Abundance–body mass relationships among insects along a latitudinal gradient

Abstract We investigated the relationship between abundance and body size (body mass) of 162 insect herbivore species on the host plant Acacia falcata along its entire coastal latitudinal distribution (eastern Australia), spanning a gradient in mean annual temperature of 4.3°C. We extend previous research by assessing these relationships at different spatial scales (latitudes pooled, among latitudes and within latitudes) and at different taxonomic levels (insect phytophages pooled, phytophagous Coleoptera and Hemiptera, and five component suborders/superfamilies). Insect species were collected from two orders (Hemiptera and Coleoptera) and five component suborders/superfamilies. There were no consistent trends in the relationships (linear or polygonal/hump‐shaped) between abundance and body mass when latitudes were pooled, among latitudes, or when phytophagous insect species were separated into their component suborder/superfamily groups. The reason for the lack of consistent trends might be due to the insect herbivores not fully exploiting their host plant and the relative absence of competition among herbivore species for food resources. This is further assessed in relation to the lack of a consistent pattern in species richness of Coleoptera and Hemiptera herbivores from the same dataset and rates of chewing and sap‐sucking herbivory along the same latitudinal gradient. Future studies of abundance–body size relationships are discussed in relation to sampling across environmental gradients and accounting for the influence of host plant identity and insect phylogeny.     

In vivo algal fluorescence, spectral change due to light intensity changes and the automatic characterization of algae

SUMMARY. 1 Total fluorescence spectra of thirty-two freshwater algae show that the majority of the information is contained in the excitation spectrum of emission at 680 nm.
2. Previously suggested characteristics for the automatic identification of blue-green algae from their fluorescence properties, i.e. the presence of high phycoerythrin fluorescence and low chlorophyll fluorescence, are shown to be inapplicable to the freshwater blue-green algae studied here.     

Long-term and seasonal changes in the chemical composition of precipitation and surface waters of lakes and tarns in the English Lake District

SUMMARY. The composition of bulk (wet and dry) precipitation in 1975 and 1976 was similar to that found 22 years previously. In 1975, mean values for nine precipitation samplers at one site (Wraymires) ranged from pH 4.3 to 4.5; similar values were obtained in 1976. Samplers covered with fine-mesh plastic gauze caught substantially more Ca²⁺ and K⁺ than open samplers, but pH and SO^2-₄+ NO₃^- concentrations were similar in open and covered samplers. In precipitation, c. 50% of H⁺ was balanced by NO₃^- and c. 50% by SOi; 80% of the SO^2-₄ was balanced by Ca²⁺ and Mg²⁺. Conccntrations of major cations (H⁺, Na⁺, K⁺,Ca²⁺, Mg²⁺) and anions (CI^-, NO₃^- SO^2-₄ and alkalinity [Alk—largely HCO₃^-]) in upland water- bodies were similar to those found in precipitation, but pH levels were generally higher and above 6.0 m some tarns. At lower altitudes, on base-rich roeks and soils, Ca²⁺ and Alk become dominant. Results of a survey of lakes and tarns in 1974–78 are compared with a survey in 1953–56 and published data (chiefly for pH and Alk) for 1947–50, 1932 and 1928. Comparisons are also made with other measurements of Alk in three productive lakes (Blelham Tarn, Esthwaite Water and Windermere) for 1936–39 and 1945–80. Winter levels of NO₃-N, PO₄-P and Si are given for these lakes; although the first two have increased during the late 1960s and the 1970s there has been no significant change in the last. NO₃^- and probably some SO^2-₄. In productive lakes a substantial (c. 50%) rise in mean Alk occurred during the late 1960s and the 1970s, possibly related to increased winter levels of NO₃-N and PO₄-P derived from sewage and fertilizers. In this period the maximum pH levels reached in summer were notably high, sometimes exceeding pH 10. The rise in Alk, conductivity and pH of surface waters is influenced by climatic factors (a decade of drier years), sewage input and biological productivity within the lakes. Considerable seasonal fluctuations in the concentrations of major ions, a characteristic feature of surface waters in the English Lake District, are illustrated and some implications for cation-anion balance briefly discussed. Mid-winter concentrations are usually high forNa⁺, K⁺, Cl^-. NO₃^-and low for Ca²⁺, Mg²⁺, Alk. SO^2-₄. Alkalinity. pH and conductivity of Lake District tarns and lakes show no signs of acidification during the period 1928–80. On the contrary, productive lakes have become more alkaline and some unproductive low-alkalinity (< 100 μ-equiv. 1^-1) lakes also show signs of alkalization, with increased mean concentrations of Na⁺. Ca²⁺ and Mg²⁺, balanced by Alk.     

Antigenic analysis of potato virus A particles and coat protein

Five monoclonal antibodies (MAbs) were prepared to particles of potato virus A (PVA), isolate B11. In immunoblots, MAbs A1D8 and A5B6 reacted only with full length molecules of PVA coat protein (CP). Pepscan tests with overlapping octapeptides representing the whole sequence of PVA CP showed that the epitope detected by MAb A5B6 is contained in its N-terminal octapeptide. MAbs A9A4, A3H4 and A6B8 reacted with CP molecules that lacked about 5 kD of sequence at their end(s) and detected epitopes at residues 52 to 62, 64 to 73 and 75 to 82 respectively, all of which lie in the protease-resistant core of the CP. The epitope which reacts with MAb A3H4 is in a region predicted to be hydrophobic and is not detected in intact virus particles, indicating it is a cryptotope. In contrast, MAbs A6B8 and A9A4 reacted with freshly purified PVA particles but more strongly with partially degraded ones. Pepscan tests with polyclonal antibodies to PVA isolate B11 identified five additional immunogenic sequences in PVA CP and showed that regions at the N-termini of the intact and core molecules are immunodominant. PVA isolate B11 was not transmitted by aphids, and its CP N-terminal octapeptide contains the sequence DAS, which is associated with aphid-non-transmissibility in other potyviruses. MAb A5B6, which detects this region, reacted strongly in ELISA with three out of four other aphid-non-transmissible PVA isolates but only weakly with three aphid-transmissible ones, suggesting that differences in N-terminal sequence may underlie most of the differences in aphid transmissibility.     

Properties of cocksfoot streak and cocksfoot cryptic, two viruses infecting cocksfoot (Dactylis glomerate) in Scotland

A Scottish isolate of cocksfoot streak virus (CSV-S) was found to have flexuous filamentous particles which, in sap of infected cocksfoot plants, had a modal length of 712 nm. It was transmitted from infected to healthy cocksfoot plants in a non-persistent manner by Myzus persicae and by mechanical inoculation of infective sap extracts containing an anti-oxidant. Apart from cocksfoot, mechanical inoculation of infective sap succeeded in infecting only four of 22 plant species tested. The infectivity of sap extracts containing 0.2% thioglycerol was lost after heating for 10 min at 55^oC but not 50^oC, storage at room temperature for 48 but not 24 hours, and after diluting 10-2 to 10-3. Highly purified preparations of CSV-S particles sedimented as a single component with a sedimentation coefficient of 139S and had a buoyant density in rubidium bromide of 1.31 g/cm3. Virus particles were composed of one protein and one ssRNA species with estimated Mr of 31 000 and 3.2 times 106 respectively. In ELISA, an antiserum prepared to CSV-S detected the virus in all aerial parts of infected cocksfoot plants and, when present in the ratio of 1 infected leaf: 1000 healthy leaves. Both CSV-S-infected and -uninfected cocksfoot also contained a previously undescribed virus with isometric particles c. 30 nm in diameter. This virus, named cocksfoot cryptic virus (CCV), was seed-borne in two cvs of cocksfoot tested and its particles contained two dsRNA species of estimated Mt of 1.14 times 106 and 1.27 times 106. Despite the fact that particles of CSV-S were largely free from CCV particles following exclusion chromatography on agarose beads prior to immunisation, immunoelectron microscopy (IEM) showed that the antiserum prepared to CSV-S also contained some antibodies to CCV. Evidence from IEM suggested a possible distant serological relationship of CCV to ryegrass and beet (BCV 1 or BCV 2, or both) cryptoviruses, all members of sub-group A of cryptoviruses.     

Effects of zebra mussel attachment on the foraging behaviour of a larval dragonfly,Macromia illinoiensis

1. Larvae of Macromia illinoiensis Walsh are often colonised by the zebra mussel, Dreissena polymorpha Pallas, a recent invader to North America. To determine how mussel attachment affects an individual's foraging behaviour, we quantified capture of Hexagenia limbata Hexes mayfly prey and the distance moved by newly‐molted final instars before and after an individual's colonisation with zebra mussels. 2. In night trials, larvae sprawled above the sand, and caught more mayflies than individuals in daytime trials, but the estimated distance travelled did not differ. When resting under a layer of sand with only its eyes exposed during the day, an individual could capture a mayfly prey using a sit‐and‐wait ambush strategy. When sprawled above the sand, some larvae caught prey that rested on their legs. 3. When mussel‐free, individuals captured more prey than they did when carrying zebra mussels, although mussel attachment per se did not affect the estimated distance that a larva moved. 4. During day trials, but not night ones, the increasing mussel load of colonised individuals decreased prey capture and the distance moved in an apparent step‐wise function. Although the number of mussels carried did not differ, night foragers carried a heavier load. Independent of time of the day, the distance an individual travelled when mussel‐free was predictive of the number of prey it caught when colonised, suggesting that the greater general activity of some individuals helped mitigate negative effects that mussel attachment had on prey capture. 5. Our results add to a growing number of negative effects of zebra mussel colonisation on sprawling and hiding dragonfly larvae. Although the impact of these costs on dragonfly populations remains to be determined, a decrease in this guild of predators whose life cycle spans aquatic and terrestrial habitats might have cascading effects across ecosystems.     

Life-history patterns in British Umbelliferae: a review

British Umbelliferae form a natural cohesive taxon, having patterns of habitat distribution, reproductive biology and life-history that distinguish them from other British dicotyledons. They are usually found in open sites, and are local or rare in distribution.
Almost half of British species have the andromonoecious sex habit. Perfect flowers are usually protandrous. The floral composition of umbels, and the pattern of opening of the inflorescence combine to produce a protogynous effect. These have been interpreted as mechanisms which decrease competition for resources between male and female functions in the plant, such that separate maternal and paternal fitness can become optimal.
Seeds often require a chilling treatment, alternating temperatures, or a period of after-ripening before they are capable of germination. Schizocarps are of low weight. This seems to relate to the relative openness of habitat wherein unbellifers are found. Patterns of dry matter distribution reflect the life-history strategies of various umbellifer species. Agromyzid leaf miners parasitize the more widespread species, and those which arc found in a greater number of different habitats.     

The environmental significance of Lingula in the Ludlow Series of the Welsh Borderland and Wales

Cherns. Lesley 1979 01 15: The environmental significance of Lingula in the Ludlow Series of the Welsh Borderland and Wales. Lethaia . Vol. 12. pp. 35–46, Oslo. ISSN 0024–1164.
The inarticulate brachiopod Lingula is commonly regarded as an indicator of very nearshore environments, particularly when found in monospecific assemblages. However, neither of the two common species in the Lower Leintwardine Beds, L. lewisii and L. lata . which occur commonly in such associations, have distributions indicative of such an environment. Their Occurrence correlates closely with the Leintwardinian palaeogeography. The former species is concentrated in shelf areas, the latter is confined to the basin; the two distributions overlap little. Individuals of both species are found articulated and perpendicular to the bedding, apparently in situ . Hence, the species may be inferred to have equivalent, infaunal modes of life comparable to living representatives of the family. The basinal distribution of L. lara is an original feature. The depth of the actively subsiding basin was relatively great, judging from sedimentological and palaeogeographical evidence. Therefore, L. lata was a species adapted to 'deep-water' environments. The lingulid distributions, reviewed against the concept of brachiopod depth-related communities previously defined for the Ludlow show the latter to be inapplicable in the Leintwardinian. The depth significance postulated for the recurrent species associations typical of the shelf sequences cannot be accepted.