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Interactions between plants and scatter‐hoarding animals may shift from mutualism to predation as a function of the resources available to those animals. Because seed species differ in their nutrient content and defenses to predation, resource selection and cache management by scatter‐hoarders, and thus seed fate, may also depend on the relative availability of different seed types. We tracked the fates of tagged Castanea dentata, Quercus alba, and Q. rubra seeds presented to rodents in pairwise combinations and found that C. dentata, which has moderate dormancy prior to germination, survived better in the presence of Q. alba (no dormancy) than with Q. rubra (longer dormancy). Decisions made by scatter‐hoarders in response to the composition of available seed resources can alter the relationship between masting and seed dispersal effectiveness in individual tree species and may have influenced the evolution of asynchrony among species‐specific masting patterns in temperate forests. In theory, preferential allocation of certain seed species to storage or consumption could also result in indirect apparent predation by one seed species on another.

Abstract As the single opportunity for plants to move, seed dispersal has an important impact on plant fitness, species distributions and patterns of biodiversity. However, models that predict dynamics such as risk of extinction, range shifts and biodiversity loss tend to rely on the mean value of parameters and rarely incorporate realistic dispersal mechanisms. By focusing on the mean population value, variation among individuals or variability caused by complex spatial and temporal dynamics is ignored. This calls for increased efforts to understand individual variation in dispersal and integrate it more explicitly into population and community models involving dispersal. However, the sources, magnitude and outcomes of intraspecific variation in dispersal are poorly characterized, limiting our understanding of the role of dispersal in mediating the dynamics of communities and their response to global change. In this manuscript, we synthesize recent research that examines the sources of individual variation in dispersal and emphasize its implications for plant fitness, populations and communities. We argue that this intraspecific variation in seed dispersal does not simply add noise to systems, but, in fact, alters dispersal processes and patterns with consequences for demography, communities, evolution and response to anthropogenic changes. We conclude with recommendations for moving this field of research forward. Seed dispersal—the single opportunity for plants to move—is important for plant fitness, species distributions and patterns of biodiversity. Models that predict extinction risk of species, range shifts and biodiversity tend to rely on average dispersal distances. However, we know that seed dispersal is highly variable even within a single species (e.g. some seeds go very far and some barely move away from their parent plant, some seeds end up in great quality habitats and some end up on roads). This paper looks at the consequences of this variation in seed dispersal for plants and their ability to respond to future global change.

Although dispersal is critical to plant life history, the relationships between seed traits and dispersal success in animal-dispersed plants remain unclear due to complex interactions among the effects of seed traits, habitat structure, and disperser behavior. We propose that in plants dispersed by scatter-hoarding granivores, seed trait evolution may have been driven by selective pressures that arise from interactions between seedling shade intolerance and predator-mediated caching behavior. Using an optimal foraging model that accounts for cache concealment, hoarder memory, and perceived predation risk, we show that hoarders can obtain cache-recovery advantages by placing caches in moderately risky locations that force potential pilferers to engage in high levels of vigilance. Our model also demonstrates that the level of risk needed to optimally protect a cache increases with the value of the cached food item. If hoarders perceive less sheltered, high-light conditions to be more risky and use this information to protect their caches, then shade-intolerant plants may increase their fitness by producing seeds with traits valued by hoarders. Consistent with this hypothesis, shade tolerance in scatter-hoarded tree species is inversely related to the value of their seeds as perceived by a scatter-hoarding rodent.

The evolution of specific seed traits in scatter-hoarded tree species often has been attributed to granivore foraging behavior. However, the degree to which foraging investments and seed traits correlate with phylogenetic relationships among trees remains unexplored. We presented seeds of 23 different hardwood tree species (families Betulaceae, Fagaceae, Juglandaceae) to eastern gray squirrels (Sciurus carolinensis), and measured the time and distance travelled by squirrels that consumed or cached each seed. We estimated 11 physical and chemical seed traits for each species, and the phylogenetic relationships between the 23 hardwood trees. Variance partitioning revealed that considerable variation in foraging investment was attributable to seed traits alone (27-73%), and combined effects of seed traits and phylogeny of hardwood trees (5-55%). A phylogenetic PCA (pPCA) on seed traits and tree phylogeny resulted in 2 \"global\" axes of traits that were phylogenetically autocorrelated at the family and genus level and a third \"local\" axis in which traits were not phylogenetically autocorrelated. Collectively, these axes explained 30-76% of the variation in squirrel foraging investments. The first global pPCA axis, which produced large scores for seed species with thin shells, low lipid and high carbohydrate content, was negatively related to time to consume and cache seeds and travel distance to cache. The second global pPCA axis, which produced large scores for seeds with high protein, low tannin and low dormancy levels, was an important predictor of consumption time only. The local pPCA axis primarily reflected kernel mass. Although it explained only 12% of the variation in trait space and was not autocorrelated among phylogenetic clades, the local axis was related to all four squirrel foraging investments. Squirrel foraging behaviors are influenced by a combination of phylogenetically conserved and more evolutionarily labile seed traits that is consistent with a weak or more diffuse coevolutionary relationship between rodents and hardwood trees rather than a direct coevolutionary relationship.

Diffuse large B‐cell lymphoma (DLBCL) is the most prevalent subtype of non‐Hodgkin lymphoma (NHL) in domestic dogs, with many similarities to its human counterpart. The progression of the disease is rapid, and treatment must be initiated early to achieve cancer remission and extend life. This study examined the relationship between progression‐free survival (PFS) and microRNA (miRNA) expression in dogs with DLBCL. miRNAs are small non‐coding RNA molecules that typically regulate gene expression post‐transcriptionally. They are involved in several pathophysiological processes, including the growth and progression of cancer. Based on the analysis of small RNA sequencing (sRNA‐seq) data, we validated a group of miRNAs in lymph nodes from 44 DLBCL‐affected dogs with known outcomes. We used quantitative PCR to quantify their expression and report a specific subset of miRNAs is associated with decreased PFS in dogs with DLBCL. The miR‐192‐5p and miR‐16‐5p expression were significantly downregulated in dogs with increased PFS. These results indicate that miRNA profiling may potentially identify dogs with DLBCL that will experience poor outcomes following treatment. Identifying specific miRNAs that correlate with the progression of canine DLBCL could aid the development of individualized treatment regimens for dogs. Our study explores how microRNAs (miRNAs) influence canine diffuse large B‐cell lymphoma (DLBCL) outcomes. We found specific miRNAs linked to shorter survival times, suggesting that miRNA profiling could help predict DLBCL prognosis. This research may lead to personalized dog treatments and be relevant for human lymphoma studies.

1. Seed dispersal is a primary driver, via propagule pressure, of biological invasions. In animal-dispersed plants, theory predicts that indirect ecological interactions at the neighbourhood scale may determine landscape-scale patterns of seed dispersal and predation, and thus invasion. 2. Indirect interactions in seed dispersal may arise between two plant species if shared seed dispersal agents adjust their foraging decisions to the relative frequencies of co-occurring seeds. We used seed-tracking experiments and empirically parameterized simulations to test the hypothesis that an indirect interaction between two plant species, mediated by scatterhoarding rodents that both consume and disperse seeds, affects recruitment of an invasive tree. We predicted that acorns of Quercus rubra (invasive in Central Europe) would experience higher caching (and therefore survival) rates when they co-occurred with native Quercus petraea than when they occurred in isolation, that Q. petraea acorns would survive at lower rates with Q. rubra relative to isolation, and that this interaction would facilitate Q. rubra seedling recruitment in Q. petraea forests. 3. Contrary to expectations, the presence of Q. petraea reduced caching of Q. rubra acorns, and co-occurrence with Q. rubra increased caching of Q. petraea. Thus, a rodent-mediated indirect interaction may be slowing rather than facilitating the Q. rubra invasion. However, our simulations indicate that the magnitude of this indirect interaction will change nonlinearly as Q. rubra becomes more dominant on the landscape, and that the pace of invasion will accelerate as the alien species is released from the rodent-mediated effect of Q. petraea. 4. Synthesis. The presence of native Quercus petraea decreases recruitment rates of Quercus rubra, and consequently, slows down the invasion process. The strong dependence of pairwise interactions on the presence of a third-party species emphasizes the role of indirect interactions in the invasion processes.

1. Both seed predators and herbivores can have profound effects on individual plant growth, reproduction and survival, but their population-level effects are less well understood. While most plants interact with a suite of seed predators and herbivores over their life cycle, few studies incorporate the effects of multiple interacting partners and multiple life stages on plant population growth. 2. We constructed a matrix model using 6 years of data from a rare, seed-producing population of American chestnut (Castanea dentata). We combined field demographic data with published experimental results on the effects of pre-dispersal seed predators (weevils) and post-dispersal seed predators (scatter-hoarding vertebrates) and incorporated the effect of vertebrate herbivores estimated from the field data. We explored the impact of these three different animal interactions for short-term (transient) and long-term (asymptotic) tree population growth. In addition, we used the model to explore the conditions under which scatter hoarding would function as a mutualism. 3. Seed predators had greater effect on both short- and long-term population growth than herbivores. Although weevil infestation can greatly reduce the probability of germination, pre-dispersal seed predators had smaller effects on both short- or long-term population growth than post-dispersal predators. The elasticities of weevil-related parameters were also small. The effect of browsers on both the shortand long-term population growth rate were the smallest of the effects studied. Post-dispersal seed predation affected population growth the most in the interactions studied. The probability of seed removal was among the largest elasticities, similar in magnitude to survival of large trees. 4. Synthesis. Our results indicate that neither weevils nor the intensity of browse damage observed at our study site are likely to hinder tree regeneration or reintroduction, although both reduced population growth. Although researchers and forest managers often assume that seeds are unimportant for long-lived tree populations, our test of this assumption shows that scatterhoarders and other post-dispersal seed consumers can significantly limit natural regeneration. Forest management that alters scatterhoarder behaviour could have significant effects on tree population dynamics that are largely unexplored.

Variation in species richness and density of native birds in urban parks and greenspaces (“parks”) is often substantial. Understanding why differences exist, and whether all migratory guilds are equally affected, is poorly known. We surveyed breeding bird communities in 48 undeveloped forested parks in Portland, Oregon, USA, to determine the contributions of park area, shape, connectivity, landscape composition surrounding parks, and differences in structure/composition of local habitat to variation in richness and density of residents, long-distance migrants, and short-distance/partial migrants. Migratory guilds responded differently to environmental factors. Richness and density of long-distance migrants increased with park area and abundance of small (< 10 cm DBH), mostly native, tree species. Resident richness also increased with the abundance of small trees. However, resident and short-distance/partial migrant richness was independent of park area, and resident density declined with increasing area. Park shape, connectivity, and landscape composition did not influence richness or density of any migratory guilds, possibly because of relatively high tree cover in Portland’s landscape. Separate analyses of forest-dependent species of all migratory guilds revealed that area was the primary contributor to variation in density of residents and long-distance migrants, structural habitat features contributed to variation in density of residents but not long-distance migrants, and that density of long-distance migrants declined with elongated park shape. Few forest-dependent species existed in parks below 10 ha, and their minimum area requirements for maintaining populations were estimated to be 30 to 40 ha. Without such parks most long-distance migrants would likely disappear from Portland’s landscape.

Estimates of utilization distributions (UDs) are used in analyses of home-range area, habitat and resource selection, and social interactions. We simulated data from 12 parent UDs, representing 3 series of increasingly intense space-use patterns (clustering of points around a home site, restriction of locations to a network of nodes and corridors, and dominance of a central hole in the UD) and compared the ability of kernel density estimation (KDE) and local convex hull (LCH) construction to reconstruct known UDs from samples of 10, 50, 250, and 1,000 location points. For KDE, we considered 4 bandwidth selectors: the reference bandwidth, least-squares cross-validation (LSCV), direct plug-in (DPI), and solve-the-equation (STE). For the sample sizes and UD patterns tested here, KDE achieved significantly higher volume-of-intersection (VI) scores with known parent UDs than did LCH; KDE also provided less biased home-range area estimates under many conditions. However, LCH minimized the UD volume that occurred outside the true home range boundary (Vout). Among the KDE bandwidth estimators, relative performance depended on the type and intensity of space use patterns, sample size, and the metric used to evaluate performance. Biologists should use KDE for UD and home range estimation within a probabilistic context, unless their objective is to exclude potentially unused areas by defining the area delimited by data.

Seed predation and rodent foraging behaviors depend on frequency of available seeds and seed traits. However, the interaction of frequency of seed availability and seed traits adds a new level of complexity to granivore–seed dynamics. We conducted experiments with eastern gray squirrels (Sciurus carolinensis) designed to elucidate the frequency × trait interaction. We hypothesized that frequency-dependent caching should occur only among pairs of seeds that are relatively similar in attributes that affect their perceived value as a storable food item. We also tested whether caching decisions were dependent on seeds already cached, a variable rarely considered in seed dispersal studies. Frequency-dependent seed caching occurred when seeds of relatively similar value (Juglans regia and Castanea mollissima) were paired. For this seed pair, caching decisions by S. carolinensis were dependent on seeds already cached such that squirrels tended to cache seeds that were either rare in the environment or in the cache. When seeds of very different caching values were paired (Juglans nigra and Corylusamericana), a strong preference for the high-value seed was observed, but no frequency-dependent selection. We conclude that in pairings of seeds of differential caching value, the highly preferred seed is cached regardless of frequency of availability. In contrast, when seeds of similar value are paired, rarer (more common) seeds are cached at a higher (lower) rate than expected, and this behavior potentially stabilizes seed survival across available seed types leading to increased tree diversity. Our results indicate that caching of seeds by squirrels, and by implication recruitment of seedlings into plant populations, is likely driven by complex interactions between the relative frequency of seeds and their traits. We expect similar patterns to occur in any system in which foragers select among resource types that vary in perceived value.