Landscape ecology of the burrowing bettong: Warren distribution and patch dynamics in semiarid eastern Australia

Abstract In arid and semiarid Australia fossorial vertebrates have been a major component of the soil biota mediating many fundamental landscape processes. However, many species such as the burrowing bettong (Bettongia lesueur) have become seriously depleted following European pastoral settlement. As ‘landscape engineers’, they were responsible for creating and maintaining a high degree of surface heterogeneity that promoted a diverse and productive herbaceous understorey, particularly in ‘hard‐red’ communities dominated by mulga (Acacia aneura). While their regional extinction has had major impacts by contributing to desertification and loss of biodiversity, relict warrens ‘engineered’ by B. lesueur still remain in certain ecosystems and despite continual weathering, contribute significantly to herbage productivity and species diversity. This paper details the results obtained from a number of field studies aimed at determining the distribution of relict warrens at contrasting scales and their influence on landscape patch dynamics resulting from their impacts on soil nutrients, herbage composition and herbivory. Finally, the conservation implications following the continental extinction of this species and the resulting loss of fundamental ecosystem services, as well as cultural values, are discussed in the context of future re‐introduction efforts.     

Phototropism and geotropism in hypocotyls of cress (Lepidium sativum L.)

Abstract. The phototropic and the geotropic sensitivities of cress hypocotyls differed in etiolated and in green seedlings. In etiolated seedlings, phototropism was poorly developed and geotropism seemed to be the dominant orientation mechanism. In green seedlings, although geotropic sensitivity was slightly greater, phototropic responses were markedly enhanced, such that photo-signals could over-ride, or even reverse, geocurvature. The 'de-etiolation' light pretreatments required to bring about these changes in the photo-and geo-systems were different. The slight enhancement of geocurvature could be achieved by short-term exposure to red light and was reversed by far-red irradiation. The marked stimulation of photocurvature required extensive irradiation pretreatments.     

Breeding biology and incremental benefits of outcrossing for the restoration wildflower,Hedysarum boreale Nutt. (Fabaceae)

Northern sweetvetch (Hedysarum boreale Nutt.) is an herbaceous perennial legume of the Rocky Mountains, USA, whose seed is desired for rehabilitating degraded plant communities. Through experimental pollinations, the necessity of pollinators was shown by the failure of autogamy, despite stigmas first becoming receptive in the bud in close proximity to the dehiscing anthers. Nonetheless, the species proved to be self‐fertile, initiating as many fruits through selfing as outcrossing. Incremental benefits of outcrossing only later manifested in superior fruit development, seed maturation and seed germination. Farming of H. boreale can yield abundant viable seed if adequately visited by pollinating bees.     

Non-clonal evolution of microbes

Horizontal gene transfer is the collective name for processes that permit the exchange of DNA among organisms of different species. Only recently has it been recognized as a significant contribution to interorganismal gene exchange. Traditionally, it was thought that microorganisms evolved clonally, passing genes from mother to daughter cells with little or no exchange of DNA among diverse species. Studies of microbial genomes have shown, however, that genomes contain genes that are closely related to a number of different prokaryotes, sometimes to phylogenetically very distantly related ones. Whereas prokaryotic and eukaryotic evolution was once reconstructed from a single 16S ribosomal RNA (rRNA) gene, the analysis of complete genomes is beginning to yield a different picture of microbial evolution, one that is wrought with the horizontal movement of genes across vast phylogenetic distances. © 2003 The Linnean Society of London. Biological Journal of the Linnean Society , 2003, 79 , 27–32.     

Effects of maternal diet on offspring fitness in the bird cherry‐oat aphid

1. Maternal and offspring diet effects on life‐history traits of the bird cherry‐oat aphid Rhopalosiphum padi were tested on three wheat varieties. Using nine reciprocal combinations of wheat varieties, the effects of previous experience (maternal diet effect) on the aphid's response to resistant and susceptible varieties (offspring diet effect) were tested. Batis was susceptible, and Xiaoyan22 and Ww2730 were both resistant, but with different mechanisms. 2. Aphids produced the most alatae in the treatments with the most resistant maternal diet variety Xiaoyan22. The fecundity (F) and intrinsic rate of increase (r_m) of these alatae were at their greatest in the most resistant offspring diet variety, but these traits were not influenced in the apterae. 3. There were significant interactions in the alatae production and apterae life‐history traits, such as r_m, development time, weight gain, and mean relative growth rate, between the maternal and offspring diet varieties. The interactions in apterae responses between varieties, some of which were reciprocal, indicated phenotypic plasticity in these parthenogenetic aphids. 4. Rhopalosiphum padi produced more alatae on the most resistant variety; the alatae would disperse and were more fecund. The growth responses of the apterae showed phenotypic plasticity to the different combinations of maternal and offspring diet varieties. The phenotypic plasticity would allow R. padi to better utilise the variable environments represented by the small wheat plots of different varieties in China.     

Flow velocity underpins microhabitat selection by gobies of the Australian Wet Tropics

1. Water flow is a critical driver of aquatic ecosystem health and function. Amid rising concerns over changing flow regimes, there is an urgent need to understand the functional mechanisms by which flow influences patterns of freshwater biodiversity. 2. We explored the functional link between flow velocity and microhabitat specialisation in a speciose group of freshwater gobies (comprising over half the total fish species richness) within insular streams of the Australian Wet Tropics under base flow conditions. We addressed two particular questions: (i) What is the relative selectivity of species towards streambed composition and water flow velocity? and (ii) Can patterns of microhabitat occupation be explained by differences in intrinsic flow performance among species? To answer these questions, we combined visual field observations of microhabitat use with flow tank assessments of flow speed performance. 3. Tropical freshwater gobies displayed strong specificity towards flow velocities, while being relatively non‐selective towards streambed composition. At opposite extremes of the spectrum, we found Sicyopterus lagocephalus occupying high‐flow (>1.0 ms^?1) microhabitats while Redigobius bikolanus selected slower‐flow (<0.05 ms^?1) areas. These patterns of microhabitat flow specificity were largely explained by the different abilities of species to swim and/or cling to the substratum under these different flow settings. 4. Our findings confirm suggestions that predictable base flows in tropical streams support habitat specialists, which include one species capable of occupying areas of extremely high flow that very few other fishes can withstand. 5. The functional link between flow and gobioid fish distribution patterns could occur throughout tropical streams of the Indo‐Pacific and Caribbean as a widespread phenomenon that may help inform stream flow management guidelines to maintain this substantial component of tropical freshwater biodiversity around the globe.     

Genetic engineering of malaria parasite resistance in vector mosquitoes

Malaria is the most significant vector‐borne disease and mostly affects people living in the lesser developed countries of tropical and sub‐tropical regions. Climate changes, rapid global transportation, immigration and invasion of exotic mosquito vectors bring the threat of introduction of the disease to developed nations. Sustainability of malaria control requires the discovery of therapeutic and prophylactic drugs, development of effective vaccines and control of vector mosquitoes. Drug development and vaccine research have been pursued aggressively over the past 20 years, and progress in novel approaches to vector control is now evident. Our long‐term objective is the production and utilization of strains of vector mosquitoes that are genetically refractory to the transmission of malaria parasites. These insects will be used to test the hypothesis that an increase in the frequency of a gene or allele that confers decreased vector competence to a population of mosquitoes will result in a reduction in the incidence and prevalence of malaria. Completed studies make it possible to develop strains of Anopheles mosquitoes expressing specific effector molecules that interfere completely with the transmission of the most lethal human malaria parasite, Plasmodium falciparum. Data are reviewed here that support the use of single‐chain monoclonal antibodies (scFv) that disable parasites in the midgut and hemolymph of transgenic mosquitoes.