Rubus Allegheniensis Research Articles

Surviving or thriving? Trade-offs between growth, defense, and reproduction in a native versus an invasive Rubus

Little is known about limits to reproduction in plants, especially as to how their other life history functions (growth and defense) may constrain reproductive investment. Understanding these constraints can help researchers refine best practices for cultivating species like Rubus (Rosaceae) that produce nutritious fruits as well as for controlling invasive species. Here, we sought to elucidate potential trade-offs between growth, defense, and reproduction in native Rubus allegheniensis Porter (common blackberry) and invasive Rubus phoenicolasius Maxim. (wineberry) while accounting for the effects of varying insect herbivory and resource availability levels. We observed traits related to physical defense (e.g., prickle intensity), growth (e.g., cane length), and floral reproduction (e.g., ripe fruits), as well as carbon availability (e.g., canopy cover). We then used multiple regressions to characterize relationships between these variables for both species. We found potential evidence for 2 induced defenses in the invasive wineberry. Also, 5 models returned significant results indicative of trade-offs between reproduction and growth, reproduction and defense, and defense and growth in a single or both species. Our results highlight the importance of understanding the defensive strategies utilized by these species because inducible defenses may result in trade-offs that could reduce yields and (or) increase the invasive potential of Rubus species.

An omnivorous mesopredator modifies predation of omnivore‐dispersed seeds

AbstractPost‐dispersal seed predation is an important determinant of plant recruitment. Although many plant species are dispersed following consumption by omnivorous vertebrates, the potential for these dispersal agents to indirectly affect seed fate by modifying seed predator behavior is poorly understood. We evaluated the hypothesis that the scat of an omnivorous vertebrate (coyote, Canis latrans), which is also a rodent predator, would reduce seed predation by rodent granivores. We also hypothesized that scat would lead to increased removal by arthropod seed predators by providing a resource that attracts ants and other arthropods. We examined the role of omnivore deposition on seed predation of two animal‐dispersed species that differed in size: Larger Prunus serotina seeds are attacked only by rodents, whereas smaller Rubus allegheniensis seeds are attacked by arthropods and rodents. Using an experiment that manipulated the presence of coyote scat and access by different granivore guilds, we found that scat reduced the total number of seeds removed from full‐access depots by 12%, but it increased the total number of seeds removed from arthropod‐only depots by 43%. Rodent removal of P. serotina seeds was 21% lower in the presence of scat. Scat composition was also important in affecting rodent seed predation, with seed predation 50% lower in the presence of meat‐rich scat compared with mixed or fruit‐rich scat. Arthropod removal of R. allegheniensis seeds was 43% higher in the presence of scat. Prunus serotina seeds were generally removed at greater rates than R. allegheniensis seeds in full‐access trays; however, scat reduced this difference in removal rates from 37% more P. serotina seeds removed to 18% more P. serotina seeds removed. These findings illuminate a new pathway through which omnivores may influence plant populations by modifying post‐dispersal seed predation by arthropods and rodents. Moreover, our results indicate that the ultimate effect of vertebrate omnivores on seed survival in a given region may depend upon omnivore diet, dominant seed predator guilds, and differences in granivore seed preference.

Response of herbaceous layer species to canopy and soil variables in a central Appalachian hardwood forest ecosystem

Previous work has suggested that excess nitrogen (N) alters the degree to which forest canopy versus soil variables influence forest herb communities. This study tested the hypothesis that excess N would shift this influence on individual herb species from soil N availability to stand structural variables that determine light availability to the forest floor. Two watersheds at the Fernow Experimental Forest, West Virginia, USA were used: WS4 and WS3 as untreated reference and treatment watersheds, respectively. WS3 receives 35 kg N/ha/year via aerial application. Herb cover and composition was measured in seven permanent plots/WS from 1991, currently on-going. In 2011, soil moisture and N availability were measured in each plot, along with several variables of canopy structure. Backwards stepwise regression was used to determine relationships between herb cover/individual species and soil/canopy measurements. Herb cover varied spatially with soil resources on WS4, whereas cover varied spatially with canopy structure on WS3. Although results for total herb layer cover supported this hypothesis, results for individual herb species rejected it. This contrast was especially evident for Rubus allegheniensis (blackberry), a nitrophilic species which increased with increasing soil N on both watersheds, but was not correlated with canopy structure on reference WS4, while being correlated with canopy structure on N-treated WS3. Excess N from atmospheric deposition has been shown to decrease plant biodiversity of impacted forests, especially in its effects on herbaceous layer communities. This work demonstrates that one of the mechanisms of such response is in N-mediated changes in the response of herb communities to soil resources and light availability.

Traditional Lifeways and Storytelling: Tools for Adaptation and Resilience to Ecosystem Change

We collected data through three focus groups conducted with Wabanaki citizens (members of the Penobscot Nation, Passamaquoddy Tribe, Maliseet, and Micmac Nations) residing in Maine, USA, and the Canadian Maritime region. These sessions used a collective storytelling and discussion approach consistent with Wabanaki cultural practices to explore environmental knowledge, information on environmental change, and its impact on traditional lifeways (TLW) over time. Wild foods such as fiddleheads (Matteucia strutiopteris (L.) Tod.), berries such as blackberries (Rubus allegheniensis & R. Canadensis) and strawberries (Fragaria x ananasa), deer (Odocoileus virginianus Zimmerman), fish, and seafood provide not only physical nourishment, but also cultural connections through storytelling, harvesting, processing, and sharing of resources. It is this strong and multifaceted dependence on natural resources and systems that makes Wabanaki citizens particularly “vulnerable” to climate change, but also potentially resilient because of stories and other cultural traditions that help process and understand environmental change. We suggest storytelling continues to remain relevant as a way to connect the generations and for continued adaptation to ecosystem change and sustaining traditions.

Deer browsing overwhelms extended leaf phenology benefits: A test case with Rubus allegheniensis and a recalcitrant hay-scented fern layer

Plant species coexistence can be promoted by multiple tradeoffs including temporal niche separation via differences in phenology. Namely, if phenological differences afford longer leaf life-spans that confer species the opportunity to exploit light and fix carbon during periods relatively free of other competitors, then coexistence, or even competitive superiority, may arise. Phenological niche separation explanations, including the Extended Leaf Phenology (ELP) hypothesis, have garnered considerable support as a mechanistic explanation for both exotic invasive species success and maintenance of native plant species. The benefits conferred by a phenological advantage, however, can be nullified if tissue losses from browsing are coincident with this phenological window of opportunity. This study experimentally tests the role of phenological advantage and white-tailed deer (Odocoileus virginianus) browsing, alone and in concert, in structuring coexistence between the native forest shrub Rubus allegheniensis, which possesses an extended phenological window, and the native invasive fern Dennstaedtia punctilobula. Browsing treatments (ambient versus excluded) were factorially crossed with shading treatments (none versus shading timed to eliminate phenological advantage). The results demonstrate the phenological advantage is an essential growth mechanism for Rubus as seedlings deprived of the ELP advantage were, on average, 50% shorter than those not treated with shade. However, this benefit was largely dependent on herbivory pressure, as deer browsing largely nullified the growth benefits provided by the phenological advantage. This experiment is the first experimental study documenting how browsing impacts affect a plant species by curtailing a phenological coexistence advantage. The results suggest elucidating the interacting roles of the ELP and browsing is critical, particularly as the phenological niche advantage does not necessarily constitute a fitness advantage where browsing pressure is high. Results from this work also provide broader insight into how exotic plant species invasions that are assumed to be aided by a phenological (ELP) advantage, may be modulated through their browse susceptibility. Overall, these results suggest understanding the co-occurring roles of phenology and browsing may guide management decisions to maintain or promote understory plant diversity.

Discovery and exploitation of a natural ecological trap for a mosquito disease vector.

Ecological traps occur due to a mismatch between a habitat's attractiveness and quality, wherein organisms show preference for low-quality habitats over other available high-quality habitats. Our previous research identified leaf litter from common blackberry (Rubus allegheniensis) as a natural ecological trap for an important vector for West Nile virus (Culex pipiens), attracting mosquitoes to oviposit in habitats deleterious to the survival of their larvae. Here we demonstrate that manipulation of leaf litter in stormwater catch basins, an important source of disease vector mosquitoes in urban environments, can increase Cx. pipiens oviposition but reduce survival. In a series of experiments designed to elucidate the mechanisms that explain the attractive and lethal properties of this native plant, behavioural bioassays suggest that oviposition site selection by Cx. pipiens is mediated primarily by chemical cues as leaves decompose. However, we also show that juvenile mosquito survival is mainly related to the suitability of the bacterial community in the aquatic habitat for mosquito nutritional needs, which does not appear to create a cue that influences oviposition choice. This mismatch between oviposition cues and drivers of larval habitat quality may account for the ecological trap phenomenon detected in this study. Our findings provide new insights into potential mechanistic pathways by which ecological traps may occur in nature and proof-of-concept for a new 'attract-and-kill' tool for mosquito control.

Response of foliar nutrients of Rubus allegheniensis to nutrient amendments in a central Appalachian hardwood forest

Abstract Foliar nutrient concentrations are often useful in inferring soil fertility and plant-soil interactions. This study examined pre- and post-senescent foliar macronutrients and Mn of Rubus allegheniensis to assess potential effects of two nutrient amendments on mineral soil nutrient availability in aggrading hardwood stands: additions of (NH4)2SO4 (simulating increases in acid deposition) and additions of (NH4)2SO4 with dolomitic limestone (simulating mitigation of effects of acidification). Foliar Mn analysis further addressed a prediction of the nutrient redistribution hypothesis, i.e., Rubus accumulates Mn in pre-senescent leaves and further concentrates Mn in post-senescent leaves to produce high-Mn litter. The study used a four plot × four block randomized design with three experimental treatments (Control, NS, NS + Lime). Rubus leaves were harvested randomly in plots of all treatment before and after senescence. Experimental treatments appeared to increase availability of N and P, with little effect on K. Simulated acidification decreased availability of Ca and Mg, an effect mitigated for Mg by addition of dolomitic limestone. By contrast, Mn in Rubus foliage was up to 100 times more concentrated than in most plant species, and was further concentrated by ∼60% during senescence. These latter observations support predictions of the nutrient redistribution hypothesis that Rubus redistributes Mn from the rooting zone to surface soil.

Beneath it all: Size, not origin, predicts belowground competitive ability in exotic and native shrubs1,2

Abstract Traits associated with root morphology and nutrient uptake rate may contribute to the competitive ability of invasive species by determining their access to soil nutrients and their ability to extract those resources. Here, we tested the hypotheses that (a) exotic woody shrubs would be superior belowground competitors for nitrogen in heterogeneous soil resulting from key aspects of root architecture and (b) larger plants would be superior belowground competitors. We tested these hypotheses using two native shrubs, Rubus allegheniensis and Viburnum dentatum, and two invasive exotic shrubs, Rubus phoenicolasius and Berberis thunbergii, all four of which can become abundant in plant communities in the eastern United States. We grew replicate plants from each species with interspecific competitors, with intraspecific competitors, and individually in a randomized layout in a greenhouse in two temporal blocks. Each experimental container had a central soil patch amended with 15N-labeled litter. We meas...

Non-Crop Host Sampling Yields Insights into Small-Scale Population Dynamics of Drosophila suzukii (Matsumura).

Invasive, polyphagous crop pests subsist on a number of crop and non-crop resources. While knowing the full range of host species is important, a seasonal investigation into the use of non-crop plants adjacent to cropping systems provide key insights into some of the factors determining local population dynamics. This study investigated the infestation of non-crop plants by the invasive Drosophila suzukii (Matsumura), a pest of numerous economically important stone and small fruit crops, by sampling fruit-producing non-crop hosts adjacent to commercial plantings weekly from June through November in central New York over a two-year period. We found D. suzukii infestation rates (number of flies emerged/kg fruit) peaked mid-August through early September, with Rubus allegheniensis Porter and Lonicera morrowii Asa Gray showing the highest average infestation in both years. Interannual infestation patterns were similar despite a lower number of adults caught in monitoring traps the second year, suggesting D. suzukii host use may be density independent.

Effects of excess nitrogen on biogeochemistry of a temperate hardwood forest: Evidence of nutrient redistribution by a forest understory species

Excess nitrogen (N) in terrestrial ecosystems can arise from anthropogenically-increased atmospheric N deposition, a phenomenon common in eastern US forests. In spite of decreased N emissions over recent years, atmospheric concentrations of reactive N remain high in areas within this region. Excess N in forests has been shown to alter biogeochemical cycling of essential plant nutrients primarily via enhanced production and leaching of nitrate, which leads to loss of base cations from the soil. The purpose of our study was to investigate this phenomenon using a multifaceted approach to examine foliar nutrients of two herbaceous layer species in one N-treated watershed (WS3—receiving aerial applications of 35 kg N/ha/yr as ammonium sulfate, from 1989 to the present) and two untreated reference watersheds at the Fernow Experimental Forest, WV, USA. In 1993, we analyzed foliar tissue of Viola rotundifolia, a dominant herb layer species and prominent on all seven sample plots in each watershed. In 2013 and 2014, we used foliar tissue from Rubus allegheniensis, which had become the predominant species on WS3 and had increased, though to a lesser extent, in cover on both reference watersheds. Foliar N and potassium (K) were higher and foliar calcium (Ca) was lower on WS3 than on the reference watersheds for both species. Magnesium (Mg) was lower on WS3 for Viola, but was not different among watersheds for Rubus. Results support the stream chemistry-based observation that excess N lowers plant-available Ca and, to a lesser degree, Mg, but not of K. Foliar manganese (Mn) of Rubus averaged >4 times that of Viola, and was >50% higher on WS3 than on the reference watersheds. A Mn-based mechanism is proposed for the N-meditated increase in Rubus on WS3. Data suggest that excess N deposition not only alters herb community composition and biogeochemical cycling of forest ecosystems, but can do so simultaneously and interactively.

An analysis of a Hackberry–American Elm–green Ash forest type at Moser Park, Allen County, Indiana

Abstract Moser Park is a property in Allen County, Indiana, managed by New Haven Parks and Recreation. We conducted a plant survey within the forested section of the park, identifying and quantifying abundance of understory, midstory, and overstory plants. We calculated species richness and Shannon's index for all three strata and tested for relationships with environmental variables (i.e., canopy cover, soil compaction, litter depth, and light availability). The majority of understory species are typically associated with disturbed habitats, with very little resemblance to natural, pre-settlement habitat (i.e., low coefficient of conservation values). Understory cover was dominated by Rubus allegheniensis. Midstory stratum was less diverse than the understory and was dominated by an abundance of Fraxinus pennsylvanica, which was also an important species in the overstory. The forest at Moser Park matched the Hackberry–American Elm–Green Ash forest type. There was a lack of both Quercus and many Acer spec...

Asymmetric effects of native and exotic invasive shrubs on ecology of the West Nile virus vector Culex pipiens (Diptera: Culicidae).

BackgroundExotic invasive plants alter the structure and function of native ecosystems and may influence the distribution and abundance of arthropod disease vectors by modifying habitat quality. This study investigated how invasive plants alter the ecology of Culex pipiens, an important vector of West Nile virus (WNV) in northeastern and midwestern regions of the United States.MethodsField and laboratory experiments were conducted to test the hypothesis that three native leaf species (Rubus allegheniensis, blackberry; Sambucus canadensis, elderberry; and Amelanchier laevis, serviceberry), and three exotic invasive leaf species (Lonicera maackii, Amur honeysuckle; Elaeagnus umbellata, autumn olive; and Rosa multiflora, multiflora rose) alter Cx. pipiens oviposition site selection, emergence rates, development time, and adult body size. The relative abundance of seven bacterial phyla in infusions of the six leaf species also was determined using quantitative real-time polymerase chain reaction to test the hypothesis that variation in emergence, development, and oviposition site selection is correlated to differences in the diversity and abundance of bacteria associated with different leaf species, important determinants of nutrient quality and availability for mosquito larvae.ResultsLeaf detritus from invasive honeysuckle and autumn olive yielded significantly higher adult emergence rates compared to detritus from the remaining leaf species and honeysuckle alleviated the negative effects of intraspecific competition on adult emergence. Conversely, leaves of native blackberry acted as an ecological trap, generating high oviposition but low emergence rates. Variation in bacterial flora associated with different leaf species may explain this asymmetrical production of mosquitoes: emergence rates and oviposition rates were positively correlated to bacterial abundance and diversity, respectively.ConclusionsWe conclude that the displacement of native understory plant species by certain invasive shrubs may increase production of Cx. pipiens with potential negative repercussions for human and wildlife health. These findings may be relevant to mosquito control and invasive plant management practices in the geographic range of Cx. pipiens. Further, our discovery of a previously unknown ecological trap for an important vector of WNV has the potential to lead to novel alternatives to conventional insecticides in mosquito control by exploiting the apparent “attract-kill” properties of this native plant species.

Triterpenoids from the fruits and leaves of the blackberry (Rubus allegheniensis) and their inhibitory activities on foam cell formation in human monocyte-derived macrophage

From the methanol extract of the fruits of the blackberry (Rubus allegheniensis Port.), four triterpenoids – pomolic acid (1), tormentic acid (2), euscaphic acid (3) and 1β-hydroxyeuscaphic acid (4) – were isolated, while six triterpenoids – 2, 3, myrianthic acid (5), ziyu glycoside II (6), sericic acid (7) and 19-hydroxy-2,3-secours-12-ene-2,3,28-trioic acid 3-methyl ester (8) – were obtained from the methanol extract of the leaves of this plant. Their structures were determined on the basis of spectral data. Compounds 1–8 were examined for their inhibitory activities on foam cell formation in human monocyte-derived macrophages induced by acetylated low-density lipoproteins at a 50 μM concentration. Among the tested compounds, 1 showed the strongest activity, with the inhibitory effect being 90%. The inhibitory activities of 2–8 were evaluated to be 30%, 32%, 33%, 4%, 48%, 4% and 24%, respectively. Further, the structure–activity relationship of these compounds was investigated.

Gnomonia rostellata . [Descriptions of Fungi and Bacteria

Abstract A description is provided for Gnomonia rostellata . Some information on its dispersal and transmission and conservation status is given, along with details of its geographical distribution (Canada (Ontario), USA (California, North Carolina, Oregon), Austria, Belgium, Bulgaria, Czech Republic, Finland, France, Germany, Netherlands, Poland, Serbia, Spain, Sweden, Switzerland, Ukraine, UK and former Yugoslavia), hosts ( Fragaria sp., Rosa rugosa, Rosa sp., Rubus allegheniensis, Rubus caesius, Rubus fruticosus, Rubus idaeus, Rubus idaeus subsp. sachalinensis , Rubus laciniatus, Rubus parviflorus, Rubus villosus and Rubus sp.) and associated fungi ( Lophiostoma fuckelii, Otthia spiraeae and Mollisia rosae ).

Vegetation of Hooper Branch Nature Preserve, Iroquois County, Illinois

The Hooper Branch Nature Preserve is located in the extensive dune and swale topography of the sand deposits of northeastern Illinois. The plant communities present at the time of this survey were similar to those of pre-settlement times. The vegetation associated with the dunes had not been disturbed except for past grazing; the swales, in contrast, were drained and farmed before the area was dedicated in 1986. Dry and dry-mesic sand savanna was associated with the dunes where Quercus velutina (Black Oak) accounted for 75% to 97% of the importance value in the savanna. Carex pensylvanica (Pennsylvania Sedge) was the dominant ground cover species usually followed by Schizachyrium scoparium (Little Bluestem). In parts of the preserve that had been most recently burned, woody species were more common in the ground layer, with the most important being Q. velutina seedlings, Rhus copallina (Dwarf Sumac), and Rubus allegheniensis (Common Blackberry). A 3-ha flatwoods in the Preserve was dominated by Q. palustris (Pin Oak), which accounted for nearly 95% of the overstory.

The effects of disturbance intensity on temporal and spatial patterns of herb colonization in a southern New England mixed-oak forest

As managing forests for biodiversity becomes more common, it is important to understand how understory species respond to disturbance. We monitored changes in species’ dominance, calculated as importance values, over a 4-year period in order to determine how species’ dominance varied with disturbance intensity and gap position. An experimental linear canopy opening was created in a southern New England mixed-oak forest, and plots were established on the south side, center, and north side of the opening. All vegetation was removed in half of the plots, simulating a lethal disturbance. In the other half of the plots, only the overstory was removed, simulating minimal disturbance (release plot). Before the disturbance, Dennstaedtia punctilobula dominated the plots, but typical forest understory species such as Kalmia latifolia, Trientalis borealis, Maianthemum canadense, and Mitchella repens were very common. After the disturbance, D. punctilobula expanded and continued to remain dominant in all types of plots. Early successional species, such as Carex pensylvanica, Poaceae species, Rubus ideaus, and Rubus allegheniensis dominated the lethal and center plots; late successional forest understory species experienced a reduction in frequency and cover in these plots. However, in release and edge plots, late successional species maintained relatively similar frequencies and covers to pre-disturbance values. The ability of early successional species to seed into lethal plots and grow rapidly in the high light environment of the center plots allowed them to dominate in these plots. Late successional species were able to remain relatively dominant in release plots through clonal expansion and in edge plots through exclusion of early successional species from low light levels. Three years after the disturbance, most of the residual forest understory species had attained similar frequencies and covers to pre-disturbance values in all types of plots. Thus, although there is some initial loss of residual species in highly disturbed areas and in the center of the opening, most of these species are able to recover in a relatively short time period. However, locally uncommon species may be vulnerable to permanent loss. In order to minimize loss of species from the understory, forest managers should attempt to keep groundstory disturbance as minimal as possible where desirable late-successional species exist and create edge-partial shade effects with the remaining canopy for regeneration treatments.

Fruit Production in Mature and Recently Regenerated Forests of the Appalachians

ABSTRACT Fleshy fruit is a key food resource for both game and nongame wildlife, and it may be especially important for migratory birds during fall and for resident birds and mammals during winter. Land managers need to know how land uses affect the quantities and species of fruit produced in different forest types and how fruit production varies seasonally and as young stands mature. During June 1999‐April 2004, we quantified fleshy fruit abundance monthly in 31 0.1‐ha plots in 2 silvicultural treatments: 1) young 2‐age stands with low basal area retention, created by shelterwood‐with‐reserves regeneration cuts (R; harvested 1998–1999); and 2) uncut mature closed‐canopy stands (M) in 2 common southern Appalachian, USA, forest types (upland hardwood and cove hardwood [CH] forests). Over the 5‐year study period, total dry pulp biomass production was low and relatively constant in both M forest types (x̄ = 0.5‐2.0 kg/ha). In contrast, fruit production increased each year in R, and it was 5.0 to 19.6 times greater in R than in M stands beginning 3–5 years postharvest. Two disturbance‐associated species, pokeweed (Phytolacca americana) and blackberry (Rubus allegheniensis), produced a large proportion of fruit in R but showed different patterns of establishment and decline. Huckleberry (Gaylussacia ursina) recovered rapidly after harvest and was a major producer in both silvicultural treatments and forest types each year. Several herbaceous species that are not associated with disturbance produced more fruit in CHR. Few species produced more fruit in M than in R. Fruit production by most tree species was similar between R and M, due to fruiting by stump sprouts in R within 1–3 years postharvest. Fruit availability was highest during summer and early fall. American holly (Ilex opaca), sumac (Rhus spp.), and greenbriar (Smilax spp.) retained fruit during winter months but were patchy in distribution. In the southern Appalachians, young recently regenerated stands provide abundant fruit compared to mature forest stands and represent an important source of food for wildlife for several years after harvest. Fruit availability differs temporally and spatially because of differences in species composition, fruiting phenology, and the dynamic process of colonization and recovery in recently harvested stands. Land managers could enhance fruit availability for many game and nongame species by creating or maintaining young stands within forests.

Interference to Hardwood Regeneration in Northeastern North America: The Effects of Raspberries (Rubus spp.) Following Clearcutting and Shelterwood Methods

Abstract Rubus often becomes the most prominent vegetation within 2–3 years following heavy overstory disturbances at mesic sites within temperate forests of northeastern North America. This review draws together available literature about its dynamics and effects, focusing primarilyon raspberry (Rubus idaeus L.) and blackberry (Rubus allegheniensis Porter). It covers some key ecologic functions of raspberries related to nutrient leaching, microclimate near the ground, and organic matter decomposition. It also summarizes published information about the potentialinterference with desirable tree regeneration at northern hardwood sites within the region. The review concentrates on raspberry (Rubus spp.) dynamics and effects following clearcutting, shelterwood method, and other heavy overstory disturbances. Findings indicate that raspberries commonlydevelop into a dense cover after cutting and other overstory disturbances reduce the stocking of northern hardwood stands by 40% or more. Ecologically, they shade the ground, intercept and transpire water, and reduce the rate of litter decomposition and nutrient cycling, all of whichreduce leaching from a site. On poorly drained, droughty, and shallow soils, raspberries have reportedly delayed the development of hardwood regeneration. However, by 5–7 years, rapidly developing hardwood species have normally grown through the Rubus at most other sites, andthe emerging tree community has formed a closed canopy by 10–15 years. The presence of abundant, well-developed, and well-distributed advance tree regeneration ensures prompt restocking of new hardwoods, seems to minimize the potential for interference by raspberries, and precludes anyneed to release the tree seedlings from a raspberry cover. North. J. Appl. For. 23(4):288 –296.

CORRIDORS CAUSE DIFFERENTIAL SEED PREDATION

Corridors that connect disjunct populations are heavily debated in conservation, largely because the effects of corridors have rarely been evaluated by replicated, large‐scale studies. Using large‐scale experimental landscapes, we found that, in addition to documented positive effects, corridors also have negative impacts on bird‐dispersed plants by affecting seed predation, and that overall predation is a function of the seeds' primary consumer (rodents or arthropods). Both large‐seeded Prunus serotina and small‐seeded Rubus allegheniensis experienced greater predation in connected patches. However, P. serotina experienced significantly less seed predation compared to R. allegheniensis in unconnected patches, due to decreased impacts of rodent seed predators on this large‐seeded species. Viewed in light of previous evidence that corridors have beneficial impacts by increasing pollination and seed dispersal, this work demonstrates that corridors may have both positive and negative effects for the same plant species at different life stages. Moreover, these effects may differentially affect plant species within the same community: seeds primarily consumed by rodents suffer less predation in unconnected patches. By shifting the impact of rodent and arthropod seed predators, corridors constructed for plant conservation could lead to shifts in the seed bank.

DISCRIMINATION OF RUBUS CULTIVARS USING RAPD MARKERS AND PEDIGREE ANALYSIS

Few studies with random amplified polymorphic DNA (RAPD) markers have focused on blackberry genotypes. In this study we attempted to differentiate several blackberry and raspberry cultivars for genetic identification by pedigree and RAPD analyses. Rubus allegheniensis was present in 14 of 16 cultivars and had a mean genetic contribution of 15.9%. The cultivar 'Brewer' and R. argutus were also recurrent founding clones. The raspberry cultivars in this study ('Dormanred' and 'Heritage') participated as the outlier group and were identified as such in relation to the blackberry cultivars both in terms of RAPD and pedigree analysis. One hundred fifty-seven RAPD loci were used to identify 10 of 16 genotypes with unique banding patterns. Blackberries averaged 55% similarity amongst themselves, and 22% to raspberries. Overall, pedigree and RAPD data should be interpreted separately, with the RAPD data likely being more reliable.