Variation in expression of trimorphic incompatibility in Pontederia cordata L. (Pontederiaceae)

Summary Pontederia cordata L. (Pontederiaceae), a perennial diploid, possesses the rare genetic polymorphism tristyly. A controlled pollination programme was conducted over a three year period, under glasshouse conditions, on 36 clones of P. cordata var. cordata to examine the nature of the self-incompatibility system. The three major findings of the pollination study were: (1) the three floral morphs display different levels of self-incompatibility, (2) pollen from the two anther levels within a flower exhibits different compatibility behaviour in self-pollinations, (3) considerable individual genetic variation in the expression of self-incompatibility is evident among clones within floral morphs. Similar results were also obtained from a smaller study on 15 clones of P. cordata var. lancifolia conducted over a 6 month period. In common with other Pontederia species the mid-styled morph (M) of P. cordata produces large amounts of seed when self-pollinated with pollen from long-level anthers. A developmental model is proposed to explain the high level of self-compatibility of the M morph in Pontederia species. Self-pollination of segregating progenies from M and S morphs of known incompatibility status demonstrated that the expression of incompatibility is closely associated with style length. It is suggested that overall differences in incompatibility behaviour among the floral morphs may be due to the pleiotropic effects of major genes controlling sub-characters of the tristylous syndrome, rather than linked modifier genes. However, the variable expression of trimorphic incompatibility within floral morphs suggests that this variation may be polygenic in origin.     

Pollinator foraging behavior and pollen collection on the floral morphs of tristylous Pontederia cordata L.

Summary The foraging behavior of the pollinators of tristylous Pontederia cordata was studied to determine if differences in floral morphology would lead to preferential visitation of the floral morphs. Although nectar production is not different in the three floral morphs, differences in the production and size of pollen grains produced by the three anther levels results in the morphs offering variable amounts of resources to pollen-collecting insects. Bumblebees (Bombus spp.) and the solitary bee Melissodes apicata used P. cordata primarily as a nectar source and therefore did not seem to exhibit any morph preference. In contrast, honeybees visited flowers mainly for pollen and preferred to forage on long-level anthers of the short-and mid-styled morphs. An analysis of the composition of corbicular pollen loads indicated that, relative to the frequency of production in the population: 1) honeybees collected an excess of pollen from long-level anthers; 2) bumblebees collected the three types of pollen without any apparent preference; and 3) M. apicata preferentially collected pollen from the short-level anthers — presumably because their proboscides are modified by the presence of tiny hairs. The results suggest that P. cordata in Ontario is serviced by a diverse, unspecialized pollinator fauna which is not co-adapted to the tristylous floral polymorphism.     

A test of spatial memory and movement patterns of bumblebees at multiple spatial and temporal scales

Naive bumblebee foragers appear to use movement rules at smallspatial and temporal scales, but it is not clear whether theserules determine movement patterns as the scales increase. Onestrategy for efficient foraging used by bumblebees is near-farsearch, involving short flights when in good patches of flowersand longer flights when in poor patches. Bumblebees also demonstratethe use of a spatial memory strategy by returning repeatedlyto patches of flowers, and even following the same route betweenflowers, over periods of days. We attempted to determine atwhat spatial scales bumblebees use spatial memory while foragingwithin a patch and after how many flower visits spatial memoryoutweighs near-far search. Bumblebees in the laboratory foragedon a 4 x 4 array of artificial flowers with distances rangingfrom 10 to 80 cm between flowers in two simple spatial patterns.The proportion of visits to flowers containing a sucrose rewardwas monitored for either 100 or 400 flower visits in two separateexperiments, after which the locations of the rewarding andnonrewarding flowers were interchanged, producing a mirror image.A drop in accuracy after the mirror image switch would indicatethat the bees had memorized the location of rewarding flowers.Mirror image tests, and comparisons to a simulation model ofnear-far search based on actual flight distances, indicate thatnaive bumblebees used near-far search on flowers 10 cm apartbut increasingly used spatial memory as experience and spatialseparation increased. Bumblebees thus have multiple tacticsavailable to forage efficiently in different environments.     

Patterns of resource use,food quality,and health status of voles (Microtus pennsylvanicus) trapped from fluctuating populations

Summary Recent studies suggest that diet quality is responsible for differential survivorship of vole cohorts (Boonstra and Boag 1987) and spacing behavior of females (Ims 1987). These phenomena have been related either to a lack of or a deterioration in the quality of the preferred food. To test this hypothesis, we compared foods habits, food quality and health status of meadow voles (Microtus pennsylvanicus) from high and low population density phases. In this study, seven plant species represented the main food items used on a regular basis and biomass values of preferred species decreased with browsing pressure. In addition, food quality of the main dietary items changed between phases forcing females to adjust their feeding strategy accordingly. Health of voles changed also opening the way to speculations on competition for high quality food resources and survivorship.     

Kinetics of larval gregarious behavior in the bark beetleDendroctonus micans (Coleoptera: Scolytidae)

This paper provides a simple mathematical model of the aggregation behavior of the gregarious intracortical-feeding larvae of the bark beetle, Dendroctonus micans. The model's assumptions are that each individual produces pheromones at a constant rate and reacts positively to a pheromone gradient. These hypotheses have been tested by comparing experiments and simulations, both of which showed that (1) homogeneously distributed individuals aggregate rapidly at the center of the experimental or theoretical arena and (2) eccentric, preformed groups succeed in attracting dispersed individuals, provided that the initial size of these groups is sufficiently high. There is good agreement between most of the experimental and theoretical results, providing a link among chemical communication, density of larvae, and random events occurring during the development of a spatial structure.     

Contrasting movement patterns of nectar-collecting and pollen-collecting bumble bees (Bombus terricola) on fireweed (Chamaenerion angustifolium) inflorescences

Abstract. 1. Movements of nectar and pollen-foraging bumble bees on inflorescences of Chamaenerion angustifolium (L.) J. Holub (fireweed or rosebay willow herb) were compared with predictions based on reward distributions and optimality principles. Observations suggest that nectar and pollen-gathering bumble bees behave according to the same set of reward maximization criteria when foraging from flowers of this species.
2. Both kinds of foragers matched their arrival points with the vertical positions on inflorescences in which the densities of their respective food resources were greatest. For nectar-foragers, this point was located at the lowest tier of flowers, whereas for pollen-foragers it was found in the middle of the inflorescences. Nectar and pollen-foraging bees both moved upward on inflorescences following gradients from high to low reward availability.
3. Nectar-foragers responded to decreases in inflorescence size over the season by reducing the number of flower visits made on each raceme. Number of flowers visited by pollen-foragers was low throughout and reflected the scarcity of male-phase flowers on racemes. Flower revisitation rates were low for both kinds of workers, but were slightly higher for those collecting pollen.     

The role of lignin as a defence against the spruce bark beetle Dendroctonus micans: effect on larvae and adults

Summary The role of lignin as a physical defence against Dendroctonus micans was investigated in laboratory feeding experiments. The effect of lignin is dose-dependent, reducing larval survival, growth rate, and weight, as well as affecting gallery construction. Adults lay fewer eggs in lignified bark and also tend to construct abnormal galleries. The distribution of lignin in trees suggests a role in defence against bark beetles that feed in the thicker bark on the lower bole.     

The use of spatial cues for structural guideline orientation inTapinoma sessile andCamponotus pennsylvanicus (Hymenoptera: Formicidae)

Camponotus pennsylvanicus(DeGeer) and Tapinoma sessile(Say) exploit structural elements as guide-lines in their topographic orientation. This research documents the response of T. sessileand C. pennsylvanicusto a series of thigmotactic, gravitational, chemotactic, and phototactic cues while utilizing structural guidelines. Adherence to these guidelines is more pronounced on vertical than on horizontal surfaces and more pronounced in darkness than in daylight. Orientation switches from a crestline on the horizontal to a groove on the vertical. Light and odor trails serve an important role as distance cues in structural guideline orientation. The hierarchy of orientation cues and the adaptive significance of these ant's exploitation of structural guidelines are discussed.     

Anatomical study of zygotic and somatic embryos of Tilia cordata

A comparative anatomical study was carried out on zygotic and somatic embryos of Tilia cordata Mill. to evaluate the effect of growth conditions on their development. Zygotic embryos (heart-shaped, torpedo, cotyledonary), collected during two autumn periods, were examined to investigate the effect of growing season on embryo development. In comparison, the influence of growth conditions on the development of somatic embryos in vitro was also studied. Treatment with abscisic acid (ABA) and polyethylene glycol-4000 induced the development of somatic cotyledonary embryos similar to zygotic embryos with respect to morphology and anatomy, as illustrated by the differentiation of the apical meristems and of the procambium. The pattern of accumulation of starch and protein was also similar in these embryos. Somatic cotyledonary embryos that developed spontaneously without ABA showed defective accumulation of storage material and a general failure to form the shoot apical meristem, leading to very low germination rates. Vacuolar phenolic deposits were observed along the procambium of both zygotic and somatic embryos regardless of the maturation stage. Tracheid formation was observed only in somatic embryos formed without ABA in the medium and in precociously germinated somatic embryos. Phenolic vacuolar inclusions were frequently observed in epidermal cells of these embryos. This revised version was published online in June 2006 with corrections to the Cover Date.     

The first study on the bacterial flora of the european spruce bark beetle, Dendroctonus micans (Coleoptera: Scolytidae)

The European spruce bark beetle, Dendroctonus micans Kugelann (Coleoptera, Scolytidae), is one of the most serious pests of oriental spruce (Picea orientalis L.) in Turkey. In this study, we investigated bacterial flora of D. micans collected from different populations of the forests of Eastern Black Sea Region of Turkey from 2002 to 2004. Seven different bacteria were isolated from healthy, diseased and dead specimens based on the color of colony and morphology. According to morphological, physiological and biochemical properties, metobolic enyzme profile by BIOLOG microtiter plate system, and total cellular fatty acid profile by Microbial Identification System (MIS), isolates were identified as Micrococcus luteus, Bacillus thuringiensis subsp. morrisoni, Serratia grimesii, Enterobacter cloaceae, Enterobacter intermedius, Streptococcus sp. and Pseudomonas putida. This is the first study on the bacterial flora of D. micans.     

不同生境鱼腥草形态特征及主要有效成分含量差异分析

以不同生境中的鱼腥草为研究对象,分析其形态特征及主要有效成分含量的差异。该文测定了不同生境下主要环境因子指标及鱼腥草的叶长、叶宽、株高、基径、生物量和含水量,用高效液相色谱法测定其各部分主要有效成分金丝桃苷、槲皮苷含量,并对测量结果进行单因素方差分析和相关性分析。结果表明:环境因子会对鱼腥草的形态建成及有效成分积累造成不同影响,适宜的光照强度有利于鱼腥草对有效成分的累积;鱼腥草中有效成分的含量表现出叶茎根的规律。适宜的遮阴处理,既可避免强光照对鱼腥草生长的抑制,又可显著提高有效成分的含量,从而整体增加对鱼腥草有效成分的收益。     

Anthocyanin production in cultured cells of Aralia cordata Thunb.

High anthocyanin-producing cell lines, which were grown in a dark or in a light-dark regime, were selected from callus cultures initiated from stem and leaf tissues of Aralia cordata Thunb. by small-cell-aggregate selection. To verify the optimum culture conditions for anthocyanin production, cells were tested by changing the various basal media, sucrose concentration and nitrogen source and concentration. Good growth was obtained in the dark on Linsmaier-Skoog's basal medium containing 1.0 mg l^-1 2,4-d and 0.1 mg l^-1 kinetin, 2% (w/v) sucrose and full strength of nitrogen concentration. However, the highest anthocyanin yield (10.3% dry wt) was obtained in the dark on B5 medium containing 1.0 mg l^-1 2,4-d and 0.1 mg l^-1 kinetin. Our results suggested that it has became feasible to find the most effective conditions for cell growth and anthocyanin production by optimizations of the nitrogen concentration and the ratio of NH₄ ⁺ to NO₃ ^- in the medium.Abbreviations B5 Gamborg (Gamborg et al. 1968) - 2,4-d 2,4-dichlorophenoxyacetic acid - LS Linsmaier and Skoog (Linsmaier & Skoog 1965) - MS Murashige and Skoog (Murashige & Skoog 1962) - NN Nitsch and Nitsch (Nitsch & Nitsch 1967) - WH White (White 1963) This paper is part 81 in the series Studies on Plant Tissue Cultures. For Part 80 see Furuya T, Sakamoto K, Iida K, Asada Y, Yoshikawa T, Sakai S & Aimi N (1992) Phytochemistry 31: 3065–3068.     

High-frequency induction of multiple shoots and clonal propagation from rhizomatous nodal segments of Houttuynia cordata Thunb.—An ethnomedicinal herb of India

Summary This study reports an efficient and direct shoot bud differentiation and multiple shoot induction from nodal segments of underground stoloniferous rhizomes of Houttuynia cordata Thumb. The frequency of shoot bud regeneration was influenced by the type of cytokinin and concentrations. Among the various concentrations used, benzylaminopurine (BAP, 17.74 μM) or kinetin (Kn, 18.58 μM) was found to be most effective for rapid and maximum shoot but differentiation. The number of shoots per explant was higher (20.00±2.61) on Murashige and Skoog (MS) medium supplemented with Kn (18.58 μM) compared to BAP and 6-γ-γ-(dimethyl-allylamino)-purine (2iP) during initial 40-d-old culture. Subsequent shoot differentiation and multiplication were achieved in MS medium containing 9.29 μM Kn and 15% (v/v) coconut milk. Elongation and growth of multiple shoots were also obtained on MS medium containing either 2.32 μM Kn or 2.46 μM 2iP alone. The rate of shoot multiplication during subcultures declined with an increase in the size of proliferating shoot cluster. Reducing shoot cluster size to three to four shoots and subculturing together in shoot multiplication medium resulted in a better shoot multiplication and growth, which could be maintained for 2 yr. The elongated shoots (>20 mm) were successfully rooted on MS medium supplemented with 19.60 μM indole-3-butyric acid. Regenerated plants were successfully established in soil and were found to be healthy and uniform. The protocol reported in this study can be used for conservation and utilization of elite clone of H. cordata.     

Variation of ommatidia number as a function of worker size inCamponotus pennsylvanicus (DeGeer) (Hymenoptera: Formicidae)

Summary The relation of worker size to ommatidia number was examined in the polymorphic antCamponotus pennsylvanicus (DeGeer). Linear regression described this relationship as:Y = 260.9 + 113.6×; whereYis ommatidia number andX is head width. A log-log regression described this relationship as:Y = 323.5 + 286.9*logX(r ² = 0.98). This analysis indicated an allometric relation of ommatidia number to head width, where ommatidia numbers increase at a slower rate than head width. This relationship is discussed in terms of ethotypes associated with worker morphotypes, and the possible mechanisms regulating polymorphic development.     

Summer biomass of a population of Iridaea cordata (Gigartinaceae,Rhodophyta) from Antarctica

Results of a seasonal study on biomass in an infralittoral population of Iridaea cordata from Terra Nova Bay (Ross Sea, Antarctica) are reported. Thalli were collected during the IX Italian Antarctic Expedition (austral summer 1993–94). The population studied is that living at depths of 4 to 6 m, where the highest density of plants occurred. The highest value of biomass (wet weight 3440 g m^–2) was found at the beginning of summer. In that period 72.5% of biomass was from 128 specimens belonging to weight classes 8 (>16 to 32 g) to 10 (>64 g), corresponding to 13.4% of the population in numbers. Small (<1 g) and medium (1 to 8 g) specimens provided the remaining biomass of 5% and 22.5%, respectively. During the month of January, the number of heavy specimens decreased. At the end of that month biomass reached a minimum of 2225 g m^–2. In February the biomass increased to 3169 g m ^–2, 72% of which was from 120 specimens belonging to weight classes 7 (>8 to 16 g) to 9 (>32 to 64 g), which numerically represented 18.5% of the population. Data showed that biomass depended mainly on the presence of large heavy specimens, even though they were always few in number. Moreover, the occurrence of such large thalli at the beginning of summer suggests that Iridaea cordata continues to grow during the long antarctic winter.     

Individual foraging components of harvester ants: movement patterns and seed patch fidelity

Summary We investigated individual foraging components of the western harvester ant,Pogonomyrmex occidentalis, in the native seed background of a shrub-steppe environment. Our study identified factors affecting foraging movements and seed selection by individual ants. Some assumptions and predictions of central-place foraging theory and a correlated random walk were evaluated for individual foragers. Results showed that ant size was only weakly correlated with the seed sizes harvested; seed size was a more important constraint than a predictor of seed selection. Individual ants spent more time in localized search behavior than traveling between search areas and nests.P. occidentalis foragers encountered seeds randomly with respect to time, and handled a mean of 1.7 seeds/trip. A correlation of increased search effort with greater travel distances was consistent with central-place foraging theory but, contrary to it, search and travel effort were not associated with energetic reward.Individual ants exhibited fidelity in both search site and native seed species. Spatial analyses of foraging movements showed a highly oriented travel path while running, and an area-restricted path while searching. Searching ants moved in a manner consistent with a correlated random walk. The deterministic component of patch fidelity and the stochastic component of search may override energetic foraging decisions in individualP. occidentalis ants.     

Influence of root temperature on growth of Pinus sylvestris,Fagus sylvatica,Tilia cordata and Quercus robur

One-year-old tree seedlings were incubated in a greenhouse from April to July, under natural daylight conditions, with their root systems at constant temperatures of 5, 10, 15, 20, 25, 30 and 35 °C and with the above ground parts kept at a constant air temperature of 18–20 °C. The course of height growth, total mass increment, root, shoot and leaf weight as well as leaf areas were measured. The results indicate that clear differences exist in the optimal root zone temperatures for various growth parameters in different tree species. Pinus sylvestris had a maximal height increment at about 5–10 °C and maximal total mass increment at 15 °C root temperature. In contrast, the optimum for Quercus robur was at 25 °C. Tilia cordata and Fagus sylvatica had their optima for most growth parameters at 20 °C. The root temperature apparently indirectly influenced photosynthesis (dry weight accumulation) and respiration loss. From the observed symptoms and indications in the literature it seems probable that a change in hormone levels is involved as the main factor in the described effects. Variation of root temperature had only an insignificant effect on bud burst and the time at which the shoots sprouted. Apparently species of northern origin seem to have lower root temperature optima than those of more southern origin. This is to be verified by investigation of other tree species.     

Calling song and selective phonotaxis in the field crickets,Gryllus firmus andG. pennsylvanicus (Orthoptera: Gryllidae)

The field cricket species, Gryllus firmusand G. pennsylvanicus,occur in a mosaic hybrid zone that roughly parallels the eastern slope of the Appalachian mountains in the northeastern United States. It is important to know what role, if any, the calling song plays in mate choice in sympatric and allopatric populations. In this report, we present results on the variability of calling song properties along transects across this hybrid zone. We also present the results of experiments on phonotactic selectivity of females from an allopatric population of G. firmus.The male calling song of allopatric G. firmuswas significantly slower in temporal rhythm (i. e., chirp and pulse repetition rates) and lower in pitch (i.e., dominant frequency) than that of allopatric G. pennsylvanicus.Calling song properties of males recorded in the hybrid zone varied considerably in temporal and spectral properties. In two-stimulus (choice) phonotaxis experiments, allopatric females of G. firmuspreferred synthetic calling songs with conspecific pulse repetition rates over songs that had lower and higher pulse rates. This preference persisted even when the sound pressure levels of alternative stimuli were unequal. Therefore, allopatric females of G. firmuscan discriminate between conspecific and heterospecific calling songs. Whether or not this same selectivity is present in sympatric populations remains unclear. Investigations of phonotactic selectivity in other allopatric and sympatric populations of both species are currently under way.     

Fruits foraging patterns and seed dispersal effect of frugivorous birds on Hippophae rhamnoides sinensis

Behaviors of 18 species of birds eating fruits of Hippophae rhamnoides spp. sinensis were observed from September 2003 to March 2004. Their foraging patterns were found to be very different and can be divided into five classes: (1) direct swallowing the fruits on crown of the shrubs and sometimes regurgitating seeds soon after; (2) carrying the fruits to their perching sites and swallowing; (3) pecking the fruits from the shrubs to the ground, eating pulp and seeds but leaving pericarp; (4) pecking through the pericarp, eating pulp and leaving pericarp and seeds; (5) pecking through the pericarp on the top of fruits, and only eating seeds. These foraging patterns have different effects on seed dispersal of H. rhamnoides spp. sinensis. The germination experiment of three groups of seeds (seeds from feces, dry fruits and extracted seeds from dry fruits) was carried out. Although ingestion processes of birds had some adverse effects on the seed germination of H. rhamnoides spp. sinensis, the seeds from feces still have a relatively higher germination ratio. H. rhamnoides spp. sinensis provides food to a variety of frugivorous birds, and the birds disperse its seeds. Thus, a mutually beneficial relationship between the bird and the seed is formed. __________ Translated from Chinese Journal of Ecology, 2005, 24(6): 635–638 [译自: 生态学杂志, 2005, 24(6): 635–638]