Plants and insects in early old-field succession: comparison of an English site and an American site

The plant and insect communities of early, secondary succession beginning with bare ground in an Old World site (southern Britain) and a New World site (Iowa, U.S.A.) shared a number of characteristics. Both sites showed similar temporal patterns of plant species cover and species richness, although overall richness was greater at the Old World site. Annuals dominated at both sites during the first year of succession and were largely replaced by perennials in the second year. Monocotyledons were more abundant at the Old World site, especially in the second year. The two sites differed markedly in the contribution of native and introduced plant species, with the Old World site dominated by natives and the New World site by alien plant species. Insect herbivore load was greater at the Old World site, when expressed in terms of structural complexity of the vegetation, suggesting that there may be major differences in the influence of herbivores on the direction and rate of succession at the two sites.     

Development of the magnetic capture system for recovery of Xiphinema americanum

Xiphinema americanum is listed as a quarantine nematode by The European Plant Protection Organisation because of its ability to transmit quarantine viruses. Detection of this nematode in soil samples, or in mixed nematode samples extracted from soil, is therefore of paramount importance. We recently described the use of magnetic beads (Dynabeads) in combination with probes such as lectins or antibodies for recovery of small endoparasitic nematodes including Meloidogyne spp. and Globodera rostochiensis from mixed nematode samples. Here we show that magnetic capture can be used with much larger nematodes such as X. americanum. We describe lectins and antisera that bind to the surface of this nematode and show that the antisera can be used in the Dynabeads system to recover and enrich X. americanum from mixed nematode samples.     

Faecal case architecture in the gibbosus species group of Neochlamisus Karren, 1972 (Coleoptera: Chrysomelidae: Cryptocephalinae: Chlamisini)

Constructions composed of faeces are rare in insects, but occur in certain leaf-beetle clades. Members of the subfamily Cryptocephalinae share a complex behavioural and morphological synapomorphy, involving portable faecal cases that house the immature stages. A maternally initiated egg case is expanded and enlarged through four larval stadia, then sealed to provide a pupal chamber from which adults eventually emerge. We analyse and compare faecal-case architecture in ten taxa of the cryptocephaline genus Neochlamisus , and assess structural variation within a life cycle, between different 'host forms' of Neochlamisus bebbianae , and among species. These cases proved to be comprised primarily of faeces, with plant trichomes representing the only common secondary component. General architectural trends reflected variation in shape, faecal texture, and the incorporation and density of trichomes. Deviations of the Neochlamisus case from a simple geometrical gnomon reflect the changing body size of the animal, differential application of faeces, and shifts in the orientation of the carriage of the case. Neochlamisus cases are presumably energetically costly to produce, carry, and maintain, and some adaptive hypotheses of case evolution are proposed. Additionally, literature on case morphology in other camptosomates is reviewed.  © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society , 2008, 152 , 315–351.     

Mechanism of iron uptake by plants

Abstract. Green plants require a continuous supply of Fe as they grow, because Fe does not not move from the older to the newer leaves. Soils do not lack Fe per se , but it may not be available to plants grown in alkaline soils. Plants are classed 'Fe-efficient' if they respond to Fe-deficiency stress by inducing biochemical reactions that make Fe available in a useful form, and 'Fe-inefficienT' if they do not. Iron uptake induced in response to Fe stress involves release of hydrogen ions and reductants by the root. The lowered pH and presence of reductant at the root zone, along with reduction of Fe³⁺ to Fe²⁺ at the root surface, enables Fe²⁺ to be taken up primarily through the young lateral roots. Ferrous iron is present throughout the protozylem and may or may not have entered the root by a carrier. The root-absorbed Fe²⁺ is oxidized to Fe³⁺ at the junction of the protoxylem and the metaxylem, chelated by citrate, and then transported in the metaxylem to the plant top. In the plant, the chemical reactions injuced by Fe-deficiency stress may affect nitrate reductase activity, use of Fe from Fe³⁺ phosphate and chelating agents, and tolerance to heavy metals. An efficient mechanism for Fe uptake in roots appears to be important for the efficient use of Fe in plant tops.     

Geographical patterns of evolution in Neotropical Lepidoptera: differentiation of the species of Melinaea and Mechanitis (Nymphalidae,Ithomiinae)*

Abstract Biosystematic analysis incorporating abundant new field data from many parts of the Neotropics has led to an ordered revision of the mimetic ithomiine genera Melinaea and Mechanitis. The various polytypic species of these general probably served as prime movers for the differentiation of other mimetic butterflies in Quaternary forest refuges. The revisions are presented in the form of supplements to the works of Richard M. Fox on these genera, with analyses based on his divisions. Seven species (or monophyletic species-groups) and sixty-three well-differentiated geographic subspecies (six of these described here for the first time) are recognized in Melinaea. Specimens are illustrated which demonstrate intergradation between refuge-derived subspecies. Five species and fifty-two differentiated subspecies are recognized in Mechanitis, whose members are more abundant and gregarious, more plastic, and apparently more vagile than those of Melinaea, resulting in fewer clear-cut mimetic associations, more extensive blurring of differentiation patterns, and apparently fewer incipient biological species in this genus than in Melinaea.