Historic Anthropogenically Maintained Bear Grass Savannas of the Southeastern Olympic Peninsula

This paper documents the existence and character of a little known fire‐maintained anthropogenic ecosystem in the southeastern Olympic Peninsula of Washington State, U.S.A. Due to cessation of anthropogenic burning, there is no longer an intact example of this ecosystem. We present evidence from Skokomish oral tradition, historical documents, floral composition, tree‐ring analysis, stand structure, and site potential to describe former savanna structure and function. We believe this system was a mosaic of prairies, savannas, and woodlands in a forest matrix maintained through repeated burning to provide culturally important plants and animals. The overstory was dominated by Douglas‐fir (Pseudotsuga menziesii). Bear grass (Xerophyllum tenax) likely was a dominant understory component of the savannas, woodlands, and prairie edges. These lands grew forests in the absence of anthropogenic burning. Wide spacing of older trees or stumps in former stands and rapid invasion by younger trees in the late 1800s and early 1900s suggest a sudden change in stand structure. Shade‐intolerant prairie species are still present where openings have been maintained but not in surrounding forests. Bark charcoal, fire scars, tree establishment patterns, and oral traditions point to use of fire to maintain this system. A common successional trajectory for all these lands leads to forested vegetation. These findings suggest that frequent application of prescribed burning would be necessary to restore this ecosystem.     

Chemosensory control of pollen ingestion in the hoverfly Eristalis tenax by labellar taste hairs

The labellar gustatory system of the dronefly Eristalis tenax L. (Syrphidae; Diptera) that enables the fly to discriminate between pollen and nectar is investigated, and the triggering of pollen ingestion is examined. In behavioural preference tests, exhaustively extracted pollen of the sunflower Helianthus annuus is consumed in smaller amounts than untreated pollen, indicating that water-soluble substances are important for acceptance. Dry pollen is preferred over moist pollen in which the grains stick together, suggesting that mechanical properties of the pollen also play a role in its sensory assessment. Electrophysiological studies of the labellar taste hairs reveal that aqueous extracts of pollen (2% w/v) stimulate the salt receptor cell, but not the sugar receptor cell. The response of the water receptor cell remains the same as to pure water (or standard electrolyte, 10 mmol · l⁻¹ KCl). Of the 20 amino acids tested, the salt cell is sensitive only to proline in a submillimolar range. Behavioural experiments support the electrophysiological findings. When KCl is applied at concentrations eliciting salt-cell spike frequencies equal to those produced by pollen extract (which is often accepted), the water receptor cell is inhibited and a pronounced rejection behaviour occurs. This rejection of concentrated salt solution in Eristalis is therefore mainly mediated by the inhibition of the water cell. Accepted: 27 November 1999     

长尾管蚜蝇Eristalis tenax体色变异的研究

通过对长尾管蚜蝇体色变异的研究,发现该种蚜蝇在体色变异方面有如下特点：（1）腹部色斑的变异形式多样,种群中以浅色者为主,深色的个体比例较少;腹部色斑变异表现出明显的性别差异,雄性变异形式比雌性丰富;（2）后足腿节颜色变异呈现出一定的连续性,从主要呈黑色（肉眼观察）到黄褐色;且这种变化与性别无关;（3）翅上暗色云斑的变化仅有2种形式,种群中具暗色云斑者占大多数;云斑的有无与性别无关;（4）体色变异与发生季节、海拔无关.     

COMPETITION-DEPENDENT ABSCISSION OF SELF-POLLINATED FLOWERS OF PHORMIUM TENAX (AGAVACEAE): A SECOND ACTION OF SELF-INCOMPATIBILITY AT THE WHOLE FLOWER LEVEL?

The relative success of fruit from paired self- and cross-pollinations was examined in Phormium tenax when the contrasted pollinations were separated by different distances on the same and different inflorescences. We determined whether the retention of selfed fruits differed from that of crossed fruits and whether it depended on the level of competition with crossed fruit, the number of seeds per fruit, and/or the presence of earlier developing fruit. We found that the success of selfed fruits is determined by the degree of competition with crossed fruits and may be an expression of self-incompatibility. Competition-dependence of the abscission of selfed flowers has not been documented previously. It is parallel to cryptic self-incompatibility in which individual self-pollen grains are not as successful as cross-pollen when competing on the same pistil. The competition-dependent abscission of self-pollinations considered here, however, operates at the level of whole flowers. The phenomenon of competition-dependent abscission of selfed flowers in P. tenax also has implications for the measurement and interpretation of self-incompatibility in other species. Self-incompatibility is a quantitative phenomenon. The facultative success of selfing shows that the effective strength of self-incompatibility can be highly susceptible to the conditions of competition under which it is measured. The competition-dependent abscission of selfed flowers allows a high level of outcrossing to be achieved while it assures seed set when pollinations are scarce. Several other causes of intermediate selfing frequencies can also be explained by this “best-of-both-worlds” hypothesis.     

Temporal patterns of genetic and phenotypic variation in the epidemiologically important drone fly, Eristalis tenax

Eristalis tenax L. (Diptera: Syrphidae) is commonly known as the drone fly (adult) or rat‐tailed maggot (immature). Both adults and immature stages are identified as potential mechanical vectors of mycobacterial pathogens, and early‐stage maggots cause accidental myiasis. We compared four samples from Mount Fru?ka Gora, Serbia, with the aim of obtaining insights into the temporal variations and sexual dimorphism in the species. This integrative approach was based on allozyme loci, morphometric wing parameters (shape and size) and abdominal colour patterns. Consistent sexual dimorphism was observed, indicating that male specimens had lighter abdomens and smaller and narrower wings than females. The distribution of genetic diversity at polymorphic loci indicated genetic divergence among collection dates. Landmark‐based geometric morphometrics revealed, contrary to the lack of divergence in wing size, significant wing shape variation throughout the year. In addition, temporal changes in the frequencies of the abdominal patterns observed are likely to relate to the biology of the species and ecological factors in the locality. Hence, the present study expands our knowledge of the genetic diversity and phenotypic plasticity of E. tenax. The quantification of such variability represents a step towards the evaluation of the adaptive potential of this species of medical and epidemiological importance.     

Identification and sequence determination of the capsid protein gene of human astrovirus serotype 1

Abstract Pulse labelling experiments and enzyme studies show that Thermoproteus tenax is able to degrade glucose via the Embden-Meyerhof-Parnas (EMP) pathway. T. tenax is the first archeum for which the glycolytic EMP pathway could be established. One of the key enzymes, 6-phosphofructokinase of T. tenax depends on (pyrophosphate-fructose-6-phosphate-1-phosphotransferase) instead of ATP as found in some bacterial and eucaryal species. In addition to the intermediates of the EMP pathway the intermediary products of the non-phosphorylated Entner-Doudoroff pathway were also detected by pulse labelling experiments indicating that under chemoorganotrophic conditions at least 2 glycolytic pathways are operative in T. tenax .     

Phenotypic variation in colour pattern and seasonal plasticity in Eristalis hoverflies (Diptera: Syrphidae)

Abstract.

• 1 An examination of phenotypic variation in colour pattern was carried out on four Eristalis hoverfly species using museum material.
• 2 The amount of phenotypic variation varied substantially among the species with E.arbustorum being the most variable. The other species showed a wide colour pattern range but less variation within that range (E.abusivus and E.nemorum), or a narrow range of colour variation (E.horticola).
• 3 Sexual colour dimorphism was apparent in all four species, but most pronounced in E.abusivus and E.nemorum.
• 4 There were good phenotype-season relationships shown by both sexes in all species, except for female E.abusivus and E.nemorum, with paler insects being more abundant during the warmer summer months.
• 5 Female, but not male, E.arbustorum collected at inland sites were on average paler than those collected at coastal sites. This observation is considered with respect to temperature during the developmental stages.
• 6 The function of colour plasticity in hoverflies is discussed with reference to the need to maintain optimal thermal conditions for activity.

     

Molecular prevalence and zoonotic potential of trichomonads from oral cavities in household dogs

This study investigated the molecular prevalence of oral trichomonads in household dogs. Of the 144 dogs, 21 (14.6%, 21/144) tested positive for oral trichomonads. The prevalence was significantly higher in dogs with severe gingivitis (gingival index 3: 30.0%, 8/26) than that in normal dogs (gingival index 0: 2.7%, 1/37). Therefore, an interaction between oral trichomonads and the development of periodontal disease is suggested. Of the 21 positive samples, 16 isolates were T. brixi, four isolates were T. tenax, and one was Tetratrichomonas sp. Considering T. tenax is recognized as a zoonotic agent, transmission between dogs and humans cannot be neglected.     

Cryptic dioecy and insect pollination in Rosa setigera Michx. (Rosaceae), a rare plant of Carolinian Canada

Rosa setigera is unique among known roses because it is truly dioecious, yet the plants and flowers are almost impossible to sex. Subtle differences in the inflorescences have been detected, for example, there are more flowers per inflorescence on male plants than on female plants and petal expansion from the day of opening to the next day is greater in females than in males; in addition, pollen from female plants appears somewhat collapsed and does not germinate. Pollinators ( Apis mellifera , other bees (Apidae), Eristalis tenax and other Syrphidae: Diptera) visit the blossoms mostly in the morning to collect pollen (there is no nectar) and in choice experiments do not discriminate between male flowers and female flowers on landing, but do spend significantly more time on the former. They do discriminate between freshly opened flowers and day-old flowers, and show marked preference for bouquets of five flowers vs . single flowers. The female plants, with smaller inflorescences and lesser interest to pollen foraging insects, seem to encourage them to forage at more flowers than do their male counterparts. This may be biologically significant for effective pollen flow in a dioecious pollenonly plant with pollenivorous pollinators.     

Floral colours in a world without birds and bees: the plants of Macquarie Island

We studied biotically pollinated angiosperms on Macquarie Island, a remote site in the Southern Ocean with a predominately or exclusively dipteran pollinator fauna, in an effort to understand how flower colour affects community assembly. We compared a distinctive group of cream‐green Macquarie Island flowers to the flora of likely source pools of immigrants and to a continental flora from a high latitude in the northern hemisphere. We used both dipteran and hymenopteran colour models and phylogenetically informed analyses to explore the chromatic component of community assembly. The species with cream‐green flowers are very restricted in colour space models of both fly vision and bee vision and represent a distinct group that plays a very minor role in other communities. It is unlikely that such a community could form through random immigration from continental source pools. Our findings suggest that fly pollination has imposed a strong ecological filter on Macquarie Island, favouring floral colours that are rare in continental floras. This is one of the strongest demonstrations that plant–pollinator interactions play an important role in plant community assembly. Future work exploring colour choices by dipteran flower visitors would be valuable.