The diversity of ant–plant interactions in the rainforest understorey tree, Ryparosa (Achariaceae): food bodies, domatia, prostomata, and hemipteran trophobionts

Ant–plant relationships, with variability in both intimacy and the trophic structure of associations, are described for the Austro-Malesian rainforest tree genus Ryparosa (Achariaceae). The range of associations involves opportunistic interactions between plants and foraging ants, mediated by food bodies, and tighter associations in which ant colonies, tending hemipteran trophobionts, reside permanently in plant structures with different degrees of adaptation to house ants. Our study provides strong baseline data to suggest that Ryparosa could become a new model system for examining the evolutionary radiation of ant-related traits. To define the diversity of ant–plant associations in Ryparosa , we first present a review of ant-plant terminology and an outline of its use in this study. Field studies of ant interactions with food bodies in myrmecotrophic R. kurrangii from Australia and the association between myrmecoxenic R. fasciculata and two Cladomyrma plant-ant species on the Malay Peninsula provide detailed examples of ant–plant interactions. An examination of herbarium material revealed a diverse range of ant–plant associations in other Ryparosa taxa. All 27 species had evidence of food body production, seven species had evidence of stem inhabitation by ants, five species had specialized stem domatia, and the domatia of R. amplifolia featured prostomata. Variation in the specificity of Ryparosa ant–plant interactions is discussed in relation to known ant partners and other ant–plant associations.  © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 154 , 353–371.     

Effects of Roads on Endangered San Joaquin Kit Foxes

ABSTRACT San Joaquin kit foxes (Vulpes macrotis mutica) occur in central California, USA, and are endangered due to habitat loss and degradation. As the human population of California grows, more roads are being constructed in remaining kit fox habitat. We examined effects of 2-lane roads on demographic and ecological patterns of kit foxes on the Lokern Natural Area (LNA) from August 2001 to June 2004. Of 60 radiocollared kit foxes, only one was struck by a vehicle. Foxes were assigned to 1 of 3 risk categories (high, medium, or low) based on proportion of time spent in road-effect zones, which were defined by the probability of a fox encountering a road during nocturnal movements. Fox survival probabilities, reproductive success, litter size, nocturnal movements, and den placement all were similar among risk categories. Nocturnal locations of foxes were closer to roads than were den locations, and den fidelity was lowest for medium-risk foxes and highest for low-risk foxes but intermediate for high-risk foxes. Food availability and use were not affected by proximity to roads. We were unable to detect any significant detrimental effects from 2-lane roads on kit fox demography and ecology. Our results suggest that standard mitigation strategies, such as crossing structures and exclusionary fencing, would not benefit kit foxes on the LNA.     

Is the enigma a variation? Sagina boydii F. B. White (Caryophyllaceae), Boyd's pearlwort

Sagina boydii F. B. White (Caryophyllaceae), Boyd's pearlwort, is an enigmatic taxon of unknown geographical origin which is only known in cultivation and is of uncertain taxonomic status. Morphological, cytological and geographical evidence suggests that it is most similar to S. procumbens L. and S. saginoides (L.) H. Karst., but it differs in its compact growth form. Genetically, AFLP analysis shows that it can be included as part of the variation in S. procumbens . In cultivation, it will grow true from seed. Other compact growth forms occur in S. procumbens but do not grow true from seed. As S. boydii is part of the variation in S. procumbens , is of uncertain geographical origin, is known only in cultivation, and grows true from seed, it is best treated as a new cultivar, Sagina procumbens 'Boydii'. A neotype and standard specimen is designated.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 147 , 203–211.     

Isolation of 18 polymorphic microsatellite loci from the North American red squirrel,Tamiasciurus hudsonicus (Sciuridae,Rodentia), and their cross‐utility in other species

We isolated 18 polymorphic microsatellite loci to be used for pedigree analysis in a wild population of North American red squirrels, Tamiasciurus hudsonicus. Allelic diversity and observed heterozygosity ranged from six to 13 and 0.39 to 0.89, respectively, in a sample of 93 individuals. Up to 13 sets of primers also amplify in other rodent species.     

Leaf gas exchange and nitrogen dynamics of N2-fixing, field-grown Alnus glutinosa under elevated atmospheric CO2

Few studies have investigated the effects of elevated CO₂ on the physiology of symbiotic N₂-fixing trees. Tree species grown in low N soils at elevated CO₂ generally show a decline in photosynthetic capacity over time relative to ambient CO₂ controls. This negative adjustment may be due to a reallocation of leaf N away from the photosynthetic apparatus, allowing for more efficient use of limiting N. We investigated the effect of twice ambient CO₂ on net CO₂ assimilation (A), photosynthetic capacity, leaf dark respiration, and leaf N content of N2-fixing Alnus glutinosa (black alder) grown in field open top chambers in a low N soil for 160 d. At growth CO₂, A was always greater in elevated compared to ambient CO₂ plants. Late season A vs. internal leaf p(CO₂) response curves indicated no negative adjustment of photosynthesis in elevated CO₂ plants. Rather, elevated CO₂ plants had 16% greater maximum rate of CO₂ fixation by Rubisco. Leaf dark respiration was greater at elevated CO₂ on an area basis, but unaffected by CO₂ on a mass or N basis. In elevated CO₂ plants, leaf N content (μg N cm^?2) increased 50% between Julian Date 208 and 264. Leaf N content showed little seasonal change in ambient CO₂ plants. A single point acetylene reduction assay of detached, nodulated root segments indicated a 46% increase in specific nitrogenase activity in elevated compared to ambient CO₂ plants. Our results suggest that N₂-fixing trees will be able to maintain high A with minimal negative adjustment of photosynthetic capacity following prolonged exposure to elevated CO₂ on N-poor soils.     

Inhibition of Reproduction in <Emphasis Type="Italic">Trypanosoma lewisi</Emphasis> by Ouabain

Trypanosoma lewisi usually produces a benign parasitaemia in rats. The parasites multiply only during the first few days after infection. Reproducing populations contain organisms that vary greatly in shape, size and total length. The coefficient of variation (CV) of the total length of the parasites measures this variability and is a sensitive index of reproductive activity¹. The CV is high, about 25%, early in the infection when reproduction is intense and thereafter decreases during infection until the trypanosomes become nearly uniform in size at about the tenth day of infection after which mostly non-reproducing forms are found².     

Selection for and against insecticide resistance and possible methods of inhibiting the evolution of resistance in mosquitoes

Abstract. 1. From published data on the rate of build-up of insecticide resistance in wild populations of Anopheles culicifacies and An.stephensi , calculations have been made of the coefficients of selection which would be required to produce these rates of evolution. It is assumed in turn that the resistances might be effectively dominant, recessive or intermediate.
2. The results in the case of DDT resistance in An.culicifacies indicated that the fitness of resistant individuals was 1.28–1.51 × that of susceptibles.
3. Published data have also been examined with reference to the reversions towards susceptibility which occurred when spraying has been withdrawn. The coefficients of selection against resistance, which would be required to produce the observed rates of reversion, have been calculated. In the case of An.culicifacies and DDT these coefficients were found to be inversely related to the initial frequency of the susceptibility gene.
4. The coefficients of selection have been used to assess the feasibility of inhibiting the evolution of resistance by spraying different insecticides in the alternate sectors of a grid pattern and/or periodically releasing susceptible males. If the proportion of migrants from sector to sector were 15–30%, a "grid" system would considerably reduce the rate of evolution of resistance, but to prevent resistance from ultimately building up to high levels periodic releases would also be required. These releases need not be frequent (approximately during one month each year) if resistance is effectively recessive in the field.     

Are there effective resistance management strategies for vectors of human disease?*

The rotation of insecticides used by the Onchocerciasis Control Programme in West Africa is reviewed and the motives for this rotation are shown to be not only management of temephos resistance in the Simulium vectors but also constraints on what compounds are usable at particular seasons. A computer model indicates that without these seasonal constraints there is unlikely to be an advantage in a pre-planned rotation of insecticides, as compared with the prompt switching of compounds as dictated by detection of build up of resistance and switching back to the original compound if the regression of resistance is found to give the opportunity to do so. The latter sequence of events can hardly be called a ‘strategy’ for resistance management, but is what any well-managed pest control programme would be expected to do. The use of an insecticide mixture is different in principle from the use of rotation and depends on the idea that if the mixture is used from the outset, when resistance to both components of the mixture is likely to be rare, the double resistance combination would be so rare as to be dwarfed in numbers by those insects which avoid exposure altogether. The prospects for successful use of a mixture depend on each component killing a very high percentage of the exposed insects which are genetically susceptible to it. Whether this condition is met could be tested, for example, in the case of exposure of mosquitoes to insecticide-treated bednets.