Forest Herbs Research Articles

Inhibitory potential of naphthoquinones leached from leaves and exuded from roots of the invasive plant Impatiens glandulifera.

Exploring the effects of allelopathic plant chemicals on the growth of native vegetation is essential to understand their ecological roles and importance in exotic plant invasion. Naphthoquinones have been identified as potential growth inhibitors produced by Impatiens glandulifera, an exotic annual plant that recently invaded temperate forests in Europe. However, naphthoquinone release and inhibitory potential have not been examined. We quantified the naphthoquinone content in cotyledons, leaves, stems, and roots from plants of different ages of both the invasive I. glandulifera and native Impatiens noli-tangere as well as in soil extracts and rainwater rinsed from leaves of either plant species by using ultra-high pressure liquid chromatography-mass spectrometry (UHPLC-MS). We identified the compound 2-methoxy-1,4-naphthoquinone (2-MNQ) exclusively in plant organs of I. glandulifera, in resin bags buried into the soil of patches invaded by I. glandulifera, and in rainwater rinsed from its leaves. This indicates that 2-MNQ is released from the roots of I. glandulifera and leached from its leaves by rain. Specific bioassays using aqueous shoot and root extracts revealed a strong inhibitory effect on the germination of two native forest herbs and on the mycelium growth of three ectomycorrhiza fungi. These findings suggest that the release of 2-MNQ may contribute to the invasion success of I. glandulifera and support the novel weapons hypothesis.

Evidence for a direct negative effect of habitat fragmentation on forest herb functional diversity

The effects of habitat fragmentation on species richness and composition have been extensively studied. However, little is known about how fragmentation affects functional diversity patterns. Fragmentation can indeed affect functional diversity directly (e.g. by promoting traits associated to long-distance dispersal when fragment isolation increases) or indirectly (e.g. by decreasing species richness, hence trait diversity, when fragment area decreases). Here, we used structural equation modeling to determine whether factors associated to forest fragmentation, namely area, habitat heterogeneity, spatial isolation and age have a direct effect on forest herb functional diversity. Using occurrence data from 243 forest fragments located in northern France and six plant life-history traits, we estimated species richness and calculated functional diversity in each of these 243 forest fragments. We found that species richness was the primary driver of functional diversity in these fragments, with a strong positive and direct relationship between species richness and functional diversity. Interestingly, both fragment isolation and age had a direct negative effect on functional diversity independent of their effects on species richness. Isolation selected life-history traits associated with long-distance dispersal, while age selected for life-history traits typical of forest habitat specialists. Isolated and/or older forest fragments are thus at greater risk of local species and functional extinctions, and hence making these forest fragments particularly vulnerable to future global changes.

Effects of ecological continuity on species richness and composition in forests and woodlands: A review

Forests and woodlands with a long, uninterrupted presence (continuity) are often associated with high biodiversity and many habitat specialist species. But the mechanisms by which, and the scales in time and space at which, populations are dependent on continuity remain debated. We examine the spatial and temporal scales at which occurrences of plants, fungi, and invertebrates are affected by continuity and consider whether they are restricted by time for colonization (continuity per se) or by habitat formation times. We give improved definitions of landscape and local levels of continuity and evaluate the empirical literature with respect to these. By critically examining the reported effects of continuity on the occurrence of species in forests and woodlands, we explore the mechanisms behind the patterns at local and landscape scales. We conclude that many species are dispersal-limited in the current fragmented landscapes and occur mainly in landscapes with surplus continuity, meaning that the availability of habitats was greater in the past than it is currently. Our review indicates that local continuity per se is important at least for many forest herbs and for certain species of epiphytic lichens, insects, and land snails, but to a lesser extent for fungi. Several studies show that landscape-level continuity affects the current occurrence of species, in particular for vascular plants, but also for particular lichen, bryophyte, and invertebrate species. For continuity-dependent species, a successful conservation strategy should include both extending the period of habitat duration in relict patches and promoting habitat formation in the immediate surroundings of potential source patches. Conservation strategies need to acknowledge the continuity dependence of many species. Research on how to shorten habitat formation times by forest restoration is an urgent priority.

When beech strikes back: How strict nature conservation reduces herb-layer diversity and productivity in Central European deciduous forests

Current nature conservation policy is going to alter the tree-layer composition of many Central European deciduous forests. As a consequence of ceasing silvicultural management, the competitive ecosystem engineer European beech (Fagus sylvatica L.) will spread and the proportion of secondary tree species will considerably decrease. Thus, changes can also be expected in herb-layer diversity, productivity and composition. To predict these changes, we analysed relationships between tree- and herb-layer diversity and composition along tree-diversity gradients in the Central German woodland areas of the Hainich National Park (unmanaged) and the Göttinger Wald (managed by close-to-nature forestry).The flora of both study areas was dominated by typical forest species. In the Hainich, the herb-layer vegetation in beech-dominated stands was less diverse compared to stands richer in canopy species. Herb-layer productivity was also lower in beech-dominated stands. In the Göttinger Wald, herb-layer diversity and productivity were not related to tree-layer diversity and beech proportion, instead to the light transmissibility of the canopy layer. The different results can be explained by logging effects in the Göttinger Wald, which promoted the light factor as significant for herb-layer diversity and productivity. In the consistently darker stands of the Hainich, soil variables, particularly influenced by the ecosystem engineer beech, were decisive. Areas of high canopy diversity in the Hainich result from former management practices and can, in the future, be expected to decrease with the spread of beech.We conclude that forest management cessation will result in decreasing herb-layer diversity and productivity in many Central European deciduous woodlands, especially in landscapes where historical management practices led to unnaturally low proportions of beech. The short-term consequence of management cessation is a loss of herb-layer diversity due to reduced light availability; in the long-term, herb-layer diversity is expected to decrease due to the expansion of beech.If the key aim of nature conservation policy is to preserve and develop the typical diversity of near-natural beech forests, then a complete cessation of forest management can be advised. However, if the typical forest herb diversity of the semi-natural, century-old cultural landscape is to be maintained, close-to-nature forestry management is necessary.

Do forest plants conform to the theory of island biogeography: the case study of bog islands

Biodiversity conservation is confronted with increasing risk of extinction in isolated small-area remnants and the limitation of species to colonize recently formed habitats. We hypothesized that the equilibrium pattern of forest herb layer in long-term fragmented landscape should comply with the theory of island biogeography. Forests on mineral soil islands located in large mires of western Estonia were considered as dispersal target habitats, and forests on mainland and peninsulas in mires as sources. Species richness was the lowest in mainland forests and the effect was confounded by habitat structure, suggesting a negative effect of silvicultural management in easily accessible forests. We observed the ‘small island effect’, i.e. greater overall species richness in small-area habitats, which was determined by the habitat preference of shade tolerant generalists. The average species richness of common mainland forest specialists varied little, but capitalizing on the traditional approach and analyzing only island data, weak effects of distance and habitat quality were detected. At single species level, unexpectedly, many habitat specialists were observed to have successfully dispersed to islands, indicating insufficient knowledge of the long-distance dispersal mechanisms of forest-dwelling plants. In fragmented forest landscapes the theory of island biogeography can be applied to habitat specialist plant species, but only regarding the effect of isolation and in conditions of persistent forest structural quality. In the light of global changes, optimized conservation planning should primarily target on (i) the conservation of ancient habitat fragments independent of their current area, and (ii) the promotion of diversity of potential dispersal vectors in the landscape.

Temporal change in the herbaceous understory community of an old-growth forest: from seasons to decades

Studies focusing on the herbaceous groundlayer of forest communities have become increasingly common in the literature, yet rarely do these studies adequately capture the temporal dynamics that typify this stratum. Using long-term data from an old-growth remnant stand in southeastern Ohio, we compare seasonal, annual, and decadal changes in herb composition and abundance on a north- and south-facing slope. Herbs were sampled within 70, 2-m2 circular plots at three times throughout the growing season in 1997, 1998, 2011, and 2012. Slope, season, and year all had significant effects on species composition, as did their interactions. Species richness and diversity varied considerably throughout seasons, yet remained consistent over the fifteen-year study interval. A dramatic reduction in overall abundance, from an average of 63 % in 1997 to just 12 % in 2012, was observed. This decline was most severe from 1997 to 1998. A nonmetric multidimensional scaling ordination for all 4 years showed a collapse in phenological distinction among seasonal-sampling units. Finally, we looked at year-to-year changes in individual species abundances by comparing occurrence frequencies. The frequency of a species in year i was usually a good indicator of its frequency in year j; however, a few species showed considerable increases or decreases, such as the invasive Alliaria petiolata, which increased from zero plots in 1997 to 15 plots in 2012. These results suggest the importance of adequately and simultaneously documenting vegetation changes at short, intermediate, and long-term timescales—especially for understanding the dynamics of temperate deciduous forest herb communities.

Ecodiagrams of common species of the forest herb layer in the Roztocze National Park

The paper presents in graphic standardised form ("ecodiagrams") the conditions in which 24 common species of the herb layer of forest communities occur in the Roztocze National Park. After determining the soil type, its mechanical composition, active and exchangeable acidity, humus content and the content in the rhizosphere layer of nutrient components essential for plants, such as P, K, Na, Ca. Mg. AI, ammonium nitrogen and nitrate nitrogen, the habitats of common plants of the forest from the class <em>Querco-Fagetea</em> were classified as meso-, eu-meso- and cutrophic. Forest plants connected with communities from the class <em>Vaccinio-Piceetea (Hierncium lachenalii</em> Gmel., <em>Melampyrum pratense</em> L., <em>Trientalis eurnpaea</em> L., <em>Vaccinium myrtillus</em> L.) are generally associated with fresh, moderately poor and quite frequently also mesotrophic soils. Only <em>Vaccinium vitis-idaea</em> L. is a local species of dry hungry soils, poor in mineral and organic components. The group of accompanying species such as <em>Fragaria vesca</em> L., <em>Galium vernum</em> Scop., <em>Luzula pilosa</em> (L.) Willd., <em>Mycelis ruralis</em> (L.) Dum. and <em>Oxalis ucetosella</em> L.. show a much wider ecological amplitude-from oligotrophic to eutrophic habitats.

Tree species determine the colonisation success of forest herbs in post-agricultural forests: Results from a 9 yr introduction experiment

The limited dispersal and recruitment of ancient forest plant species (AFS) hampers the restoration of herb layer communities in post-agricultural forests. Recruitment limitation is often caused by the high availability of soil nutrients, in particular phosphorous (P), which can aggravate competitive exclusion of AFS by nutrient-demanding species. We monitored the survival, growth and reproduction of six AFS with variable ecological amplitudes for light and soil acidity according to expert-based indicator values. These AFS were introduced under eight tree species that have created specific levels of light and soil acidity within 30years after plantation on farmland. Acidifying tree species severely limited the survival of all introduced AFS except Hyacinthoides non-scripta. We observed the highest survival of AFS in moderately shaded stands and the best growth of AFS in stands with a low light level. Temporary canopy gaps promoted the survival of AFS, but also provoked dominance by light-demanding competitors before canopy closed again. The two hemicryptophyte AFS, Primula elatior and Oxalis acetosella, increased by means of sexual reproduction, while the geophytes (Anemone nemorosa, Mercurialis perennis, Pteridium aquilinum, and Hyacinthoides non-scripta), mainly expanded vegetatively. As a conclusion, we advise managers that aim to restore a species-rich forest herb layer in post-agricultural forest, not to promote strongly acidifying tree species. The regulation of the level and/or frequency of stress, soil acidity and shade in this case, can be used as a management tool to mitigate the competitive exclusion promoted by P eutrophication.

The effect of temperature and humidity changes on insects development their impact on forest ecosystems in the expected climate change

Abstract Ongoing climate change is mainly evident as increased in average temperature. It is expected to have a significant impact on world’s biomes, with forest ecosystems especially vulnerable to these changes. The effect of climate change on forests is both indirect, through its impact on various tree species of different ecological requirements, and direct, through its impact on all living components of the forest ecosystem. Among the latter, insects are the group of the greatest importance, including species detrimental to forest health. The impact of climate change on forest insects may be reflected in their distribution, phenology, activity, number of generations and, indirectly, through impact on their natural enemies. Predicting the future direction and pace of the climate change, as well as direct and indirect consequences of its effect on forest insects is difficult and often subject to considerable inaccuracy. The paper presents a review of data from the published literature in this area of study. The influence of the basic climate parameters, temperature and humidity, on forest herbivore insects is discussed, particularly in the context of the most probable scenarios of climate change, i.e. the gradual increase in the average temperature. Observed and projected impacts of climate change in relation to the influence of herbivorous insects on forest ecosystems are characterized. We present some of the possible adaptation strategies of forest management to the expected climate changes.

Forest herb layer response to long-term light deficit along a forest developmental series

Temperate deciduous forest communities are slow-changing systems, with herbaceous understorey communities displaying a delayed response to overstorey canopy and light dynamics. While light availability constrains herbaceous understorey diversity and composition in space and time, its response in the long-term absence of light has seldom been quantified, particularly as it is often confounded by covariation in soil conditions. We studied a developmental high-forest series in two widespread NW-European temperate deciduous forest communities with different dominant canopy tree species: Stellario-Carpinetum (Oak-hornbeam canopy) and Milio-Fagetum (Beech canopy). All plots had soil conditions which were not significantly different, enabling investigation into the direct effects of the long-term absence of light on the herbaceous understorey, disentangled from the confounding effects of soil variation.Plant species richness measures declined with canopy cover continuity in the herb layer of the oak-hornbeam stands, whereas richness in the herb layer of the beech stands displayed a unimodal response. Nonetheless, in both plant communities, species richness and closed-forest species richness were negatively affected by the extended absence of light in stands with the longest period of continuous canopy cover. The long-term limitation or decline in quantitative and qualitative light availability as a result of extended periods of canopy cover was shown to be the primary driver behind losses in alpha-diversity, community composition turn-over and individual species dynamics. Heliophilous species were lost from both communities, while closed-forest species also declined, as a direct consequence of the prolonged period without ample light on the forest floor. This study demonstrates how the herb layer is affected by the absence of light on the forest floor mediated by long periods of continuous canopy cover. Despite different temporal responses in herb layer richness and composition between different shade-casting canopy species, the eventual outcome in the prolonged absence of light is independent of dominant canopy species.

Hybrid poplar plantations are suitable habitat for reintroduced forest herbs with conservation status

Plantations of fast-growing tree species may be of use in conservation by accelerating the restoration of forest habitat on abandoned farmland and increasing connectivity in fragmented landscapes. The objective of this study was to determine if hybrid poplar plantations can be suitable habitats for the reintroduction of native forest plant species and, if so, which abiotic factors predict successful reintroduction. Four species of forest herb species (Trillium grandiflorum, Sanguinaria canadensis, Maianthemum racemosum, Asarum canadense), of which three have legal conservation status, were transplanted into experimental plantations of two hybrid poplar clones and nearby second-growth woodlots at six sites in southern Quebec, Canada. The transplanted individuals were protected from deer browsing with exclusion cages. After two years, the plant responses of all four species were stable or increased over two years in both types of hybrid poplar plantations. Sanguinaria showed a better response in the plantations than in the woodlots, preferring the rich post-agricultural soils of the plantations with low C:N ratios. Asarum and Maianthemum showed no significant difference between stand types, while Trillium grew better in the woodlots than in the plantations. Much of the variability in the response of the latter three species was unexplained by the measured environmental variables. These results suggest that certain forest herb species can be reintroduced as juvenile plants into plantations, knowing that their spontaneous recolonization is often limited by dispersal and/or seedling establishment. Plantations could also contribute to the conservation of biodiversity by providing an environment for the cultivation of forest herb species as an alternative to their destructive harvest from natural populations.

Reassessment of the Use of Fire as a Management Tool in Deciduous Forests of Eastern North America

Prescribed burning is increasingly being used in the deciduous forests of eastern North America. Recent work suggests that historical fire frequency has been overestimated east of the prairie-woodland transition zone, and its introduction could potentially reduce forest herb and shrub diversity. Fire-history recreations derived from sedimentary charcoal, tree fire scars, and estimates of Native American burning suggest point-return times ranging from 5-10 years to centuries and millennia. Actual return times were probably longer because such records suffer from selective sampling, small sample sizes, and a probable publication bias toward frequent fire. Archeological evidence shows the environmental effect of fire could be severe in the immediate neighborhood of a Native American village. Population density appears to have been low through most of the Holocene, however, and villages were strongly clustered at a regional scale. Thus, it appears that the majority of forests of the eastern United States were little affected by burning before European settlement. Use of prescribed burning assumes that most forest species are tolerant of fire and that burning will have only a minimal effect on diversity. However, common adaptations such as serotiny, epicormic sprouting, resprouting from rhizomes, and smoke-cued germination are unknown across most of the deciduous region. Experimental studies of burning show vegetation responses similar to other forms of disturbance that remove stems and litter and do not necessarily imply adaptation to fire. The general lack of adaptation could potentially cause a reduction in diversity if burning were introduced. These observations suggest a need for a fine-grained examination of fire history with systematic sampling in which all subregions, landscape positions, and community types are represented. Responses to burning need to be examined in noncommercial and nonwoody species in rigorous manipulative experiments. Until such information is available, it seems prudent to limit the use of prescribed burning east of the prairie-woodland transition zone.

Contrasting effects of different landscape characteristics on population growth of a perennial forest herb

Anthropogenic changes in landscape structure, such as habitat loss, habitat subdivision and edge increase, can strongly affect the performance of plants, leading to population declines and extinctions. Many studies to date have focused on single characteristics of landscape structure or single life‐cycle phases, but they poorly discern the different pathways through which landscape change influences plant population dynamics via different vital rates. In this study, we evaluated the effect of two structural characteristics (habitat quantity and edge length) on vital rates and population growth rates of a perennial forest plant (Primula vulgaris) in a historically managed landscape. Areas with higher amounts of forest habitat had higher population growth rates due to higher recruitment, survival and growth of seedlings, while increased forest edge length was positively associated with population growth rates primarily due to a higher survival of reproductive individuals. Effects were stronger during the first of the two transition intervals studied. The results demonstrate that changes in different landscape structural characteristics may result in opposing effects acting via different vital rates, and highlight the need for integrative analyses to evaluate the effects of rapid landscape transformation on the current and long term plant population dynamics.

Streams are efficient corridors for plant species in forest metacommunities

Summary The maintenance, restoration or construction of corridors are among the most important conservation strategies world‐wide in the face of global changes such as habitat fragmentation and climate change, although their effectiveness still remains an open question. Metacommunity ecology provides a useful framework to answer this question but so far relatively few studies have concerned plant species. Here, we evaluate the connectivity effect of small streams originating in a large forest for plant communities of forest patches within an agricultural landscape. We compared α‐ and β‐diversity of patches connected to a large forest with isolated patches whilst controlling for habitat effects and patch area. Species composition of each patch type was examined with a nonparametric MANOVA and an indicator species analysis. We found that forest patches connected to the main forest through streams were not more species rich after accounting for habitat effects but were more similar than isolated patches, be the latter crossed or not by a stream. Connected patches exhibited a different species composition with more forest habitat specialists and more hydrochores than nonconnected patches. Many forest herb species well known for being dispersal‐limited appeared to be efficiently transported by water as incidental hydrochores over long distances and relatively short‐time scales. Using streams as ‘high‐speed corridors’, these species increased their colonization speed by at least 15 times compared with conventional dispersal. Synthesis and applications. This study demonstrates that streams can act as efficient corridors for plant species across agricultural landscapes and contribute to the dynamics of forest metacommunities. From a management perspective, preserving the longitudinal integrity of streams is likely to increase the connectivity within and between forest metacommunities and can assist dispersal‐limited species to be resilient to projected climate warming by increasing their migration speed. Restoring not only wooded elements but watercourse networks is thus a suitable strategy to manage landscapes efficiently for the forest flora conservation.

Performance and population dynamics of a native understory herb differ between young and old forest stands in the Southern Appalachians

Anthropogenic disturbances (e.g., logging) can strongly affect the composition and structure of forest understory herb communities, with land-use legacies often persisting for decades or even centuries. Many studies of forest plant response to land-use history have focused on species distributions and abundances, and argued broadly for either dispersal or establishment limitation as biological mechanisms for slow recolonization. We asked how performance and population dynamics of the temperate forest herb Prosartes lanuginosa differed between recently logged (20–40years ago) and old (>90years) logged forests in the Southern Appalachians, USA. All stands were well developed with canopy closure ranging from 59–90%. Performance of individual plants (N=859) was monitored over three years across 19 forest stands (N=9 recent and 10 old). We also conducted a seed sowing experiment to determine whether germination and establishment differed with stand age. Stage-based matrix models and life table response experiments (LTREs) were used to quantify the contributions of each life-history transition to observed differences in population growth rates (λ) across stands and between years. Field measurements revealed that population growth rates were higher in older logged stands (λ=0.78–0.84) than in more recently logged stands (λ=0.68–0.74), primarily because of reduced fecundity and reduced recruitment from vegetative to flowering life stages. Seed germination and seedling survival did not differ between old and young logged forests. Across stands, population growth rates were higher during the first annual transition than the second, which followed a drought spring. However, the mechanisms for these differences in λ varied with stand age; populations in old forests responded to drought conditions by lowering fecundity, whereas populations in young forests responded with lower recruitment from vegetative to flowering stages. Our results showed that logging history affects plant performance beyond the establishment phase and interacts with environmental conditions to influence population dynamics. Our results also emphasize the need for multiple performance measures to assess the effects of land-use history on forest plants.

Can soil acidity and light help to explain tree species effects on forest herb layer performance in post-agricultural forests?

Aims Tree species affect herb layer species through their effects on soil quality and light regime but their relative importance and interactions are insufficiently known.

Climatic control of forest herb seed banks along a latitudinal gradient

AbstractAimSeed banks are central to the regeneration strategy of many plant species. Any factor altering seed bank density thus affects plant regeneration and population dynamics. Although seed banks are dynamic entities controlled by multiple environmental drivers, climatic factors are the most comprehensive, but still poorly understood. This study investigates how climatic variation structures seed production and resulting seed bank patterns.LocationTemperate forests along a 1900 km latitudinal gradient in north‐western (NW) Europe.MethodsSeed production and seed bank density were quantified in 153 plots along the gradient for four forest herbs with different seed longevity: Geum urbanum, Milium effusum, Poa nemoralis and Stachys sylvatica. We tested the importance of climatic and local environmental factors in shaping seed production and seed bank density.ResultsSeed production was determined by population size, and not by climatic factors. G. urbanum and M. effusum seed bank density declined with decreasing temperature (growing degree days) and/or increasing temperature range (maximum–minimum temperature). P. nemoralis and S. sylvatica seed bank density were limited by population size and not by climatic variables. Seed bank density was also influenced by other, local environmental factors such as soil pH or light availability. Different seed bank patterns emerged due to differential seed longevities. Species with long‐lived seeds maintained constant seed bank densities by counteracting the reduced chance of regular years with high seed production at colder northern latitudes.Main conclusionsSeed bank patterns show clear interspecific variation in response to climate across the distribution range. Not all seed banking species may be as well equipped to buffer climate change via their seed bank, notably in short‐term persistent species. Since the buffering capacity of seed banks is key to species persistence, these results provide crucial information to advance climatic change predictions on range shifts, community and biodiversity responses.

Plant–animal interactions in two forest herbs along a tree and herb diversity gradient

Background: Plant diversity can influence numerous ecosystem processes, including plant–animal interactions, which, in turn, will affect plant growth and fitness. At present, little is known on how plant–animal interactions in forests respond to gradients in tree and herb-layer diversity. Aims: To quantify how invertebrate herbivory, pollination-dependent seed production and post-dispersal seed predation vary along a gradient of tree and herb diversity in a semi-natural temperate deciduous forest. Methods: Potted individuals of the understorey herbs Lathyrus vernus and Primula elatior were exposed in 40 forest plots along a natural gradient of tree and herb diversity for 3 months to record seed production and leaf damage caused by invertebrate herbivores. In half the plants, pollinators were experimentally excluded to test if seed production depended on insect pollination. In Lathyrus vernus linkages between below- and above-ground herbivory were tested by inoculating plants with root-feeding nematodes. To study seed predation, we measured seed removal from seed depots that were selectively accessible to different seed predator groups. Results: Herbivore damage decreased with increasing tree diversity in P. elatior. In L. vernus, above-ground herbivory was higher in nematode-treated plants than in control plants. Seed production in L. vernus, which strongly depended on insect pollination, showed a positive relationship with tree diversity. Seed predation was positively related to herb diversity in L. vernus, but only weakly so in P. elatior. While both vertebrates and invertebrates acted as seed predators of L. vernus, seeds of P. elatior were mainly predated by invertebrates. Conclusions: The fitness of understorey plants is linked to tree and herb diversity via changes in plant-invertebrate interactions. However, species-specific responses of study plants underline the importance of species identity effects in addition to effects of biodiversity per se.

Among-Population Variation in Microbial Community Structure in the Floral Nectar of the Bee-Pollinated Forest Herb Pulmonaria officinalis L

BackgroundMicrobial communities in floral nectar have been shown to be characterized by low levels of species diversity, yet little is known about among-plant population variation in microbial community composition.Methodology/Principal FindingsWe investigated the microbial community structure (yeasts and bacteria) in floral nectar of ten fragmented populations of the bee-pollinated forest herb Pulmonaria officinalis. We also explored possible relationships between plant population size and microbial diversity in nectar, and related microbial community composition to the distance separating plant populations. Culturable bacteria and yeasts occurring in the floral nectar of a total of 100 plant individuals were isolated and identified by partially sequencing the 16S rRNA gene and D1/D2 domains of the 26S rRNA gene, respectively. A total of 9 and 11 yeast and 28 and 39 bacterial OTUs was found, taking into account a 3% (OTU0.03) and 1% sequence dissimilarity cut-off (OTU0.01). OTU richness at the plant population level (i.e. the number of OTUs per population) was low for yeasts (mean: 1.7, range: 0–4 OTUs0.01/0.03 per population), whereas on average 6.9 (range: 2–13) OTUs0.03 and 7.9 (range 2–16) OTUs0.01 per population were found for bacteria. Both for yeasts and bacteria, OTU richness was not significantly related to plant population size. Similarity in community composition among populations was low (average Jaccard index: 0.14), and did not decline with increasing distance between populations.Conclusions/SignificanceWe found low similarity in microbial community structure among populations, suggesting that the assembly of nectar microbiota is to a large extent context-dependent. Although the precise factors that affect variation in microbial community structure in floral nectar require further study, our results indicate that both local and regional processes may contribute to among-population variation in microbial community structure in nectar.

Oxynetra: Facies and DNA Barcodes Point to a New Species from Costa Rica (Hesperiidae: Pyrginae: Pyrrhopygini)

Oxynetra stangelandi Grishin & Burns, new species, from high elevations of Area de Conservacion Guanacaste (ACG) in northwestern Costa Rica, is most similar to Oxynetra hopfferi Staudinger, known from mountains of central and southern Costa Rica and western Panama. These hesperiid species differ mainly in body color pattern and in DNA barcodes. We compare their barcodes, nucleotide by nucleotide, together with barcodes of a congener and a species of the related genus Olafia, and use the barcode data to show phylogenetic relationships. We describe the new species, its discovery, its male and female genitalia, and its life history as a cloud forest herbivore of Prunus annularis (Rosaceae). In ACG, no other skippers feed on this plant species, and no other skippers of the tribe Pyrrhopygini feed on plants in the family Rosaceae. Various stages of O. stangelandi belong to mimicry complexes. Although our adults, which are reared from wild-caught caterpillars, are split between the sexes (4 males, 6 females), there are scarcely any females of Oxynetra in the world's museums.