Partitioning of soil phosphorus regulates competition between Vaccinium vitis‐idaea and Deschampsia cespitosa

It has been hypothesized that the wide range of forms and complexities of phosphorus (P) in soil may result in resource partitioning that contributes to the maintenance of plant species diversity. Here, we test whether the graminoid, Deschampsia cespitosa, and the ericaceous shrub, Vaccinium vitis‐idaea, which often coexist, display preferences in utilization of P forms, and differ in their production of extracellular P‐degrading enzymes. We provided plants with no additional P, or P forms with decreasing lability, namely sodium phosphate (SP), D‐glucose 6 phosphate (DG6P), sodium phytate (PASS), and a combination of SP, DG6P, and PASS. We also tested if preferences for P forms affected the competitive outcomes between the two species compared between conspecifics, as indicated by shoot biomass and acquisition of nitrogen (N) and P. Both D. cespitosa and V. vitis‐idaea produced the greatest biomass when supplied with a mix of all three forms of P. Of the three forms of P tested alone, shoot biomass produced by both species was least when supplied with SP. D. cespitosa performed better when grown with PASS or a mix of all P forms compared with the performance of V. vitis‐idaea on these substrates. This was reflected by substantially greater phytase activity on the surface of its roots compared with V. vitis‐idaea. In contrast, V. vitis‐idaea produced more phosphomonoesterase to hydrolyze the simple organic P form, DG6P. Although N was kept constant in the treatments, the ability of plants to acquire it was dependent on species identity, competition, and P supply. These findings provide direct evidence for preferences toward specific forms of P and indicate a key role played by organic forms of P. The results support the idea that partitioning for soil P is one factor regulating plant competition, and ultimately, community composition. Our data also highlight the importance of the interplay between P supply and N acquisition.     

Water- and nutrient-use efficiency of a deciduous species, Vaccinium myrtillus, and an evergreen species, V. vitis-idaea, in a subalpine dwarf shrub heath in the southern Alps, Italy

Periodic measurements of gas‐exchange rates and determinations of foliar N and P concentrations were used for evaluating instantaneous water‐use efficiency and photosynthetic nutrient‐use efficiency in two co‐existing dwarf shrubs of different growth form (V. myrtillus, deciduous, and V. vitis‐idaea, evergreen) in a subalpine heath in the southern Alps of Italy. Those data were compared with cumulative assessments of water‐use efficiency and photosynthetic nutrient‐use efficiency obtained by measuring leaf carbon isotope discrimination in leaf tissues and by estimating nutrient resorption from senescing leaves. V. myrtillus presented higher dry‐weight based rates of net photosynthesis (A_weight) compared to V. vitis‐idaea. A_weight was positively correlated with foliar‐nutrient status and intercellular‐to‐ambient gradient in CO₂ concentrations. A_weight was, furthermore, negatively correlated with leaf specific mass. Instantaneous photosynthetic nutrient‐use efficiency did not differ between the two species but the percentages of N and P pools resorbed from senescing leaves were somewhat higher in the deciduous species. The evergreen species showed lower P concentrations in senescing leaves which indicated a higher proficiency in resorbing phosphorus compared to the deciduous species. In addition, the evergreen species achieved a higher carbon gain per unit foliar N and P, due to a longer mean residence time of both nutrients. The two species did not differ from each other with respect to both instantaneous and long‐term water‐use efficiency. This was consistent with the climatic pattern, showing no sign of water deficiency through the growing season. Current‐year V. vitis‐idaea leaves had a significantly higher Δ¹³C compared to previous‐year leaves, possibly mirroring a long term acclimation of evergreen leaves, as far as they age, to the habitat conditions in the understory where evergreen species are usually confined within mixed dwarf‐shrub communities.     

Responses to harvesting intensity in a clonal dwarf shrub,the bilberry (Vaccinium myrtillus L.)

The effects of herbivory were simulated on stands of bilberry (Vaccinium myrtillus L.) in a boreal Empetrum-Myrtillus type forest. Five harvesting intensities were used (0% (A), 25% (B), 50% (C), 100% (D) of the bilberry ramets or all the ramets of all species (E)). Density and biomass of the stands, and growth of the ramets were monitored for five growth seasons, from 1986 to 1990. After damage new ramets emerged rapidly from dormant buds at the base of removed ramets. Between 70 and 97% of the density relative to the control level was regained by the final harvest. However, only between 11 and 64% of the biomass relative to the control level was recovered. Clipping reduced the branch growth, both in the new ramets and in the new parts of the old, unclipped ramets. Severe treatments (D and E) decreased the growth more than did light harvesting (B and C). Survival and fecundity of the ramets were not affected. The result therefore suggested that the bilberry is not able to recover totally from severe herbivory damage between the years of peak rodent population that shows a 3–4 year cycle. Nevertheless, extreme grazing pressure is rare in boreal ecosystems as alternative food is available for herbivores, and predators also limit the herbivore population. Hence the bilberry exhibits moderate tolerance of the usual level of herbivory damage.     

Syntaxonomy and chorology of the Vaccinium myrtillus communities in the Monti Reatini (Central Italy)

Abstract

The present paper details the results of a phytosociological study on Vaccinium myrtillus communities in the Monti Reatini (Central Apennines). A comparison is reported with Vaccinium communities from the rest of the Italian peninsula (already described), showing the coenological and syntaxonomical autonomy of the Monti Reatini types. The Authors include the Monti Reatini shrublands with V. myrtillus and Juniperus nana in the Pino-Juniperetea class and secondary vegetation forms dynamically linked to them in two new Poo violaceae-Nardetum subassociations: Poo violaceae-Nardetum brachypodietosum rupestris and Poo violaceae-Nardetum caricetosum kitaibelianae.     

Predicting biomass of bilberry (Vaccinium myrtillus) using rank distribution and root-to-shoot ratio models

Plant Ecology - Investigation of relationships between biomass of different plant compartments is important because their varying turnover rates affect the amount and composition of aboveground and...     

Phylogeography of two European Reticulitermes (Isoptera) species: the Iberian refugium

Chemical, i.e. cuticular hydrocarbons, and molecular data were used to probe the phylogeography of Reticulitermes termites collected from various parts of France, Spain and Portugal. Phylogenetic relationships were inferred from sequences of the internal transcribed spacer (ITS2) of nuclear ribosomal RNA genes as well as from two partial mitochondrial DNA segments, the cytochrome oxidase II gene and a sequence combining the tRNA-Leu gene and fragments of the NADH dehydrogenase I and ribosomal 16S genes. Two species, namely, R. grassei and R. banyulensis, were identified based on an analysis of cuticular hydrocarbons and the identification was confirmed by ITS2 haplotyping. However, phylogeny based on the analysis of mitochondrial DNA was not completely in agreement with the conclusions drawn from the chemical and nuclear data. An analysis of 56 R. grassei colonies revealed intraspecific differentiation into two major lineages with distinct geographical ranges. Whereas analysis of cuticular hydrocarbons showed that R. banyulensis was chemically distinct from R. grassei, analysis of mitochondrial DNA showed its close kinship with the R. grassei lineage occurring in southern Spain. This kinship could be explained by their evolution from a common polymorphic ancestor species in this ice age refugium.     

Evolution of a hybrid zone of two willow species (Salix L.) in the European Alps analyzed by RAD‐seq and morphometrics

Natural hybridization of plants can result in many outcomes with several evolutionary consequences, such as hybrid speciation and introgression. Natural hybrid zones can arise in mountain systems as a result of fluctuating climate during the exchange of glacial and interglacial periods, where species retract and expand their territories, resulting in secondary contacts. Willows are a large genus of woody plants with an immense capability of interspecific crossing. In this study, the sympatric area of two diploid sister species, S. foetida and S. waldsteiniana in the eastern European Alps, was investigated to study the genomic structure of populations within and outside their contact zone and to analyze congruence of morphological phenotypes with genetic data. Eleven populations of the two species were sampled across the Alps and examined using phylogenetic network and population genetic structure analyses of RAD Seq data and morphometric analyses of leaves. The results showed that a homoploid hybrid zone between the two species was established within their sympatric area. Patterns of genetic admixture in homoploid hybrids indicated introgression with asymmetric backcrossing to not only one of the parental species but also one hybrid population forming a separate lineage. The lack of F1 hybrids indicated a long‐term persistence of the hybrid populations. Insignificant isolation by distance suggests that gene flow can act over large geographical scales. Morphometric characteristics of hybrids supported the molecular data and clearly separated populations of the parental species, but showed intermediacy in the hybrid zone populations with a bias toward S. waldsteiniana. The homoploid hybrid zone might have been established via secondary contact hybridization, and its establishment was fostered by the low genetic divergence of parental species and a lack of strong intrinsic crossing barriers. Incomplete ecological separation and the ability of long‐distance dispersal of willows could have contributed to the spatial expansion of the hybrid zone.     

Comparison of two methods used to analyse lipid peroxidation from Vaccinium myrtillus (L.) during snow removal, reacclimation and cold acclimation.

Malondialdehyde (MDA) concentration is a widely used method to analyse lipid peroxidation in biological material. In plant tissues, however, certain compounds (anthocyanins, carbohydrates) may interfere with measurements which may lead to an overestimation of the MDA levels. Two methods were compared for analysing lipid peroxidation, either uncorrected or corrected for interfering compounds. The comparison was performed in three separate experiments with respect to cold treatments (snow removal in winter, reacclimation in summer and cold acclimation in autumn) in bilberry (Vaccinium myrtillus L.). During winter and autumn the methods seem to measure different compounds, but during active growth in the summer the difference between the methods was less. This is obviously due to carbohydrates which act as cryoprotectants and increase in concentration during cold acclimation as well as due to the anthocyanins. It is thus suggested that the validity of the uncorrected method to measure MDA and thereby lipid peroxidation is best in plant tissue which is in an active growth state.     

Water–energy,land‐cover and heterogeneity drivers of the distribution of plant species richness in a mountain region of the European Alps

Aim To evaluate the relative importance of water–energy, land‐cover, environmental heterogeneity and spatial variables on the regional distribution of Red‐Listed and common vascular plant species richness. Location Trento Province (c. 6200 km²) on the southern border of the European Alps (Italy), subdivided regularly into 228 3′ × 5′ quadrants. Methods Data from a floristic inventory were separated into two subsets, representing Red‐Listed and common (i.e. all except Red‐Listed) plant species richness. Both subsets were separately related to water–energy, land‐cover and environmental heterogeneity variables. We simultaneously applied ordinary least squares regression with variation partitioning and hierarchical partitioning, attempting to identify the most important factors controlling species richness. We combined the analysis of environmental variables with a trend surface analysis and a spatial autocorrelation analysis. Results At the regional scale, plant species richness of both Red‐Listed and common species was primarily related to energy availability and land cover, whereas environmental heterogeneity had a lesser effect. The greatest number of species of both subsets was found in quadrants with the largest energy availability and the greatest degree of urbanization. These findings suggest that the elevation range within our study region imposes an energy‐driven control on the distribution of species richness, which resembles that of the broader latitude gradient. Overall, the two species subsets had similar trends concerning the relative importance of water–energy, land cover and environmental heterogeneity, showing a few differences regarding the selection of some predictors of secondary importance. The incorporation of spatial variables did not improve the explanatory power of the environmental models and the high original spatial autocorrelation in the response variables was reduced drastically by including the selected environmental variables. Main conclusions Water–energy and land cover showed significant pure effects in explaining plant species richness, indicating that climate and land cover should both be included as explanatory variables in modelling species richness in human‐affected landscapes. However, the high degree of shared variation between the two groups made the relative effects difficult to separate. The relatively low range of variation in the environmental heterogeneity variables within our sampling domain might have caused the low importance of this complex factor.     

Genetic diversity and phylogenetic relationships of the endangered species Vaccinium sieboldii and Vaccinium ciliatum (Ericaceae)

The edible berry species Vaccinium sieboldii, Vaccinium ciliatum, and Vaccinium oldhami are deciduous shrubs found growing at low altitudes in Japan. They are classified in the same section. Of these, the former two species are listed as endangered species. The present status of these two species was surveyed. V. sieboldii was found in a very limited range, 65 km wide, in central Japan. Many plants are thought to have been lost because of habitat destruction in the past 50 years. Loss of pine forests from pine-wilt disease is thought to be a major threat to this species. In contrast, V. ciliatum was found over a range of more than 300 km in western Japan. Habitats of both species were heavily fragmented. The genetic diversity and phylogenetic relationships of the three species were studied using nine simple-sequence repeat loci. V. sieboldii and V. ciliatum have a close genetic relationship, although their present growth ranges are widely separated. Despite its limited growth range and the limited number of remaining plants, the genetic diversity of V. sieboldii is similar to that of another endangered species, V. ciliatum, and that of the widely grown species, V. oldhami. Seven populations of the former two species were used to create population-based dendrograms. They were separated into three groups: three populations of V. sieboldii, two mountainous populations of V. ciliatum, and two coastal populations of V. ciliatum. The separation was supported by high bootstrap values. Isolation factors of the two population groups in V. ciliatum are discussed.     

Impact of Red Deer Cervus elaphus Grazing on Bilberry Vaccinium myrtillus and Composition of Ground Beetle (Coleoptera, Carabidae) Assemblage

We studied the role of red deer Cervus elaphus L. as ecosystem modifier in boreal forest (Tingvoll municipality, 62°52′ N, 8°20′ E, Norway), during early summer of 2001. The effect of grazing by red deer on ground beetles (Carabidae) abundance and diversity was investigated across a gradient of grazing pressures. We trapped ground beetles by pit-fall traps from three homogeneous winter grazing areas (ungrazed, medium grazed, heavily grazed). Bilberry Vaccinium myrtillus (the main winter food for red deer) was sampled and its dry weight was measured for the three locations. Gradient analyses showed that grazing by red deer affects carabid species composition. Grazing significantly affected the amount of bilberry, which correlated with species variation. According to our predictions, we found a higher abundance of carabids in the heavily grazed location, but the species richness and the diversity indices were similar for the three areas. This study shows that overall species composition is altered along a gradient as consequence of red deer winter grazing and that red deer act as ecosystem engineer, by reducing the bilberry heather which dominates the field layer in early summer.     

Evolution of a hybrid zone of two willow species (Salix L.) in the European Alps analyzed by RAD-seq and morphometrics

Natural hybridization of plants can result in many outcomes with several evolutionary consequences, such as hybrid speciation and introgression. Natural hybrid zones can arise in mountain systems as a result of fluctuating climate during the exchange of glacial and interglacial periods, where species retract and expand their territories, resulting in secondary contacts. Willows are a large genus of woody plants with an immense capability of interspecific crossing. In this study, the sympatric area of two diploid sister species, S. foetida and S. waldsteiniana in the eastern European Alps, was investigated to study the genomic structure of populations within and outside their contact zone and to analyze congruence of morphological phenotypes with genetic data. Eleven populations of the two species were sampled across the Alps and examined using phylogenetic network and population genetic structure analyses of RAD Seq data and morphometric analyses of leaves. The results showed that a homoploid hybrid zone between the two species was established within their sympatric area. Patterns of genetic admixture in homoploid hybrids indicated introgression with asymmetric backcrossing to not only one of the parental species but also one hybrid population forming a separate lineage. The lack of F1 hybrids indicated a long-term persistence of the hybrid populations. Insignificant isolation by distance suggests that gene flow can act over large geographical scales. Morphometric characteristics of hybrids supported the molecular data and clearly separated populations of the parental species, but showed intermediacy in the hybrid zone populations with a bias toward S. waldsteiniana. The homoploid hybrid zone might have been established via secondary contact hybridization, and its establishment was fostered by the low genetic divergence of parental species and a lack of strong intrinsic crossing barriers. Incomplete ecological separation and the ability of long-distance dispersal of willows could have contributed to the spatial expansion of the hybrid zone.     

Vectorial capacity of Triatoma guasayana (Wygodzinsky & Abalos) (Hemiptera: Reduviidae) compared with two other species of epidemic importance

Triatoma guasayana (Wygodzinsky & Abalos) is a peridomestic triatomine with epidemiological importance in Bolivia, that may play an important role in the transmission of Trypanosoma cruzi (Chagas). In this study, two parameters of vectorial capacity were evaluated: the interval of feeding-defecation time and metacyclogenesis, in adult males and females and nymphal instars II to V of T. guasayana with comparisons with Triatoma infestans (Klug) and T. sordida (Stal). The results showed a close relationship between ingestion of blood and beginning of defecation. Values were negative in T. infestans, and T. sordida for instars II, III, IV, and V and also males and females but were positive in female T. sordida. Triatoma guasayana showed only negative values for instar II. Adults and nymphs began defecation as soon as they had finished feeding and required an average of 29.8 min. The analysis of metacyclogenesis showed that T. guasayana was superior to T. infestans and T. sordida. However, the vectorial effectiveness of T. guasayana was significantly affected regarding the percentage of metacyclic trypomastigotes during instars III to V and showed a progressive increase. Females had higher proportions despite their ingestion being half that of T. infestans. The different instars of T. guasayana had a higher parasitic load than those of T. sordida and, although ingestion was 1/3 of that of female T. infestans, there was a progressive increase in metacyclic trypomastigotes in the different nymphal stages of T. guasayana that decreased in adults.     

Ultraviolet reflection of berries attracts foraging birds. A laboratory study with redwings (Turdus iliacus) and bilberries (Vaccinium myrtillus)

Unlike humans, birds perceive ultraviolet (UV) light (320 to 400 nm), a waveband which is known to play a role in avian mate choice. However, less attention has been paid to the role of UV light in avian foraging. Some blue, violet and black berries reflect UV light. The colour of berries might be an effective advertisement for avian seed dispersers and indicate the stage of fruit ripeness. We conducted an experiment to test how the UV reflection of berries affects birds'' foraging. Redwings were allowed to choose between UV-reflecting bilberries and rubbed bilberries (UV reduced) in the presence and absence of UV light. We used wild-caught adult and hand-raised juvenile birds to assess possible differences between experienced and naive birds. We found that adult redwings preferred UV-reflecting berries when UV illumination was present, but when UV illumination was absent, they did not distinguish between the two berry types. Our study therefore shows, for the first time, that UV wavelengths are used when birds feed on fruit. However, naive birds showed no preferences, suggesting that age and/or learning may affect frugivore preference for UV reflectance.     

Seed dormancy and germination behaviour in two Euphrasia species (Orobanchaceae) occurring in the Swiss Alps

The optimal time for germination of a seed depends on environmental conditions of its habitat, the life cycle of the germinating plant, and the conditions for successful establishment, growing and reproduction. We studied the germination behaviour of the alpine annual Euphrasia minima and an alpine ecotype of E. salisburgensis in a lowland garden experiment. Seeds of both species and their hybrids germinated at constant (5 °C) and at varying temperatures (3–10 °C), and never before spring after seed ripening. Germination was spread over 3 years, which suggests that the seeds formed a persistent seed bank. The two species together with E. minima and E. minima hybrids differed significantly in the germination rate in the first and second spring.  © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society , 2008, 156 , 649–656.     

Ontogenetic shifts in interactions of two dominant shrub species in a semi‐arid coastal sand dune system

Question: How does the interaction between two dominant shrub species in a coastal sand dune community change during their life history? Does this interaction influence their population dynamics? Location: A semiarid coastal sand dune system in southeast Spain. Methods: For 3 years we monitored physiological status, growth and reproductive effort of Juniperus phoenicea and Pistacia lentiscus, the dominant shrub species, growing either alone or in close spatial association. We also recorded adult mortality patterns and characterized seedling survival, soil properties and microclimate conditions beneath canopies and in bare ground. Results and conclusions: There was a strong bi‐directional interaction between the two studied species, with a net balance that changed in sign with increasing plant development. While mature individuals facilitated the establishment of seedlings of both species, adult mortality patterns suggested asymmetric competition at later life stages. The interaction with Pistacia negatively affected growth of juniper and contributed to its high mortality rates, while juniper had almost no effect on mature Pistacia individuals. Physiological data suggested that Pistacia had a competitive advantage over juniper, most likely because of differences in rooting patterns and tolerance to salinity, which may determine the source of water available for each species. Community dynamics are governed by facilitation at the seedling stage and shaped by differences in physiological traits in adult plants. Plant‐plant interactions, which are strongly affected by environmental gradients, are important drivers of community dynamics in this system.