Genotypical and multiple phenotypical traits discriminate Salix × rubens Schrank clearly from its parent species

Most studies on Salix hybrids concerning the diversity in a hybrid complex included typical morphological characteristics of leaves, buds, twigs and flowers for comparison with genotypic traits. Our analyses are based on a set of phenotypical traits of 19 clones of the S. alba/S. fragilis-aggregate which includes characteristics as phenology, growth, and composition of secondary leaf compounds, for the first time additional to morphological traits. Three clearly distinct groups (S. alba L., S. fragilis L., and S. × rubens Schrank) could be identified based on phenotypical traits and ITS1 and 5.8S nrDNA sequences. S. × rubens revealed additivities at variable ITS1 and 5.8S positions as well as intermediate morphology and secondary compound pattern, but was characterised by significant earlier foliation start. This property leads to a better utilization of the vegetation period and may explain the detected better growth compared to the parent species and therefore also may have contributed to the widespread occurrence of S. × rubens in Central Europe.     

Nuclear cyp73 intron fragment length polymorphism supports morphological analysis of Salix species and hybrids

Abstract

The polyploid Salix alba L.–Salix fragilis L. hybrid complex still presents major difficulties in morphological identification. Most of the measured characters show a low diagnostic value for unambiguously identifying the parental species and their hybrid Salix × rubens Schrank due to continuous variation creating a large overlap in leaf and catkin morphology. Fragment length polymorphism of nuclear cyp73 intron markers was used to identify species and hybrids. This multilocus genotyping could be applied in a morphological analysis of trees from hybrid zones and allowed to demonstrate that morphological features of leaves and catkins clearly separated S. alba from S. fragilis. The hybrid individuals largely overlapped with both parental species but appeared to be morphologically more similar to S. fragilis than to S. alba. Cyp73 analysis of 11 Salix taxa revealed intermediate positions of two hybrid taxa with S. alba, namely S. × rubens and S. × sepulcralis Simonkai with their respective parental species S. fragilis and S. babylonica L. Additionally, the cyp73 intron multilocus genotypes clustered tetraploid taxa separately from diploid willows. Cyp73 introns are valuable markers for fast, reliable and straightforward genotyping in willow species and hybrids.     

The ribosomal ITS region as a marker to detect hybridization in pines

Amplified fragment length polymorphism (AFLP) analysis of 26 trees of three Salix taxa: Salix alba L. (White Willow), S. fragilis L. (Crack Willow) and their hybrid S. x rubens Schrank, across an example of their habitat range in south-west Germany, supported the distribution previously determined using morphological characterization. UPGMA and principal coordinates analysis of the AFLP data revealed three distinct clusters corresponding to the three taxa. In addition, AFLP analysis on individuals which were difficult to identify morphologically revealed that they were either the hybrid S. x rubens or S. fragilis. Four specimens of S. fragilis were indistinguishable with three primer combinations suggesting they are members of one clone.     

Preference–performance relationship in the gall midge Rabdophaga rosaria: insights from a common‐garden experiment with nine willow clones

1. Oviposition preferences of herbivorous insects are predicted to match offspring performance on different host taxa or on conspecific host genotypes. In gall‐inducing insects, host‐plant properties such as growth rate and gall size, which are determined by plant genotype and growing conditions, may have a significant impact on offspring performance and, hence, should influence oviposition site selection. 2. The present study investigated host preference of the European rosette willow gall midge Rabdophaga rosaria (Loew) in relation to offspring success on seven clones of Salix myrsinifolia Salisb. and two naturally hybridised S. myrsinifolia × phylicifolia L. clones growing in a replicated design in an experimental field under two fertilisation regimes. For each clone, the average growth rate, number of shoot tips, and leaf and gall size were determined, and their effects on midge preference and larval survival were examined. 3. Main shoot height, number of shoot tips, and gall size were significantly affected by clone. The midges clearly preferred certain clones over the others, but preferences were not related to willow growth traits or to gall size. Survival probability was higher in large than in small galls, but females did not prefer large‐leaved clones that produced the biggest rosette galls. Midge oviposition was also uncorrelated with prior rates of leaf‐rust infection and with feeding preferences of voles and folivorous insects. 4. The weak preference–performance relationship of R. rosaria within S. myrsinifolia is probably explained by evolutionary constraints that prevent generalist insects from achieving an ability to discriminate among conspecific hosts of variable quality.     

Greater impact of host plant species on oviposition of a willow leaf beetle <Emphasis Type="Italic">Plagiodera versicolora</Emphasis> Laicharting (Coleoptera: Chrysomelidae) during the adult stage than in developing larval stage

In some herbivorous insects, such as Coleoptera and aphids, not only the host species of larvae, but also those of adults should be considered as key determinants of potential fecundity because oviposition is affected by the quality of host species during both larval and adult stages. This study examined the relatively greater impact on host species of the larval or adult stage on oviposition of the willow leaf beetle Plagiodera versicolora Laicharting (Coleoptera: Chrysomelidae). We conducted an experiment using a 2 × 2 experimental design, in which either of two different host plant species was fed in larval and adult stages. Females fed on a locally unavailable host Salix eriocarpa in the adult stage did not lay any eggs, but those fed on the locally available host S. babylonica laid 67–75 eggs on average, irrespective of larval host species. Such reproductively inactive females fed S. eriocarpa as an adult host recovered reproductive activity within 3 weeks after changing the host species to S. babylonica. This result indicated that the host species fed in the adult stage had a greater impact on oviposition than in the larval stage.     

Oviposition site preference and developmental performance of a gall‐inducing leafhopper on galled and non‐galled host plants

Oviposition preferences of herbivorous insects affect offspring performance. Both positive and negative links between oviposition preference and offspring performance have been reported for many species. A gall‐inducing leafhopper, Cicadulina bipunctata Melichar (Hemiptera: Cicadellidae), feeds on various Poaceae plants and induces galls of enhanced nutritional value for their offspring. Although gall induction by C. bipunctata improves nymphal performance, the oviposition preference of females between galled and non‐galled host plants is still unclear. In this paper, the nymphal performance and oviposition and feeding‐site preference of C. bipunctata were investigated using galled wheat, Triticum aestivum L., and non‐galled barley, Hordeum vulgare L., as host plants. The survival rate of C. bipunctata on wheat was significantly higher than on barley. In the choice test, significantly more eggs were laid into barley, whereas the number of eggs deposited on both hosts was not significantly different in the no‐choice test. The number of settling individuals per leaf area was not significantly different between wheat and barley, suggesting no clear preference for oviposition between these plants. Experience as a nymph with a growing host did not affect oviposition preference as adult female. The inconsistent correspondence between offspring performance and oviposition preference of C. bipunctata may reflect the high mobility of nymphs and/or differences in leaf area between host plants. The results indicate that the previous finding that oviposition preference and offspring performance are not always positively correlated in herbivorous insects is applicable to gall‐inducing insects.     

The chemical composition of plant galls: are levels of nutrients and secondary compounds controlled by the gall-former?

The chemical composition of galled and ungalled plant tissue was compared in a series of experiments. Gall and adjacent plant tissue was analysed for 20 species of gall-former on 11 different plant species. There were clear differences between galled and ungalled tissue in levels of nutrients and secondary compounds. Gall tissue generally contained lower levels of nitrogen and higher levels of phenolic compounds than ungalled plant tissue. The gall tissue produced by the same plant in response to different species of gall-former differed in chemical composition, as did the gall-tissue from young and mature galls of the same species. The chemical differences between gall and plant tissues were studied in more detail in two field manipulations. Firstly, the seasonal changes in phenolic biosynthesis in Pontania proxima and P. pedunculi (Hymenoptera: Tenthredinidae) gall tissue were compared to those of their host plants, Salix alba and S. caprea. In both types of gall tissue, phenolic levels declined as the season progressed, but levels in the surrounding plant tissue increased. When the gall insects were killed with insecticide, phenolic levels in the galled tissue dropped to the same level as those in adjacent plant tissue. Secondly, the density of Cynips divisa (Hymenoptera: Cynipidae) galls on Quercus robur leaves was reduced by removing half the galls present, either those from the central region of the leaf or those from the edge. Decreasing gall density increased the size of the remaining galls and the weight of the insects, but these effects were most marked when the galls remaining were growing centrally on the leaf, i.e. when the galls from the edge had been removed. Decreasing gall density increased the nitrogen content of the remaining galls, again to a greater extent in galls growing centrally on the leaf. The results of these studies suggest that the levels of nutrients and secondary compounds in gall tissue are usually markedly different to those of surrounding plant tissue, and that gall-formers may produce species-specific and temporally variable changes in the chemical composition of gall tissue. Received: 7 July 1997 / Accepted: 29 September 1997     

Oviposition and larval performance of Rabdophaga terminalis on Salix spp. with special consideration to bud size of host plants

Females of the gall midge Rabdophaga terminalis (H. Loew) (Diptera: Cecidomyiidae) are very selective in their choice of host plants at oviposition. In preference trials, eggs were laid almost exclusively on S. alba and S. fragilis. One single oviposition occurred on S. viminalis but none on S. triandra, S. daphnoides or S. smithiana. Significantly more eggs were laid on S. alba than on S. fragilis. No differences were detected between clones of the same species regarding oviposition in laboratory trials. Within the species of S. alba, larger buds were preferred. However, this did not explain the preference of S. alba to S. fragilis. There was agreement between plant species selected by the females and survival of the larvae. No galls developed when eggs were transferred to species that were not oviposited on. There was no difference between S. alba and S. fragilis in larval growth, but after two weeks of development there was a significantly higher proportion of larvae in cocoons and pupae on S. alba. There was a negative linear relationship between weight of larvae and larval number per gall, indicating larval competition. The negative slope was steeper for S. alba than for S. fragilis when larvae were weighed after two weeks of development. There were some discrepancies between laboratory and field data on infestation of S. alba and S. fragilis. Higher infestation levels were related to denser stands in the field.

---

Résumé Etude de la ponte et des performances larvaires de Rabdophaga terminalis (Diptera; Cecidomyiidae) sur plusieurs espèces de saules avec examen particulier de l'influence de la taille des bourgeons.La ponte et les performances larvaires de la cécidomyie galliforme, Rabdophaga terminalis (H. Loew) ont été étudiées sur plusieurs espèces et clones de saules cultivés en Suède. Les femelles sélectionnent avec soin les plantes hôtes lors de la ponte. Dans des essais préférentiels, les oeufs ont été pondus presque exclusivement sur S. alba et S. fragilis; une ponte a été observée sur S. viminalis et aucune sur S. triandra, S. daphnoïdes ou S. smithiana. Significativement plus d'oeufs ont été pondus sur S. alba que sur S. fragilis. Les essais au laboratoire n'ont pas permis de déceler des différences entre clones de la même espèce. Chez S. alba, les plus gros bourgeons étaient préférés, mais ceci ne permet pas d'expliquer la préférence pour S. alba par rapport à S. fragilis. Il y a coïncidence entre les plantes choisies par les femelles et al survie des larves; il n'y avait pas développement de galles quand des oeufs étaient transférés sur des espèces qui n'avaient pas reçu de pontes. La croissance larvaire sur S. alba et S. fragilis ne présentait pas de différences, mais après 2 semaines de développement il y avait significativement plus de larves en cocons et pupes sur S. alba. La corrélation entre le poids des larves et le nombre de larves par cellule était linéaire et négative, ce qui indique une compétition larvaire; la pente était plus raide pour S. alba que pour S. fragilis quand les larves étaient pesées au bout de 2 semaines de développement. Il y a eu quelques discordances entre les résultats au laboratoire et les données de terrain sur la contamination de S. alba et S. fragilis. Les plus fortes contaminations étaient observées à l'extérieur sur pépinières denses.

     

Variation in the uptake of Arsenic, Cadmium, Lead, and Zinc by different species of willows Salix spp. grown in contaminated soils

The experiment assessed the variability of in seven clones of willow plants of high biomass production (Salix smithiana S-218, Salix smithiana S-150, Salix viminalis S-519, Salix alba S-464, Salix ’Pyramidalis’ S-141, Salix dasyclados S-406, Salix rubens S-391). They were planted in a pots for three vegetation periods in three soils differing in the total content of risk elements. Comparing the calculated relative decrease of total metal contents in soils, the phytoextraction potential of willows was obtained for cadmium (Cd) and zinc (Zn), moderately contaminated Cambisol and uncontaminated Chernozem, where aboveground biomass removed about 30% Cd and 5% Zn of the total element content, respectively. The clones showed variability in removing Cd and Zn, depending on soil type and contamination level: S. smithiana (S-150) and S. rubens (S-391) demonstrated the highest phytoextraction effect for Cd and Zn. For lead (Pb) and arsenic (As), the ability to accumulate the aboveground biomass of willows was found to be negligible in both soils. The results confirmed that willow plants show promising results for several elements, mainly for mobile ones like cadmium and zinc in moderate levels of contamination. The differences in accumulation among the clones seemed to be affected more by the properties of clones, not by the soil element concentrations or soil properties. However, confirmation and verification of the results in field conditions as well as more detailed investigation of the mechanisms of cadmium uptake in rhizosphere of willow plants will be determined by further research.     

Influence of phenolglucosides and trichome density on the distribution of insects herbivores on willows

The effects of both trichome density and phenolglucoside content of leaves of 76 willow hybrids (Salix alba x fragilis) were measured to estimate their influence on the distribution of Phratora vitellinae (L.), Plagiodera versicolora Baly (Coleoptera: Chrysomelidae) and Pontania proxima (Lepeletier 1823) (Hymenoptera: Tenthredinidae) in a nursery at Gramont, Belgium.The willows showed differences in their phenolglucoside content and pilosity of leaves and are classified on these basis into four groups by a clustering method. Correlations and multiple regressions showed that these chemical and physical characteristics are good predictors of the abundance of insects. First, the abundance of larvae of Ph. vitellinae, adults of Pl. versicolora and galls of P. proxima is correlated positively with a high phenolglucoside content and a low pilosity of the leaves. Secondly, the distribution of adults of Ph. vitellinae and of larvae of Pl. versicolora is influenced by neither the chemical nor the physical leaves characteristics studied.     

Molecular identification and characterization of Elsinoë murrayae (Synonym: Sphaceloma murrayae) from weeping willow

Sphaceloma murrayae is a significant fungal pathogen of Salix spp. It causes greyish‐white leaf spots, which were reported worldwide except in China. Its morphological characteristics were described in the early literature; however, there is a lack of molecular information pertaining to this fungus. This study identified and characterized three fungal isolates that obtained from weeping willow leaf spots in China. Based on disease symptoms, morphological characteristics and single nomenclature rules for fungi, these isolates are proposed to be new combinations of Elsinoë murrayae (Synonym: S. murrayae). Phylogenetic analysis that combined internal transcribed spacer (ITS), large subunit (LSU), RBP2 and TEF1‐α DNA sequences indicated that E. murrayae isolates and Elsinoë salicina—another Elsinoë sp. isolated from Salix sp.—were distinguishable species. With trypan blue staining and stereomicroscopic observation, we found that large‐scale cell death occurred at 2 days postinoculation (dpi) and slight disease symptoms started at 3 dpi when the conidia were inoculated on Salix babylonica leaves. Pathogenicity analysis revealed that three isolates can successfully infect mature leaves of S. babylonica, Salix fragilis and Salix suchowensis, but not Salix matsudana. In addition, a necrosis‐ and ethylene‐inducing‐like proteins’ (NLP) gene, named EmNLP1, was cloned. The cytotoxicity of EmNLP1 was confirmed by transient assay in tobacco. During infection, EmNLP1 dramatically peaked at 2 dpi and maintained a high‐level expression in the necrosis lesion growing stage.     

Phytoextraction of Cd and Zn from agricultural soils by Salix ssp. and intercropping of Salix caprea and Arabidopsis halleri

Contamination of agricultural topsoils with Cd above guideline values is of concern in many countries throughout the world. Extraction of metals from contaminated soils using high-biomass, metal-accumulating Salix sp. has been proposed as a low-cost, gentle remediation strategy, but reasonable phytoextraction rates remain to be demonstrated. In an outdoor pot experiment we assessed the phytoextraction potential for Cd and Zn of four willow species (Salix caprea, S. fragilis, S. × smithiana, S. × dasyclados) and intercropping of S. caprea with the hyperaccumulator Arabidopsis halleri on three moderately contaminated, agricultural soils. Large concentrations of Cd (250 mg kg⁻¹) and Zn (3,300 mg kg⁻¹) were determined in leaves of Salix × smithiana grown on a soil containing 13.4 mg kg⁻¹ Cd and 955 mg kg⁻¹ Zn, resulting in bioaccumulation factors of 27 (Cd) and 3 (Zn). Total removal of up to 20% Cd and 5% Zn after three vegetation periods were shown for Salix × smithiana closely followed by S. caprea, S. fragilis and S. × dasyclados. While total Cd concentrations in soils were reduced by up to 20%, 1 M NH₄NO₃-extractable metal concentrations did not significantly decrease within 3 years. Intercropping of S. caprea and A. halleri partly increased total removal of Zn, but did not enhance total Cd extraction compared to single plantings of S. caprea after two vegetation periods.     

Behavioural,ecological and genetic evidence confirm the occurrence of host‐associated differentiation in goldenrod gall‐midges

Host‐associated differentiation (HAD) is considered a step towards ecological speciation and an important mechanism promoting diversification in phytophagous insects. Although the number of documented cases of HAD is increasing, these still represent only a small fraction of species and feeding guilds among phytophagous insects, and most reports are based on a single type of evidence. Here we employ a comprehensive approach to present behavioural, morphological, ecological and genetic evidence for the occurrence of HAD in the gall midge Dasineura folliculi (Diptera: Cecidomyiidae) on two sympatric species of goldenrods (Solidago rugosa and S. gigantea). Controlled experiments revealed assortative mating and strong oviposition fidelity for the natal‐host species. Analysis of mitochondrial DNA showed an amount of genetic divergence between the two host‐associated populations compatible with cryptic species rather than host races. Lower levels of within‐host genetic divergence, gall development and natural‐enemy attack in the S. gigantea population suggest this is the derived host.     

The heterosis estimates for growth and survival traits in sterlet and Siberian sturgeon purebreds and hybrids

The aim of the present study was to estimate and compare the growth and survival traits of the hybrids and purebreds produced by crossing the Siberian sturgeon (Acipenser baerii) (S) and sterlet (Acipenser ruthenus) (St) in order to determine the heterosis effect in the F1 generation. We compared the breeding conditions, mean body weight (BW) and cumulative survival in the artificially produced hybrid crosses of sterlet and Siberian sturgeon with respect to their pure parental species in indoor and outdoor aquaculture systems at different developmental stages. Fertilization and hatching rates were found to be significantly higher in S × S purebred compared to St × S hybrid. The highest values of BW were recorded in St × S hybrid (557.54 ± 179.7 g) on 862 days post-hatch (dph) while the highest cumulative survival was recorded in S × S purebred (14.3%). The recorded cumulative survival and mean BW was significantly lower in St × St purebred. The highest positive heterosis was recorded for mean BW of St × S hybrid (51.3% on 862 dph) throughout the sampling points. The studied sturgeon hybrids had higher mean BW compared to St × St purebred under suboptimal rearing conditions. Although there was no clear demonstration of the superiority in performance of reciprocal hybrids over purebreds, the St × S hybrid can be used for achieving better productivity in aquaculture systems.     

The effects of Laccaria proxima and fibrous pulp waste on the growth of nine container-grown conifer seedling species

 Japanese larch (Larix kaempferi), white spruce (Picea glauca), black spruce (Picea mariana), red spruce (Picea rubens), jack pine (Pinus banksiana), mugo pine (Pinus mugo), red pine (Pinus resinosa), Japanese black pine (Pinus thunbergii) and Douglas-fir (Pseudotsuga menziesii var. menziesii), were inoculated to test the effective host range of the ectomycorrhizal fungus Laccaria proxima and the possibility of utilizing pulp waste as a potting medium for containerized seedling production. Laccaria proxima tended to improve the container growth of Japanese black pine and white spruce, and significantly improved that of jack pine, mugo pine, black spruce, red spruce and Douglasfir. The growth of red pine and Japanese larch were only slightly improved with L. proxima. Pulp waste (33% by volume) had negative effects on tree seedling growth, except for Douglasfir (no significant effect). The interactions of Laccaria proxima and pulp waste varied; the hosts were significantly positive (P<0.01) in the case of jack pine and black spruce, but there was no significant effect for the rest. Negative effects were found with Japanese black pine. Use of pulp waste in seedling production of jack pine, black spruce, mugo pine, red spruce and Douglasfir inoculated with L. proxima and of Japanese black pine both with and without L. proxima is feasible, but further research is necessary to determine the optimal percentage of pulp waste that can be utilized in seedling production of tree species and the field performance of these seedlings. Accepted: 30 August 1995     

Wide spread invasion without sexual reproduction? A case study on European willows in Patagonia,Argentina

Willows of the Salix alba–Salix fragilis complex, native to western Eurasia, represent typical invaders of floodplain ecosystems worldwide. Introduced to South America by European settlers probably at the end of the nineteenth century, their distribution has increased significantly along the rivers in Northern Patagonia. This case study carried out mainly in the area around Lake Nahuel Huapi aims to analyze clonal structures and their spatial distribution using molecular markers as well as to relate the observed patterns to settlement history and life history traits of this species complex. Leaf material from 171 trees was collected along selected river floodplains in Northern Patagonia and genotypes were determined at six microsatellite loci. Including 62 reference samples of the S. alba–S. fragilis complex from German rivers, Probability of Identity (P _ID) was calculated and a Principal Coordinate Analysis (PCoA) conducted. From the altogether thirteen different genotypes detected, one dominant genotype (female) formed monoclonal stands along most of the studied river stretches. The maximum linear distance between the most remote ramets of this clone was 790 km. Evidence arose that the colonizing process so far is exclusively based on vegetative propagation in the focal study area and is obviously attributable to the pronounced brittleness of the hybrid parent S. fragilis. However, outside this area the occurrence of male trees and a diversity of genotypes indicate that evolutionary processes by recombination are involved within the willow complex. Therefore, an increase in genotypes can be assumed when male individuals and therefore sexual reproduction would appear in the area around Lake Nuhuel Huapi. This could be a crucial point for the long-term invasion success of the taxa when climatic and other environmental conditions will change in Southern Argentina.     

Combined effects of zinc and algal food on the competition between planktonic rotifers, <Emphasis Type="Italic">Anuraeopsis fissa</Emphasis> and <Emphasis Type="Italic">Brachionus rubens</Emphasis> (Rotifera)

We evaluated the combined effects of algal (Chlorella vulgaris) food levels (low, 0.5 × 10⁶ (or 2.9 μg C ml⁻¹); and high, 1 × 10⁶ cells ml⁻¹ (or 5.8 μg C ml⁻¹)) and zinc concentrations (0, 0.125, and 0.250 mg l⁻¹ of ZnCl₂) on the competition between two common planktonic rotifers Anuraeopsis fissa and Brachionus rubens using their population growth. Median lethal concentration data (LC₅₀) (mean ± 95% confidence intervals) showed that B. rubens was more resistant to zinc (0.554 ± 0.08 mg l⁻¹) than A. fissa (0.315 ± 0.07 mg l⁻¹). A. fissa when grown alone or with Zn was always numerically more abundant than B. rubens. When grown in the absence of zinc, under low- and high-food levels, the peak abundances of A. fissa varied from 251 ± 24 to 661 ± 77 ind. ml⁻¹, respectively, and the corresponding maxima for B. rubens were 52 ± 3 and 102 ± 18 ind. ml⁻¹. At a given food level, competition for food reduced the peak abundances of both rotifers considerably. Increase in Zn concentration also lowered the rotifer abundances. The impact of zinc on competition between the two-rotifer species was evident at low-food level, mainly for A. fissa. At zinc concentrations of 0 and 0.125 mg l⁻¹, the populations of both rotifers continued to grow for about 10 days, but thereafter B. rubens began to decline. Role of zinc on the competitive outcome of the two species is discussed in relation to the changing algal densities in natural water bodies.     

Symbiont physiology and population dynamics before and during symbiont shifts in a flexible algal‐cnidarian symbiosis

For cnidarians that can undergo shifts in algal symbiont relative abundance, the underlying algal physiological changes that accompany these shifts are not well known. The sea anemone Anthopleura elegantissima associates with the dinoflagellate Symbiodinium muscatinei and the chlorophyte Elliptochloris marina, symbionts with very different tolerances to light and temperature. We compared the performance of these symbionts in anemones maintained in an 8–11.5 month outdoor common garden experiment with simulated intertidal conditions and three levels of shading (2, 43, and 85% ambient irradiance). Symbiont densities, mitotic indices, photophysiology and pigments were assessed at three time points during the summer, a period of high irradiance and solar heating during aerial exposure. Whereas S. muscatinei was either neutrally or positively affected by higher irradiance treatments, E. marina responded mostly negatively to high irradiance. E. marina in the 85% irradiance treatment exhibited significantly reduced P_max and chlorophyll early in the summer, but it was not until nearly 3 months later that a shift in symbiont relative abundance toward S. muscatinei occurred, coincident with bleaching. Symbiont densities and proportions remained largely stable in all other treatments over time, and displacement of S. muscatinei by E. marina was not observed in the 2% irradiance treatment despite the potentially better performance of E. marina. While our results support the view that rapid changes in symbiont relative abundance are typically associated with symbiont physiological dysfunction and bleaching, they also show that significant temporal lags may occur between the onset of symbiont stress and shifts in symbiont relative abundances.     

A foliar morphometric approach to the study of salicaceae

An assemblage of leaves of four species of willows (Salix viminalis, S. alba, S. fragilis, andS. caprea), two of their hybrids (S. alba ×fragilis andS. caprea ×viminalis), two species of poplars (Populus alba andP. tremula), and two “external” species (Elaeagnus angustifolia andPyrus salicifolia) was analyzed. The study was designed to determine whether leaves that are very close in shape but belong to different species, particularly the elongated leaves ofS. viminalis, S. alba, S. fragilis, E. angustifolia, andP. salicifolia, could be discriminated by continuous foliar characters (that is, vegetative characters), despite both the great foliar polymorphism met in Salicaceae (especially in the genusPopulus) and hybridization problems. Our results show that multivariate analyses (principal component analysis [PCA] and cluster analysis) of an appropriate character set enable leaves to be classified in their own species at more than 98 %, even in these difficult conditions. It can be seen from this work that PCA is a good tool when it keeps a maximum of total variability; that is, when there are few taxa; on the other hand, cluster analysis is more appropriate with many taxa. One can then envisage the application of this morphometric approach to fossil-imprint determination, in which even fragmentary paleobotanical remains could be included. This would give access to real biodiversity of tertiary flora and to intraspecific variability.

---

Résumé  Un assemblage de feuilles de quatre espèces de saules (Salix viminalis, S. alba, S. fragilis, etS. caprea), deux de leurs hybrides (S. alba ×fragilis etS. caprea ×viminalis), ainsi que deux espèces de peupliers (Populus alba etP. tremula), et deux espèces “externes” (Elaeagnus angustifolia etPyrus salicifolia) a été étudié. Le but était de savoir si des feuilles de forme très proche mais d’espèces différentes (en particulier les feuilles allongées deS. viminalis, S. alba, S. fragilis, E. angustifolia, etP. salicifolia) pouvaient être discriminées par des caractères foliaires (donc végétatifs) continus, et ce malgré le très grand polymorphisme foliaire existant chez les Salicacées (surtout chez le genrePopulus), et les problèmes d’hybridation. Il en a résulté que les analyses multivariées (ACP et analyse agrégative) associées à un jeu de caractères approprié, permettent à plus de 98% le classement des feuilles dans leur propre espèce, même dans ces conditions difficiles. Il ressort de ce travail que l’ACP n’est un bon outil que lorsqu’ elle conserve un maximum de la variabilité totale, c’est-à-dire ici, quand les taxa sont peu nombreux; en revanche, l’analyse agrégative exprime le maximum de ses capacités en présence d’un grand nombre de taxa. On peut alors envisager l’application de cette approche morphométrique à la détermination d’empreintes fossiles, dans le but d’inclure même les restes fragmentaires dans les études paléobotaniques, ce qui donnerait accès à la réelle biodiversité des flores tertiaires et à la variabilité existant au sein des espèces.

     

A report on <Emphasis Type="Italic">Penicillium</Emphasis> in the intramural and extramural air of residential areas of Nagpur city (India)

Prevalence of different species of Penicillium and their concentrations per cubic meter of air were evaluated with the use of Hi-Air sampler system Mark II (Hi-Media Laboratories Ltd., India) in the air of homes (bed-rooms) at four different sites in Nagpur. At each of these sites, air sampling was done fortnightly in triplicate for 2 years duration from June 2000 to May 2002. The sampling was also done in triplicate for the outdoor air in the vicinity of each home on the same day immediately after the indoor sampling was over. The mean concentration of Penicillium colony forming units at four different sites in the indoor air was 32, 46.9, 35 and 35.4 CFU/m³, respectively, whereas in the outdoor air at these same four sites, the mean concentration was 24, 28, 25 and 25.8 CFU/m³ respectively. The Penicillium concentration in the indoor air was found to be higher in winter than in other seasons (ANOVA, p < 0.05). Concentration of Penicillium spp. in intramural environment was always higher than that in extramural environment. Statistically significant difference existed between intramural and extramural environments at all the sites, with maximum difference at a site, which is old crowded area of the city. During the 2-years investigations, 11 species of Penicillium were isolated from the indoor air while nine species were isolated from the air outside the homes. The dominant species of Penicillium in indoor as well as outdoor air were P. citrinum (33.78 and 32.81), P. oxalicum (19.70 and 22.60), and P. chrysogenum (17.64 and 14.50). The percentage of the Penicillium in the indoor air was 10.70 while it was 8.36 in outdoor air. Indoor air showed the presence of P. glaber and P. sclerotiorum, which were absent in the outdoor air.