Evidence for inbreeding depression in the food-deceptive colour-dimorphic orchid Dactylorhiza sambucina (L.) Soò

About one third of all orchid species are deceptive, i.e., not providing any reward to their pollinator. Such species often have lower visitation rates compared to rewarding relatives. This could result in lower levels of geitonogamous selfing and thus would provide an advantage in term of progeny fitness through inbreeding avoidance. This hypothesis could be tested by comparing the level of inbreeding depression between deceptive and rewarding orchids. However, due to the difficulty to raise orchids from seeds, few studies of inbreeding depression are available, and most are focused on very early life stages, such as seed mass or embryo viability. Here, we present the results from an experimental investigation of inbreeding depression in the deceptive flower-colour dimorphic Dactylorhiza sambucina, from in vitro cultivation to greenhouse soil transplantation. We found strong inbreeding depression at all recorded stages (i.e., germination and survival), with estimates ranging from 0.47 to 0.75. Our study finally proposes a simple and suitable experimental protocol to raise orchids from seeds with high germination rates.     

Evidence of post-pollination barriers among three colour morphs of the deceptive orchid Dactylorhiza sambucina (L.) Soó

Floral-colour polymorphism in rewardless orchids has been hypothesized to be maintained by means of naïve insects, which after visiting a flower without reward will tend to fly elsewhere, looking for a flower of a different colour. In this study, levels of male and female reproductive success were monitored in Southern Italy populations of the deceptive orchid Dactylorhiza sambucina, through field observations over 3 years. These populations were characterized by the presence of a rare pink morph which is sympatric with the more frequent yellow and red morphs. In addition, final plant fertility was evaluated through percentages of embryo-containing seeds produced in both natural conditions and hand-pollination experiments. Results showed that pollinator preferences were independent of the morph frequencies and thus do not promote the predicted negative frequency-dependent selection. Although yellow and pink morphs showed significantly higher male reproductive success (RS), we found comparable levels of female RS, which suggest that pollinator behaviour cannot be the main mechanism which maintains this polymorphism. Interestingly, we found different percentages of embryo-containing seeds in fruits set under natural conditions as well as in those obtained from experimental crosses. In particular, pink morph showed a very low intrinsic fertility. Moreover, fertility in intra- was higher than in inter-morph crosses. To our knowledge, this is the first study pointing out the occurrence in the orchid family of post-pollination reproductive barriers. Findings are discussed in light of present hypothesis on the evolution and maintenance of colour polymorphism in deceptive orchids and other angiosperms.     

Are pollinators the agents of selection on flower colour and size in irises?

Plant–pollinator interactions are believed to play a major role in the evolution of floral traits. Flower colour and flower size are important for attracting pollinators, directly influencing reproduction, and thus expected to be under pollinator‐mediated selection. Pollinator‐mediated selection is also proposed to play a role in maintaining flower colour polymorphism within populations. However, pigment concentrations, and thus flower colour, are also under selective pressures independent of pollinators. We quantified phenotypic pollinator‐mediated selection on flower colour and size in two colour polymorphic Iris species. Using female fitness, we estimated phenotypic selection on flower colour and size, and tested for pollinator‐mediated selection by comparing selection gradients between flowers open to natural pollination and supplementary pollinated flowers. In both species, we found evidence for pollen limitation, which set the base for pollinator‐mediated selection. In the colour dimorphic Iris lutescens, while pigment concentration and flower size were found to be under selection, this was independent of pollinators. For the polymorphic Iris pumila, pigment concentration is under selective pressure by pollinators, but only for one colour morph. Our results suggest that pollinators are not the main agents of selection on floral traits in these irises, as opposed to the accepted paradigm on floral evolution. This study provides an opposing example to the largely‐accepted theory that pollinators are the major agent of selection on floral traits.     

Effects of the planting density on water relations and production of ‘Chemlali’ olive trees (Olea europaea L.)

Water relations are a key factor limiting olive production. In this study, effects of plating density on physiological aspects and productivity of ‘Chemlali’ olive trees were analyzed under rain-fed conditions in four planting densities (156, 100, 69 and 51 trees ha⁻¹), in an experimental olive orchard located in the center of Tunisia. Seasonal changes in leaf relative water content (RWC), leaf water potential, stomatal conductance (g _s), CO₂ assimilation rate and tree production were studied. Accompanying the changes in leaf water status, all the monitored trees reduced leaf stomatal conductance (g _s) and photosynthetic rate (A) throughout the summer drought, mirroring the increase in soil moisture deficit and vapor pressure deficit. However, the decrease in gas exchange was much more pronounced in high planting densities than in low ones. Our results confirm that the increase of tree-to-tree water competition with planting density was significant in the dry climate of Tunisia. Thus, planting density is critical when planting new olive orchards in arid regions.     

On the monophyly of Dactylorhiza Necker ex Nevski (Orchidaceae): is Coeloglossum viride (L.) Hartman a Dactylorhiza?

Previous phylogenetic analyses of Orchidaceae subtribe Orchidinae resulted in the proposal to classify Coeloglossum viride (L.) Hartman within the genus Dactylorhiza in order to maintain its monophyly. In this paper, we report some results that contradict previous studies regarding the monophyly of the traditional Dactylorhiza and its phylogenetic relationship with Coeloglossum. Our results, which combine sequences of the internal and external transcribed spacers of the nuclear ribosomal DNA, support the monophyly of Dactylorhiza , with Coeloglossum being a sister clade. The position of C. viride in the phylogenetic tree, and the considerable morphological differences with respect to Dactylorhiza , incline us to retain both lineages as distinct genera.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 152 , 261–269.     

The effect of local heating on the calls of the fire—Bellied toad,Bombina Bombina (L.)

In order to determine where the characteristic temperature-dependent changes in calling rate, call duration and fundamental frequency of the call of the fire-bellied toad originate, I heated the head and other parts of the body to various temperatures. The greatest increase in calling rate occured when the head was heated; it varied with the amount of heating. The changes in calling rate and call duration brought about by heating were equally rapid, whereas the frequency of the call increased more slowly. This suggests that both calling rate and call duration change as a direct result of the effect of heat upon the nervous system.     

Effects of photoperiod and of ultraviolet radiation on the incidence of diapause in the Horn Fly, “Haematobia Irritans (L.) (Diptera: Muscidae)”

The horn fly, HAEMATOBIA IRRITANS (L.), is a bloodsucking pest of cattle found in almost all cattle-raising areas of the northern hemisphere.Predisposition to diapause in the pupal stage was determined in the adult parent. The predisposition was influenced by photoperiod which may have its effect either directly on the insect or indirectly by influencing the host blood. The percentage of the pupae that entered diapause varied inversely with the length of the photoperiod between 12 and 20 hours. Light in the visible range (7,800 to 4,000 A.U.) was provided byCool-whitefluorescent tubes. The addition of ultraviolet radiation (3,900 to 2,800 A.U.) in the 16- and 20-hour photoperiods further decreased the percentage of diapause.

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Zusammenfassung Die Hornfliege, HAEMATOBIA IRRITANS (L.), ist ein blutsaugender Parasit in fast allen Rinderzuchtgebieten der nördlichen Hemisphäre.Die Prädisposition zur Diapause im Puppenstadium wurde in den erwachsenen Eltern determiniert.Sie wurde durch Belichtung beeinflusst, die entweder direkt auf das Insekt oder indirekt über das Blut des Wirtes wirkte. Die Prozentzahl an Puppen in Diapause fiel ab, wenn die periodischen Belichtungszeiten von 12 bis 20 Stunden verlängert wurden. Das sichtbare Licht (7800–4000 Å) stammte von cool-white fluoreszierenden Röhren. Durch die periodische Zugabe einer Ultraviolett- (3900 – 2800 Å) Bestrahlung fiel der Anteil an Diapausen noch weiter.

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Résumé La mouche, HAEMATOBIA IRRITANS (L.), est un parasite hématophage du bétail répandu dans presque toutes les zones d'élevagê de l'hémisphère nord. La prédisposition à la diapause au stade de pupe a été déterminée chez les parents adultes. La prédisposition est influencée par une période d'éclairage qui peut agir soit directement sur l'insecte soit indirectement par l'intermédiaire du sang de l'hôte. Le pourcentage des pupes entrant en diapause varie inversement à la durée d'un éclairage de 12 à 20 heures. La lumière blanche (7800 – 4000 Å) est produite par des tubes fluorescents froids. L'addition de rayonnement ultra-violet (3900 à 2800 Å) dans les périodes d'éclairage de 16 et de 20 heures réduit encore le pourcentage de diapauses.

     

Effects of Shading on the Synthesis of Volatile Organic Compounds in ‘Marselan’ Grape Berries (Vitis vinifera L.)

Journal of Plant Growth Regulation - Light is a vital environmental factor that can affect the synthesis of volatile organic compounds (VOCs) in grape berries. However, the mechanism through which...     

Effects of insecticide applications on macroinvertebrate density and biomass in rice-fields in the Rhône-delta,France

The density of 23 macroinvertebrate species and the total macroinvertebrate biomass were compared between rice-fields treated with lindane and diazinon in June and alphamethine in August and untreated controls. The macroinvertebrates could be divided into four groups: (1) Taxa, in which the densities were lower in the insecticide treatment in July and August than in the non-insecticide treatment. (2) The Culicidae which occurred in the insecticide treatment in significantly lower density in July, but in significantly higher density in August. (3) Ischnura elegans (Vander L.) which was found in July after the lindane application in significantly higher numbers in the insecticide treatments, but in significantly lower numbers in the insecticide treatment in August after the application of the pyrethroid. In these three groups, we assumed that direct effects due to the insecticides toxicity were the reason for the differences in density. (4) The fourth group included three taxa in which the densities were significantly higher in the insecticide treatment in July and August than in the control. For this, indirect effects due to reduced biotic interactions may be responsible. The biomass was higher in the insecticide treatments in July, mainly because of a high increase in gastropod density, during the rest of the season it was similar between treatments and controls.     

Stomatal density distribution patterns in leaves of the Jatobá (Hymenaea courbaril L.)

Stomata are leaf structures that are essential for regulating gas exchange and water balance in terrestrial plants. Accurately quantifying stomatal characteristics is consequently of great importance for understanding the physiological processes of plants under different environmental conditions. The objective of this study was to investigate the spatial distribution pattern of stomata on leaflet surfaces, and the possible mechanisms that influence this pattern, particularly leaf expansion. To achieve this, we used geostatistical tools combined with an analysis of biometric relationships of leaves from Hymenaea courbaril L. Our analysis indicates that stomata show a clear spatial structure in this species: average values of foliar expansion rates (ERs) were different on right and left-hand sides of the primary venation of each leaflet and there was a close relationship between the spatial pattern of stomatal density and leaf expansion rate. Such differences in lateral expansion may therefore be partially responsible for the heterogeneous distribution of stomata documented here and in other studies.     

Isozyme polymorphism and genetic structure of the population of Sorbus torminalis (L.) Crantz from the Bytyń Forest (Poland)

Dormant buds collected from 35 wild service trees (Sorbus torminalis) in the Bytyń Forest were tested with horizontal gel electrophoresis to assess the genetic structure of the population. Among 16 investigated isozyme loci, seven loci (ADH-A, 6PGD-A, GDH-B, ME-A, SOD-A, PGM-A, PGM-B) proved to be polymorphic, whereas the other nine loci (SDH-A, SDH-B, DIA-C, DIA-D, FLE-A, FLE-B, GOT-B, IDH-A, IDH-B) were monomorphic. The number of alleles per polymorphic locus ranged from two to three, with a mean of 2.29. The average observed and expected heterozygosities were 0.2665 and 0.3462, respectively. The combined FIS value over all polymorphic loci was 0.2179, which reflects a substantial deficit of heterozygotes. Two polymorphic loci (SOD-A, PGM-A) were identified in S. torminalis for the first time.     

Effects of the “Aegean Sea” oil spill on biotransformation enzymes,oxidative stress and DNA-adducts in digestive gland of the mussel (Mytilus edulus L.)

Possible molecular biomarkers of impact by organic pollution on mussels were applied to samples from five sites along the Galician Coast, Spain, taken 6 months after the oil spill from the tanker “Aegean Sea.” Whole body aliphatic hydrocarbon concentrations were similar at all sites, but specific chemical ratios (resolved/unresolved hydrocarbons; carbon preference index; pristane/phytane) indicated a predominance of degraded petrogenic hydrocarbons nearer the oil spill. Levels of whole body polycyclic aromatic hydrocarbons (sum of 13 PAHs) increased steadily towards the oil spill, and were paralleled by increases in digestive gland levels of total cytochrome P-450, CYP1A-like protein and lipid peroxidation (corr. coeffs. with PAHs of 0.64–0.67). Differences were more marked in CYP1A-like protein than total cytochrome P450, indicating induction of specific P450 isoenzyme(s). No differences between sites were seen for benzo[a]pyrene hydroxylase, glutathione S-transferase, Superoxide dismutase and DT-diaphorase activities. Bulky, hydrophobic DNA-adducts were detected in digestive gland of mussels from industrial and urban sites, but not from the site nearest to the oil spill which had the highest tissue levels of PAHs. Overall the results indicate induction of cytochrome P450(s) and oxidative damage in mussel with oil exposure.     

The Fine Structural Observation on the Development of Embryo and Endosperm in the Intergene- rfc Crosses of Fadish ♀ (Raphanus sativus L.) Cabbageo ♂ (Brassica oleracea L.)

The present report deals with the structural abnormalities and abortion of the endosperm, and the related abnormal development of the embryos in the intergeneric crosses of radish (Raphanus sativus L.) ♀ with cabbage (Brassica oleracea L.) ♂. The weak development of ER, the occurence of starch grains in chloroplasts, the curious distribution of chloroplasts around the nuclei, and the earlier formation of cellular endosperm are some primary structure abnormalities of endosperm and they may indicate the poor development, low metabolic activities, and precocious growth in the hybrid endosperm. The endosperm abortion, which starts from chalazal end endosperm, comprises the damage of both structure and function of ER membrane, and the disintegration of nuclei and organelles, or even death. The hybrid embryos degenerated very early in 2-cell stage or even zygote stage in case the endosperm Aborted early. In case of endosperm late-aborted, the hybrid embryos grew for quite a long period of time but become slow down as the endosperm showed abnormal development and started to abort. As the results, the embryos were smaller, the embryo propers and the suspensors showed no growth in step with one another, and the embryo cells appeared structural abnormalities, and finally degenerated and aborted.     

“Stress” reactions in teleosts: Effects of temperature and activity on anaerobic energy production in roach (Rutilus rutilus L.)

• 1.1. In roach any kind of excitement due to swimming, handling, or to unfavourable environmental conditions, is reflected in an increase of lactate above 1.0 μ mol and a decrease of phosphocreatine (PCr) below 15.0 μ mol g⁻¹ in the muscles.
• 2.2. In fish acclimated to and tested at 4°C lactate accumulation and PCr hydrolysis after activity were only half those in fish tested at 12 and 20°C.
• 3.3. Fish swimming at submaximal speed for 60 min at 20°C had much less lactate in the anterior body musculature than fish swimming for the same length of time at 12°C.
• 4.4. It is suggested that the “sudden death syndrome” of severely exercised fish is due to rapid hydrolysis of PCr, rather than to acidosis, in sensitive tissues.

     

Effects of benomyl on reproduction and population structure of enchytraeid oligochaetes (Annelida)—Sublethal tests on agar and soil

• 1.1. The toxicity of the fungicide benomyl to terrestrial enchytraeid species was tested under different conditions.
• 2.2. Despite a relatively low acute response even to higher concentrations in agar media, sensitive effects were observed for cocoon production and hatching success at the recommended concentration for agricultural application (5.9 ppm in the test medium).
• 3.3. These sublethal effects could be reconciled with population tests in larger quantities of soil: lower abundance was due to a very low number of juveniles in the benomyl-treated cultures.