Geographical barriers and ecological gradients: Geographical distribution of the subspecies and morphotypes of Deutonura deficiens Deharveng, 1979 (Collembola: Neanuridae)

This work explores the links between ecogeographical barriers and clines, and the boundaries of infraspecific biological entities. The distribution of the three subspecies and eight morphotypes of the Neanurinae Deutonura deficiens (Collembola) are mapped and commented based on 570 records. The species inhabits a wide range of forest habitats from the north of Portugal to southeastern France. The subspecies and morphotypes constitute homogeneous geographic sets arranged as a mosaic of closely related forms. A few overlapping zones between subspecies or morphotypes have been detected, some of them having the character of hybrid zones; on the whole however, overlap is small or rare and allopatry or parapatry is the general pattern. Current range boundaries of subspecies and morphotypes were found to be usually not determined by major hydrographical and topographical barriers, with the noticeable exception of the Rhône River. At subspecies level, the morphological cline of increasing tuberculization correlated to the bioclimatic gradient from Mediterranean to Atlantic climates, already recorded by Deharveng (1984. Polymorphisme et polytypisme morphologiques chez quelques Neanurinae européens. Rev. Ecol. Biol. Sol. 21, 533–562), is confirmed on the present data set. Conversely, ecological boundaries, known to constrain species distribution in many living groups of the region, do not fit the contact zones between the different morphotypes of the three subspecies of D. deficiens. The eight recognized forms appear to be at different degrees of reproductive isolation, illustrating active speciation process possibly inherited from recent ecogeographical events. A more detailed sampling on contact zones and a robust phylogenetic hypothesis are needed at this stage for progressing in our understanding of this complex pattern.     

Ecology of soil springtails (Collembola, Insecta) from pine woods and Rhododendron shrublands in the Central and Eastern Pyrenees (North Spain)

The collembological composition of samples from the Central and Western Pyrenees (Northern Spain) was studied. Soils from two biotopes (pine forest and Rhododendron shrub) were studied in Nuria and Vallibierna, using different diversity indices and multivariate analyses. Ten species were found that were endemic to the Iberian Peninsula. Three of these are exclusive to the Pyrenees: Ceratophysella elegans, Hypogastrura dasiensis and Protachorutes pyrenaeus. The greatest diversity was observed in the soils of Rhododendron, above all at Nuria. Collembola were most poorly represented in the pine forest of Vallibierna, where the endemic Hypogastrura meridionalis was the dominant species. Multivariate analyses indicated that the latter species characterizes this pine forest and separates it from all other biotopes studied. The evenness (E) was most pronounced in Nuria, where Folsomia manolachei was the characteristic species.     

Fast and efficient discrimination of the Isotoma viridis group (Insecta: Collembola) by PCR-RFLP

Identification of collembolan species is generally based on specific morphological characters, such as chaetotaxy and pigmentation pattern. However, some specimens do not match to described characters because these refer to adult specimens, often of one specific sex, or the characters are highly variable in adults (e.g. pigmentation, setae or furcal teeth). Isozymes have frequently assisted species discrimination, and also these may vary with developmental stage or environmental conditions. For identification of single species of the Isotoma viridis group, we present both direct sequencing of the cytochrome oxidase subunit II (COII) gene and a simple DNA-based molecular method.

Five PCR primers amplifying the COII region (717 bp) of the mitochondrial DNA were used. The sequences clearly separated the species I. viridis, I. riparia and I. anglicana, irrespective of colour varieties within the first species. DNA amplification products of different species can also be distinguished by digestion with restriction endonucleases, followed by gel electrophoresis for separation of fragments. This restriction fragment length polymorphism (RFLP), obtained after digestion with the endonucleases TaqI, VspI, MvaI and Bsp143I, revealed specific fragments that separated the three species from each other. Since restriction enzymes are sensitive to single base mutations, we suggest to use a combination of enzymes with at least two species-specific restriction sites when using the RFLP technique. For the I. viridis complex, VspI and Bsp143I appear to be an appropriate combination.     

Microbial biomass and activity in pine litter in the presence of Tomocerus minor (Insecta,Collembola)

Summary Laboratory microcosms were used to study microbial populations and biomasses developing in fragmented litter of Pinus nigra Arnold var. nigra (A. et G.). Direct observations (fungal standing crop and fluorescein-stainable mycelia), litter enzyme analyses (cellulase and dehydrogenase), and measurements by physiological methods (microbial CO₂ production and total microbial, fungal, and bacterial viable biomasses) were made at 3-week intervals for 15 weeks. Most variables showed great changes during this period, which were ascribed to a rise in litter moisture content during the initial phase of the experiment, and to substrate depletion towards its final phase. The addition of the collembolan Tomocerus minor (Lubbock) for 1 week enhanced cellulase activities by 4%. When the animals were introduced after 6 weeks, the fungal standing crop was enhanced, and the percentage of fluorescein-stainable mycelia was reduced. Dehydrogenase activity was increased by grazing when the microbial population had been established for 9 weeks or longer. Eucaryotic and procaryotic substrate-induced respiration were positively correlated, which was explained by partial segregation of resources for the two groups. Litter cellulase and dehydrogenase activity showed correlations by other techniques, indicating their suitability as parameters for microbial activity in general, and for the collembolan grazing impact on microbial activity in particular.     

Seasonal distribution of Xenylla brevispina (Collembola) in the canopy and soil habitat of a Cryptomeria japonica plantation

We investigated the life cycle and habitat use of an arboreal collembolan species, Xenylla brevispina, in the canopy and soil of a conifer (Cryptomeria japonica D. Don) plantation. The adaptive significance of migration between arboreal and soil habitats in the maintenance of its population in relation to the vertical structure of the forest is discussed. We sampled dead branches with foliage in the canopy (canopy litter) and on the forest-floor (soil litter). X. brevispina had one generation a year throughout the 3 years of the study. The mean densities of X. brevispina were similar in the canopy litter (0.06 to 14.57 g⁻¹ dry weight) and the soil litter (0.44 to 18.99 g⁻¹ dry weight). Seasonal patterns of density and relative abundance indicate that individuals of X. brevispina in the canopy were closely associated with those in the soil. These results suggest that vertical migration between the canopy and the soil might be a strategy allowing X. brevispina to be a predominant collembolan species in this forest.     

Different methods for the evaluation of species of the genus Mesaphorura (Collembola, Tullbergiinae)

Field studies and laboratory investigations based upon cultures, isoenzyme electrophoresis and RAPD-PCR were carried out to get a better understanding of the value of morphospecies within the genus Mesaphorura.Culturing of seven Mesaphorura species under constant as well as variable conditions provided a basis for evaluation of morphological characters, but did not yield any statistically supportable evidence that intraspecific variability reached interspecific delimitations.In enzyme tests, esterases gave the best results. The search for species-specific band patterns is, however, time and material consuming. DNA investigations using RAPD-PCR resulted in band patterns that appeared to be species specific. Nevertheless, these require further investigations.None of the studies carried out gave any conclusive evidence for invalidation of the morphologically defined species of the genus Mesaphorura.     

Inter- and intraspecific feeding selectivity of Folsomia candida (Willem) (Collembola,Isotomidae) on fungi

Summary Selective grazing of fungi by soil microarthropods may affect decomposition rates of litter materials and the structure of microarthropod and fungal communities. We developed laboratory methods to assay feeding selectivity and investigated the preferences of the collembolan Folsomia candida on three fungi: Acremonium sp., Paecilomyces varioti, and Penicillium citrinum. F. candida showed stronger preference for Acremonium sp. than for P. varioti and P. citrinum. Oviposition site selection followed the same pattern. Actively metabolizing hyphae of Acremonium sp. and P. varioti were preferred over senescent hyphae, while spores of P. citrinum were preferred over active hyphae. If microarthropod preference for active hyphae is extensive, microarthropod regulation of decomposition could be more important than their biomass indicates. Furthermore, as the P. citrinum results indicate, mechanisms of microbial dissemination may include selective grazing.Contribution in part to International Symposium on Faunal Influences on Soil Structure, Edmonton, Alberta, Canada (11–13 June 1984), organized by W. B. McGill; and the annual meeting of the Ecological Society of America, Minneapolis, Minnesota (17–21 June 1985)     

UV-B辐射和稻瘟病菌胁迫对水稻幼苗苯丙氨酸解氨酶活性和类黄酮含量的影响

本文通过盆栽试验研究增强UV-B辐射和稻瘟病菌联合作用对水稻幼苗叶片苯丙氨酸解氨酶活性(PAL)和类黄酮含量的影响。试验采用3个UV-B辐射强度(2.5 kJ·m^-2、5.0 kJ·m^-2和7.5 kJ·m^-2)、2个稻瘟病菌生理小种(Y98-16T和Y99-63C)对水稻(品种为“黄壳糯”和“合系41”)幼苗叶片进行处理, 测定水稻幼苗苯丙氨酸解氨酶活性和类黄酮含量的变化。结果表明: “黄壳糯”幼苗叶片苯丙氨酸解氨酶活性和类黄酮含量在2.5 kJ·m^-2和5.0 kJ·m^-2 UV-B辐射条件下显著增加, 而在7.5 kJ·m^-2 UV-B辐射条件下显著降低; 2.5~7.5 kJ·m^-2 UV-B辐射导致“合系41”的类黄酮含量显著增加, 5.0 kJ·m^-2 UV-B辐射导致“合系41”的苯丙氨酸解氨酶活性显著增加, 其他UV-B辐射条件下“合系41”的苯丙氨酸解氨酶活性增加不显著。接种稻瘟病菌Y98-16T导致“合系41”的苯丙氨酸解氨酶活性和类黄酮含量显著增加, “黄壳糯”的苯丙氨酸解氨酶活性降低, 类黄酮含量增加; 而接种稻瘟病菌Y99-63C显著降低了“黄壳糯”和“合系41”的苯丙氨酸解氨酶活性和类黄酮含量。UV-B辐射和稻瘟病菌联合作用导致“黄壳糯”苯丙氨酸解氨酶活性和类黄酮含量总体表现出降低的趋势, 而“合系41” 苯丙氨酸解氨酶活性和类黄酮含量一定程度上具有稳定或上升的趋势。总的来讲, UV-B辐射和稻瘟病菌联合作用导致“黄壳糯”敏感性增加, 而“合系41”抗性增强。     

Symbiosis with bacteria enhances the use of chitin by the springtail,Folsomia candida (Collembola)

Summary The relationship between Folsomia candida and chitin-degrading microorganisms was studied. On chitin agar, 10¹⁰ bacteria were isolated per g faeces, and 3.8×10¹¹ bacteria per g gut contents, 1/3 of them showing a clear (chitin-free) zone around the colony. The most abundant chitin-degrading bacteria were Xanthomonas maltophilia and Curtobacterium sp. To determine the bacterial contribution in the use of chitin by F. candida, a feeding experiment was carried out. F. candida were fed with chitin, either amended with or without tetracycline as an inhibitor of bacteria. When tetracycline was omitted the biomass of F. candida was increased compared to those fed chitin with tetracycline. However, this result was observed only when the food replacement intervals were long enough to allow bacterial colonization before ingestion of the food. In a food-selection experiment, a preference for chitin colonized with microorganisms as opposed to sterile chitin was found. The results indicate that a mutualistic symbiosis of F. candida with chitinolytic microorganisms is likely to enhance chitin degradation. This relationship is not only intra-intestinal but also involves an extra-intestinal phase.Dedicated to the late Prof. Dr. W. Kühnelt     

Mendeschilis a new genus of Microcoryphia (Insecta, Apterygota, Machilidae) from Spain

A new species and genus of Microcoryphia is described as a result of the detailed comparison of specimens from Italy and Spain which had been initially identified as Praemachilis excelsior. The new genus, named Mendeschilis has as its most important distinctive taxonomic characteristic the presence, in the male, of parameres in the VIII^th and IX^th urosternites, while Praemachilis (from Italy) has only one pair of parameres in the IX^th urosternite. Other anatomical characteristics which allow us to differentiate the new genus and the new species are described.     

Analysis of clonal germplasm from five Saccharum species: S. barberi , S. robustum, S. officinarum, S. sinense and S. spontaneum . A study of inter- and intra species relationships using microsatellite markers

In order to study relationships within and among species of the highly complex polyploid genus Saccharum, 30 clones from 5 species (S. barberi, S. officinarum, S. robustum, S. sinense, and S. spontaneum) and 6 cultivated clones were analyzed using 15 sugarcane simple sequence repeat (SSR) markers and two multivariate statistical methods. The origins of two species, S. barberi and S. sinense, are unclear, and it has been hypothesized that they arose from crosses of S. officinarum × S. spontaneum. S. robustum is suggested to be ancestral to S. officinarum, which, when crossed with S. spontaneum, principally comprise the genomes of commercial cultivars. Although our analyses supported S. robustum as being an ancestor of S. officinarum, and show the composition of commercial clones as expected, our results concerning the species S. barberi and S. sinense indicated them to be much less related to the main Saccharum germplasm pool than previous molecular marker investigations, suggesting that introgression from other genera may exist in their ancestry. The differing results of our analysis of S. barberi and S. sinense are likely attributable to more equal and larger numbers of clones studied in each species. Given the extremely high ploidy, the use of only 15 SSR markers enabled clear distinction of Saccharum species and clones, and also identified likely mislabeled accessions. In addition, the replication of DNA extraction, polymerase chain reactions, and fragment electrophoresis increased the robustness of our analysis.     

Population genetic structure of Orchesella cincta (Collembola; Hexapoda) in NW Europe, as revealed by microsatellite markers

We studied genetic variation and population differentiation in the springtail Orchesella cincta L. An earlier approach, using allozymes, revealed extremely low variation among and within populations from NW Europe. Microsatellite marker analysis showed higher genetic variation than allozymes, and agreed with the previously reported low population differentiation in the species. Analysis of molecular variance showed that genetic variation within populations amounted to 96.5% of the total variation, whereas the remaining 3.5% is accounted for by population differentiation. Population differentiation, as described by microsatellite markers and with the exception of one population, can be explained by an isolation by distance. Although the microsatellites are short, viz. only up to 12 repeat units, they appear to be useful tools in revealing population genetic structures in O. cincta.     

Molecular phylogeny of Chinese vegetable mustard (<Emphasis Type="Italic">Brassica juncea</Emphasis>) based on the internal transcribed spacers (ITS) of nuclear ribosomal DNA

Sequence variation of nuclear internal transcribed spacer regions of ribosomal DNA (ITS1, 5.8S rRNA and ITS2) from Chinese vegetable mustards (AB-genome) and its putative parents Brassica rapa (the A-genome) and Brassica nigra (the B-genome) were used to investigate the molecular phylogeny and the probable evolutional pattern of this amphidiploid species that uniquely formed in China. Totally, 16 accessions of Chinese vegetable mustard those covering nearly all the diverse variations were included in this study, and together with three accessions of B. rapa and one accession of B. nigra. The results disclosed two strongly supported clades, one containing four accessions of vegetable mustard which have closer relationship with B-genome species “B.nigra” lineage and the other containing 12 accessions of B. juncea and three A-genome accessions. This classification was in disagreement with the evidence from chloroplast DNA, mitochondrial DNA, nuclear DNA restriction fragment length polymorphism (RFLP), which suggested that B. juncea was closely related to the A-genome type. For the incongruence, we speculated that the B. juncea crops derived from Chinese have evolved through different recombined events of the diploid morphutypes and evolved unidirectional concerted evolution. The traditional phenotypic classification of B. juncea was not wholly supported by ITS results, and hence the phylogenetic relationships among these subspecies need to be reconsidered on molecular level.     

The combined effects of enhanced UV-B radiation and selenium on growth, chlorophyll fluorescence and ultrastructure in strawberry (Fragaria × ananassa) and barley (Hordeum vulgare) treated in the field

The possible ameliorative effects of selenium (Se) addition to soil on the detrimental effects of enhanced UV-B radiation were tested on strawberry and barley during 4 months of field experiment in Kuopio, Central Finland. Control plants were exposed to ambient levels of UV radiation, using arrays of unenergized lamps. A control for UV-A radiation was also included in the experiment. Added Se, applied as H₂SeO₄, at the level of 0.1 mg kg⁻¹ soil (low dosage) and 1 mg kg⁻¹ soil (high dosage) increased Se concentrations in plants more than 10 and 100 times, respectively. After 4 months of exposure, strawberry and barley plants were harvested for biomass analysis. Chlorophyll fluorescence was measured using the Hansatech FMS2 fluorescence monitoring system. Leaf anatomy and ultrastructure were observed by light and transmission electron microscope. Several effects of UV and Se as well as their interaction were found, mostly for strawberry, but not for barley, indicating species-specific responses. Our results provided evidence that the high Se concentration in soil had no ameliorative effect but increased the sensitivity of strawberry to enhanced UV-B radiation in the field. Under ambient radiation, Se did not alter leaf growth of strawberry, whereas under UV-B radiation, the high Se addition significantly decreased leaf growth. Strawberry runner biomass was affected by the interaction of Se and UV. Under ambient radiation Se did not change dry weight of runners, but in combination with UV-A or UV-B radiation the high Se dosage decreased dry weight of runners by about 30%. Although the high Se concentration positively influenced on quantum efficiency of photosystem II (PSII) in strawberry leaves, it reduced runner biomass, leaf number and ratio of starch to chloroplast area. This suggests that the harmful effects of the high Se dosage on photosynthetic processes occurred as a result of changes in activity or/and biosynthesis of enzymes, rather than alteration of PSII. At the low concentration, Se effects were slight and variable.Although barley leaves accumulated higher Se concentrations than strawberry, there were no apparent changes in their growth, biomass or chlorophyll fluorescence due to Se effect either alone or in combination with UV-B. However, at the ultrastructural level, an enlargement in the peroxisome area was found due to combination of UV radiation with Se, suggesting the activation of antioxidative enzymes, possibly catalase. Decrease in mitochondrial density in barley cells in response to Se might be attributed to alteration of mitochondrial division. Increase in the proportion of cells with cytoplasmic lipid bodies due to combined effect of UV-B and Se indicated the alteration of lipid metabolism and the acceleration of cell senescence in barley. Main UV-B effects were found, mostly at the tissue and ultrastructural level in strawberry, but not in barley, indicating species-specific susceptibility to enhanced UV-B radiation. UV-B-treated strawberry plants developed marginally thinner leaves with reduced ratio of starch to chloroplast area in their cells, suggesting negative influence of UV-B on photosynthetic processes.     

Oleaster (var. sylvestris) and subsp. cuspidata are suitable genetic resources for improvement of the olive (Olea europaea subsp. europaea var. europaea)

The olive belongs to Olea, a complex genus and to a species with six subspecies. Subsp. europaea includes both the cultivated olive and the oleaster, the wild ancestor of the olive. Little is known on the phenotype of fruits from subsp. cuspidata. We aimed to compare europaea and cuspidata trees for oil content and composition and to verify whether natural hybrids may exist between the two subspecies. Specimens were from Kenya and putative natural hybrids between cuspidata and europaea were from Stellenbosch (South Africa). Cultivar and oleaster trees were sampled in France (continental and Corsica), Italy (Continental and Sardinia) and Tunisia. We have examined the fruit (drupe) structure between subsp. cuspidata and europaea and extracted oil from the pulp, seed and total drupe. Comparison for oil content was made between the cultivated olive and the oleaster and some cuspidata trees from Kenya. A few of cuspidata individuals from Botanical gardens do not enable phenotyping for oil content and composition. Oil composition analyses were performed for the main fatty acids to compare the three taxa. We used microsatellite markers at 11 loci to compute genetic distances between cuspidata, oleaster and cultivar trees and to reveal eventual hybrids. The SSR polymorphisms were huge between the two subspecies and they revealed that putative hybrids were true hybrids sampled around olive orchards. The whole comparison of oil content shows that olive cultivars display higher oil content than the subsp. cuspidata and that the oleaster trees are intermediate, whereas for oil composition of the drupe, cuspidata from Kenya shows less oleic acid than europaea. However, the cuspidata trees show seed oil composition similarities with the other two taxa. The discussion deals with possible reasons to explain the differences and of the possible uses of these taxa for breeding both the olive and brown olive. H. Hannachi and H. Sommerlatte have equal contribution in the article.     

Responses of co-occurring populations of Dendrobaena octaedra (Lumbricidae) and Cognettia sphagnetorum (Enchytraeidae) to soil pH, moisture and resource addition

Dendrobaena octaedra (Lumbricidae) and Cognettia sphagnetorum (Enchytraeidae) are the two most dominating soil invertebrates in terms of biomass in boreal coniferous forest soils. A microcosm experiment was set up in order to study the influence of pH, moisture and resource addition on D. octaedra and C. sphagnetorum when both species are simultaneously present. Two kinds of coniferous forest humus were used as substrate, pine stand humus (pH 4.2), and spruce stand humus (pH 4.6); in the third treatment the pine stand humus was adjusted with slaked lime (CaOH₂) to the same initial pH as the spruce stand humus. Each substrate was adjusted to water contents of 25%, 42.5% and 60% of WHC (referred to as ‘dry’, ‘moist’ and ‘wet’). In the second part of the experiment, spruce needle litter and birch leaf litter were separately added into the pine stand humus (‘moist’, unlimed) and compared with a control without litter. The microcosms were plastic jars with 75 g (d.m.) of humus, into which 4 specimens of D. octaedra and 70 specimens of C. sphagnetorum were added. D. octaedra showed the highest biomass and C. sphagnetorum the lowest biomass in the spruce stand humus with higher pH. Moisture did not affect earthworms, while C. sphagnetorum thrived best at the highest moisture. Addition of both kinds of litter increased the numbers and biomass of D. octaedra, while on C. sphagnetorum resource addition had little effect. The results help to explain the abundance of these two species in coniferous forests differing in soil acidity, moisture and fertility.     

New sources of resistance to race Ro1 of the Golden nematode (Globodera rostochiensis Woll.) among reputed duplicate germplasm accessions of Solanum tuberosum L. subsp. andigena (Juz. et Buk.) Hawkes in the VIR (Russian) and US Potato Genebanks

Cultivated Solanum tuberosum L. subsp. andigena is well known as a rich source of valuable traits for potato breeding, especially for resistance to diseases and pests. The golden potato cyst nematode, Globodera rostochiensis Woll., is considered to be one of todays most serious hindrances to potato production in Europe and North America. Thus, the breeding of new cultivars that have resistance to PCN is of great importance. The USPG (USA) and VIR (Russian) potato genebanks, as well as others, maintain many samples of primitive cultivated and wild potato species originating from Latin America. Many of these samples are assumed to be genetically duplicated because the material in both genebanks came from the same original source. A joint investigation of new genotypes of subsp. andigena forms resistant to potato cyst nematode (PCN) was carried out on samples of subsp. andigena at VIR with reputed duplicate samples at USPG. After careful screening, 14 samples which possessed resistance to PCN were identified. A high level of this resistance was transmitted to sexual progeny at a high frequency for all of the selections. Eleven of the accessions found to be resistant have reputed duplicates in USPG that were not previously known to be resistant. Thus, this research not only broadens the choice of parents available for resistance breeding, but identifies model materials for future research to test the parity of PCN resistance among reputed duplicate samples in the two genebanks.