Seed Dispersal of an Invasive Shrub, Amur Honeysuckle (Lonicera maackii ), by White-tailed Deer in a Fragmented Agricultural-forest Matrix

Ungulates are potentially important seed dispersers for many invasive plant species. While our understanding of which invasive plant species are dispersed by ungulates has improved over the last decade, the factors influencing this process remain poorly understood. To address this, we explored whitetailed deer (Odocoileus virginianus) seed consumption and dispersal of an invasive shrub (Lonicera maackii) in fragmented agricultural-forest matrices in western Ohio. In a pairwise browse preference experiment, deer browsed at similar levels on branches of L. maackii with fruits removed and fruits intact (mean ± 95 % CI 57 ± 14 and 62 ± 14 %, respectively). We found no evidence that white-tailed deer disperse L. maackii seeds along an invasion front, but 31 % of deer pellet groups collected in an invaded area contained germinable L. maackii seeds (maximum number of germinable seeds = 30). By combining hourly movement data specific to fragmented landscapes and gut retention time data, we projected that female deer disperse 91 %of ingested seeds further than 100 m from seed sources (i.e., long-distance seed dispersal), and rarely disperse seeds up to 7.9 km. We conclude that white-tailed deer can be important long-distance seed dispersal vectors of L. maackii, and that invader abundance and/or patch connectivity likely influence patterns of seed dispersal by white-tailed deer

peromyscus photos

Observations of Peromyscus leucopus activity timing from motion-activated cameras. Cameras were deployed for 6 one-week sessions in spring, summer, and fall of 2017, in plots invaded by buckthorn (Rhamnus cathartica) or plots with buckthorn removed

peromyscus trap entry

Trap-entry times for Peromyscus leucopus collected over one 4-night trapping session during spring 2017, and two 4-night trapping sessions during fall 2017. Mice were trapped in plots invaded by buckthorn (Rhamnus cathartica) and plots with buckthorn removed

Data from: Invasive shrubs modify rodent activity timing, revealing a behavioral rule governing diel activity

Animals adjust the timing of their activity to maximize benefits, such as access to resources, and minimize costs, such as exposure to predators. Despite many examples of invasive plants changing animal behavior, the potential for invasive plants to alter the timing of animal activity remains unexplored. In eastern North America, invasive shrubs might have particularly strong effects on animal activity timing during spring and fall, when many invasive shrubs retain their leaves long after native species’ leaves senesce. We experimentally removed an invasive shrub (buckthorn, Rhamnus cathartica) and monitored the activity timing of a ubiquitous small-mammal species (white-footed mouse, Peromyscus leucopus) in spring, summer, and fall. We captured nearly three times as many P. leucopus in plots invaded by R. cathartica compared to plots with R. cathartica removed, and P. leucopus were captured two hours earlier in invaded plots. Regardless of invasion treatment, P. leucopus appear to follow a common rule to set activity timing: P. leucopus were only active below a threshold of ground-level moonlight illuminance (0.038 lux). Diel and monthly lunar cycles play an important role in regulating small-mammal activity, but our data suggest that decreased light penetration dampens the influence of moonlight illuminance in habitats invaded by R. cathartica, allowing P. leucopus to remain active throughout the night. By changing the temporal niche of ubiquitous native animals, invasive shrubs may have unappreciated effects on many ecological interactions, including processes that alter community diversity and affect human health

Mycorrhizal inoculation mitigates damage from an intermediate, but not severe, frost event for a cool-season perennial bunchgrass

Extreme cold events can damage plant tissues, altering growth and reproduction. Soil fungi may help plants tolerate environmental stressors, but the role these microbes play during episodes of severe cold warrants further examination. Using the bunchgrass Elymus canadensis, we tested how inoculation with mycorrhizal fungi alters plant tolerance to freezing temperatures (tested at -8C and -16C). We found that, regardless of mycorrhizal inoculation, E. canadensis exposed to -16C exhibited greater tissue damage, less tiller growth, and fewer reproductive tillers than plants exposed to control or -8C conditions. Plants exposed to -8C and -16C displayed greater levels of visible damage compared to control plants. Mycorrhizae reduced damaged on tillers in the -8C treatment, but had less effect on tiller damage in control or -16C treatments. Inoculation with AM fungi limited E. canadensis tiller number, but only at the control temperature, suggesting mycorrhizae may impose costs on E. canadensis under benign thermal conditions. Our study demonstrates that extreme temperatures can affect multiple components of E. canadensis growth, and that costs and benefits of AM fungi, where found, depend upon the thermal environment. Our findings reinforce the overarching importance of historically rare, but increasingly common, environmental extremes in shaping the growth of plants.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Seedling responses to decreased snow depend on canopy composition and small-mammal herbivore presence

Winter is becoming warmer and shorter across the northern hemisphere, and reductions in snow depth can decrease tree seedling survival by exposing seedlings to harmful microclimates. Similarly, herbivory by small mammals can also limit the survival and distribution of woody plants, but it is unclear whether winter climate change will alter small-mammal herbivory. Although small-scale experiments show that snow removal can either increase or decrease both soil temperatures and herbivory, we currently lack snow-removal experiments replicated across large spatial scales that are needed to understand the effect of reduced snow. To examine how winter herbivory and snow conditions influence seedling dynamics, we transplanted Acer saccharum and Tsuga canadensis seedlings across a 180 km latitudinal gradient in northern Wisconsin, where snow depth varied seven-fold among sites. Seedlings were transplanted into one of two herbivory treatments (small-mammal exclosure, small-mammal access) and one of two late-winter snow removal treatments (snow removed, snow unmanipulated). Snow removal increased soil freeze-thaw frequency and cumulative growing degree-days (GDD), but the magnitude of these effects depended on forest canopy composition. Acer saccharum survival decreased where snow was removed, but only at sites without conifers. Excluding small mammals increased A. saccharum survival at sites where the small-mammal herbivore Myodes gapperi was present. Excluding small mammals also increased T. canadensis survival in plots with \u3c 5 cm snow. Because variation in canopy composition and M. gapperi presence were important predictors of seedling survival across the snow-depth gradient, these results reveal complexity in the ability to accurately predict patterns of winter seedling survival over large spatial scales. Global change scenarios that project future patterns of seedling recruitment may benefit from explicitly considering interactions between snow conditions and small-mammal winter herbivory