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.
Increasing recreational use of natural areas may pose a threat to biodiversity, particularly in sensitive high-elevation ecosystems. Lichens and bryophytes (collectively termed cryptogams here) contribute substantially to biodiversity in almost all terrestrial ecosystems, but their response to disturbance from recreation has rarely been studied. We inventoried lichen and bryophyte communities and analysed impacts of disturbance and environmental variables at four study areas in Mount Rainier National Park, Washington, USA. The study areas ranged from low-elevation, wet temperate forests to alpine environments and adjacent subalpine forests. A total of 77 liverwort taxa, 203 lichen taxa, and 195 moss taxa were found across all study areas, for a total of 475 cryptogam taxa. We found that cryptogam richness increased with increasing distance from trails across all study sites, even as far as 75 m from trails. Negative effects of visitor use on cryptogam communities appeared to be particularly pronounced in alpine areas. Rare cryptogam occurrences were associated with less trampled, wetter, and rockier sites in the alpine zone; we did not identify any drivers of rare cryptogam occurrences in forest areas. Synthesis and applications. Our results highlight that ecological impacts of recreational use may extend great distances from trails and other heavily used areas. Additional efforts by land managers to prevent visitors from walking off-trail in heavily visited areas could help conserve lichen and bryophyte diversity.
