacific Northwest prairie restoration sites: Balsamorhiza deltoidea, Dichanthelium oligosanthes, Armeria maritima, Viola adunca, and Erigeron speciosus. Three other factors were tested to assess their influence on predation: seed size, edge effect, and timing. Five recently burned prairies were studied, each containing three 50 m transects with three plots along a gradient from the unburned edge to the burned interior. Each plot contained four subplots (treatments): insect entry, small mammal entry, complete exclusion (control), and no exclusion. Each treatment contained a seed dish with 20 seeds of each species. Seeds remaining were counted after 24 hr, 48 hr, and 1 wk. A preference by small mammals for larger-sized seeds (B. deltoidea, D. oligosanthes, and V. adunca) was found. No seed predation by insects was observed under the specific conditions of this study. Furthermore, no evidence of an edge effect influencing predation was found, and the majority of seed predation by small mammals was observed at the 1 wk count. These findings suggest that attempting to mitigate seed losses from small mammals could positively influence seedling establishment rates for species with larger seeds.
