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

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

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

Sin Nombre virus prevalence from 2014–2017 in wild deer mice, Peromyscus maniculatus, on five of the California Channel Islands

Sin Nombre virus (SNV) is a zoonotic virus that is highly pathogenic to humans. The deer mouse, Peromyscus maniculatus, is the primary host of SNV, and SNV prevalence in P. maniculatus is an important indicator of human disease risk. Because the California Channel Islands contain permanent human settlements, receive hundreds of thousands of visitors each year, and can have extremely high densities of P. maniculatus, surveillance for SNV in island P. maniculatus is important for understanding the human risk of zoonotic disease. Despite the importance of surveillance on these heavily utilized islands, SNV prevalence (i.e. the proportion of P. maniculatus that test positive to antibodies to SNV) has not been examined in the last 13–27 years. We present data on 1,610 mice sampled for four consecutive years (2014–2017) on five of the California Channel Islands: East Anacapa, Santa Barbara, Santa Catalina, San Nicolas, and San Clemente. Despite historical data indicating SNV-positive mice on San Clemente and Santa Catalina, we detected no SNV-positive mice on these islands, suggesting very low prevalence or possible loss of SNV. Islands historically free of SNV (East Anacapa, Santa Barbara, and San Nicolas) remained free of SNV, suggesting that rates of pathogen introduction from other islands and/or the mainland are low. Although continued surveillance is warranted to determine whether SNV establishes on these islands, our work helps inform current human disease risk in these locations and suggests that SNV prevalence on these islands is currently very low

Sin Nombre virus prevalence from 2014–2017 in wild deer mice, Peromyscus maniculatus

Sin Nombre virus (SNV) is a zoonotic virus that is highly pathogenic to humans. The deer mouse, Peromyscus maniculatus, is the primary host of SNV, and SNV prevalence in P. maniculatus is an important indicator of human disease risk. Because the California Channel Islands contain permanent human settlements, receive hundreds of thousands of visitors each year, and can have extremely high densities of P. maniculatus, surveillance for SNV in island P. maniculatus is important for understanding the human risk of zoonotic disease. Despite the importance of surveillance on these heavily utilized islands, SNV prevalence (i.e. the proportion of P. maniculatus that test positive to antibodies to SNV) has not been examined in the last 13–27 years. We present data on 1,610 mice sampled for four consecutive years (2014–2017) on five of the California Channel Islands: East Anacapa, Santa Barbara, Santa Catalina, San Nicolas, and San Clemente. Despite historical data indicating SNV-positive mice on San Clemente and Santa Catalina, we detected no SNV-positive mice on these islands, suggesting very low prevalence or possible loss of SNV. Islands historically free of SNV (East Anacapa, Santa Barbara, and San Nicolas) remained free of SNV, suggesting that rates of pathogen introduction from other islands and/or the mainland are low. Although continued surveillance is warranted to determine whether SNV establishes on these islands, our work helps inform current human disease risk in these locations and suggests that SNV prevalence on these islands is currently very low