The separation of Liriomyza huidobrensis (Diptera: Agromyzidae) from related indigenous and non-indigenous species encountered in the United Kingdom using cellulose acetate electrophoresis

The non-indigenous pest leaf miner Liriomyza huidobrensis and its close relatives L. bryoniae and L. strigata belong to a natural group. These species can be separated from one another by means of protein electrophoresis on a cellulose acetate membrane. The protocol for this diagnostic assay involves staining for two enzymes, glucose-6-phosphate dehydrogenase (G6PDH) and leucine-glycine peptidase (PEP). Other leaf miner species that might also be found under glass, Chromatomyia syngenesiae, C. horticola and the non-indigenous L. trifolii and L. sativae , are clearly distinguishable from the L. huidobrensis group of species by this assay. The effect of parasitism on L. huidobrensis by Dacnusa sibirica was investigated and shown unlikely to cause misidentification of the leaf miner host. Results obtained from practical use of the assay to identify unknown specimens from ports and nurseries are compared with those obtained from flies kept in laboratory culture and used during development of the assay. No new variation was found for G6PDH. New PEP variation was found for both L. huidobrensis and L. bryoniae but this did not affect the integrity of the assay. A biochemical key to these agromyzid leaf miners is presented.     

Nectar utilization and pollination by Australian honeyeaters and insects visiting Calothamnus quadrifidus (Myrtaceae)

Nectar availability in Calothamnus quadrifidus flowers was studied at Wongamine Nature Reserve in late spring (November). Despite some overnight depletion by moths and other invertebrates, more nectar was present in flowers at dawn than at the preceding dusk. Significant nectar depletion occurred within a few hours after dawn, mainly due to foraging by two honeyeater species. Lichmera indistincta and Phylidonyris nigra. Thereafter, nectar availability was maintained at relatively low levels, principally because of foraging by honeyeaters and honey bees. Apis mellifera, that became active during the warmer part of the day. Although individual honeyeaters consumed more nectar than A. mellifera, honey bees were so abundant that their total impact was greater than that of either honeyeater species for much of the day. Transfer of C. quadrifidus pollen between flowers is necessary in order to achieve a high level of seed set, as the flowers appear to be protandrous. Honeyeaters appeared to be considerably more significant pollen vectors than A. mellifera.     

Survivorship of the sexual and agamic generations of Andricus quercuscalicis on Quercus cerris and Q.robur

ABSTRACT.

• 1 Survivorship within the galls of the sexual and agamic generations of Andricus quercuscalicis (Burgsdorf) is estimated from field populations.
• 2 The sexual generation on Turkey oak suffers a 20% death rate through parasitism by Mesopolobus spp. The emerging parasitoids are virtually all males.
• 3 The agamic generation on the acorn cups of English oak is not attacked by any parasites or inquilines at our Berkshire site despite the fact that most of the species which parasitize the gall in continental Europe are on the British list.
• 4 Agamic galls cause average losses of between 30% and 50% of the total acorn crop in different years. Individual trees differ greatly in their rates of loss, many losing over 90%, others losing virtually none.

     

Effects of Ionizing Radiation on Bacterial DNA-membrane Complexes

THE model proposed by Alper¹ for lethal radiation damage to cells is based on inferential evidence that there are two important sites of damage by ionizing radiation. At one site, damage referred to as type “N” is associated with a low oxygen enhancement ratio (OER) and is probably to nucleic acid, while at the other site, type “O” damage is associated with a considerably higher oxygen enhancement value and is to a non-nucleic acid target. The model demands that the two values of OER are respectively less and greater than that observed for the overall lethal effect. More recently² Alper reviewed further inferential evidence³ that cell membranes are the site of type O damage, though there may be subsequent interaction with the lesions following energy deposition in DNA⁴.     

Reproductive biology of the rare and endangered Banksia brownii Baxter ex R. Br. (Proteaceae)

Abstract Banksia brownii is an endangered species, now limited to ～ 15 disjunct populations in southwestern Western Australia. Data on flowering phenology, plant size, fruit set, pollination and the mating system were gathered for two of these populations between March and October 1993. Flowering for both populations followed a similar pattern, with open flowers first evident in April, and the number of inflorescences with open flowers peaking in June. At both locations, trees differed considerably with respect to their size, the total number of inflorescences produced and the length of their flowering season. Fruiting success was typically low, with approximately half of all inflorescences failing to develop into infructescences. Only 1. 8% of the flowers originally present on inflorescences developed into follicles. The distribution of follicles along each infructescence was non-random, with most forming in the middle third of the infructescence for reasons relating to nutrient supply and pollinator behaviour. More flowers opened during the day than at night, although pollen was lost from individual flowers during both periods. Honeyeaters such as Phylidonyris novaehollandiae were common at the two study sites, and often carried large loads of B. brownii pollen. Though less frequently caught, the nocturnal mammals Rattus fuscipes and Tarsipes rostratus also bore substantial amounts of pollen. Most inflorescences from which these mammals and birds were excluded remained barren. Fruiting success was further reduced when invertebrates such as Apis mellifera were also prevented from visiting inflorescences. The ability of B. brownii to set at least some fruit in the absence of biotic poli-nators indicates that the species is partially self-compatible. Honeyeaters foraged preferentially at inflorescences with one to two thirds of their flowers open, probing mainly along the ‘advancing front’ of open flowers. These animals moved more frequently between inflorescences on the same plant than between those on different plants, and were often recaptured in the same locations. Mammals also appeared to be sedentary. Both B. brownii populations had mixed mating systems, with genetically determined outcrossing rates of ～0.7. The unusually high level of selfing in each population is presumably a reflection of the species’ self-compatibility and the foraging behaviour of its pollinators.     

Solute Regulation in the Euryhaline Marine Alga Enteromorpha prolifera (O. F. Mull) J. Ag.

Young, A. J., Collins, J. C. and Russell, G. 1987. Solute regulationin the euryhaline marine alga Enteromorpha prolifera (O. F.Mll) J. Ag.—J. exp. Bot. 38: 1298–1308. The physiological basis for salt tolerance has been studiedin the euryhaline alga Enteromorpha prolifera. Levels of inorganicions and organic (compatible) solutes have been measured. K⁺makes the major contribution towards the internal osmotic potentialof the cell, while Cl^– and, in particular, Na⁺ contentsare low. Levels of the organic solute ß-dimethylsulphonio-propionate(DMSP) are high but are fairly insensitive to changes in theexternal salinity. Levels of amino-acids, calcium, phosphateand sulphate contribute relatively little towards the internalosmotic potential of the alga. As salinity is altered there are marked changes in the tissuewater content and volume. These changes directly affect theconcentration of the osmotic solutes within the cell. In diluteseawaters there is an increase in turgor as there is littlechange in the internal solute content of the cell compared tovalues in normal sea water. Inorganic ions, in particular K⁺,and organic solutes are accumulated in concentrated seawaters,although concentrations greater than 2·00 x seawaterresult in a reduction in the internal osmotic potential of thecell, mainly through loss of K⁺. Key words: Enteromorpha, salinity, osmoregulation     

Ecotypic Variation in the Osmotic Responses of Enteromorpha intestinalis (L.) Link.

Young, A. J., Collins, J. C. and Russell, G. 1987. Ecotypicvariation in the osmotic responses of Enteromorpha intestinalis(L.) Link.—J. exp. Bot. 38: 1309–1324. The physiological basis for salt tolerance has been studiedin the euryhaline marine alga Enteromorpha intestinalis. Adaptationto dilute and concentrated seawaters has been investigated inthree separate populations of this alga: marine, rock pool andestuarine. Internal K⁺, Na⁺ and Cl^– levels have been determined usingtracer efflux analyses. K⁺ has been shown to be the major osmoticsolute within this alga. Cellular levels of Cl^– and, inparticular, Na⁺ are low although levels in the cell wall arehigh. Levels of these ions varied considerably between the separateplants; K⁺ levels within marine plants of E. intestinalis aretwo to four times those found in the other populations. Thetertiary sulphonium compound ß-dimethylsulphonio-propionateis maintained at relatively high levels, although it remainsfairly insensitive to change in the external salinity. Changes in the tissue water content and cell volume are large,particularly within the estuarine plants. The thin cell wallsof these plants allow large changes in volume in the diluteconditions experienced in an estuary, while low turgor preventscell rupture. Thicker cell walls and small cells of the marineand rock pool plants assist in tolerating high and low externalosmotic potential—the estuarine plants respond poorlyto concentrated seawater. Key words: Enteromorpha, osmoregulation, ecotypes     

The Effects of Temperature on Leaf Growth in Cyperus longus, a Temperate C4 Species

Plants of the C₄ sedge Cyperus longus L. were grown at 10, 20and 30 °C. An asymptotic growth curve, the Richards function,was fitted to growth data for successive leaves. The mean rateof leaf appearance was a linear function of temperature with0.014 leaves appearing per day for every 1 °C increase intemperature. The instantaneous relative rate of leaf extensionshowed a marked ontogenetic drift which was most rapid at 30°C and slowest at 10 °C. The mean absolute extensionrate for foliage had a temperature coefficient of 0.16 cm d^–1° C^–1 in the range from 10 to 30 °C. The durationof leaf growth was independent of leaf number at 10 and 20 °Cbut increased linearly with leaf number at 30 °C. The smalldifferences in relative growth rate at the three temperaturesresulted in large differences in foliage area produced at theend of a 30 d growth period. The final foliage areas at 20 and10 °C were 51 and 9% respectively of that at 30 °C. Cyperus longus, temperature, leaf growth, Richards function, growth analysis     

A comparative study of epiphytic algal communities on two common genera of sea-grasses in eastern Australia

Fifty-seven epiphytic species were found to occur on the two sea-grass hosts Zostera and Posidonia in Botany Bay and Jervis Bay, N.S.W. Among the algal epiphytes on Posidonia australis several indicator species were identified and it was found that their relative frequency of occurrence can be used to differentiate sites within the two bays. These indicator species can be used also to classify a collection from an unknown site within the region, and their relative occurrences may provide a useful index for early detection of changes in the bay environments.