Effects of dietary nicotine on the development of an insect herbivore, its parasitoid and secondary hyperparasitoid over four trophic levels

Abstract.  1. Allelochemicals in herbivore diet are known to affect the development of higher trophic levels, such as parasitoids and predators.
2. This study examines how differing levels of nicotine affects the development of a herbivore, its parasitoid and secondary hyperparasitoid over four trophic levels. Separate cohorts of the herbivore, Manduca sexta , were fed on artificial diets containing 0.0, 0.1, and 0.5% wet weights of nicotine. Some of the larvae in each cohort were separately parasitised in the first (L1) and third (L3) instars by the gregarious endoparasitoid, Cotesia congregata . Newly emerged parasitoid cocoons were, in turn, parasitised by the hyperparasitoid, Lysibia nana .
3. Pupal mass in M . sexta was negatively correlated with nicotine concentrations in the artificial diet, although larval development time was unaffected.
4. Hyperparasitoid survival was highest when there were low levels of nicotine in the diet of M . sexta . Cocoon mass in C . congregata and adult mass in L . nana were mostly affected by nicotine levels in host diet when L1 M. sexta larvae were parasitised. The effects were slightly stronger on L . nana than on C . congregata , indicating the presence of both qualitative and quantitative effects of nicotine concentration on both species.
5. The results suggest that allelochemicals in herbivore diet can have both direct and indirect effects on the performance of higher trophic levels. However, in multitrophic interactions these effects can vary with the stage of the herbivore attacked by the primary parasitoid, as well as with the strategy employed by the herbivore to deal with plant phytotoxins.     

Global warming and positive fitness response in mountain populations of common lizards Lacerta vivipara

Recent global warming threatens many species and has already caused population‐ and species‐level extinctions. In particular, high risks of extinction are expected for isolated populations of species with low dispersal abilities. These predictions rely on widely used ‘climatic envelope’ models, while individual responses, the ultimate driver of a species response to climate change, have been most often neglected. Here, we report on some changes in life‐history traits of a dispersal‐limited reptile species (a poorly studied taxa) living in isolated populations. Using long‐term data on common lizards collected in southern France, we show that individual body size dramatically increased in all the four populations studied over the past 18 years. This increase in body size in all age classes appeared related to a concomitant increase in temperature experienced during the first month of life (August). Daily maximum temperature in August increased by 2.2°C and yearling snout‐vent‐length increased by about 28%. As a result, adult female body size increased markedly, and, as fecundity is strongly dependent on female body size, clutch size and total reproductive output also increased. For one population where capture–recapture data were available, adult survival was positively related to May temperature. All fitness components investigated therefore responded positively to the increase in temperature, such that it might be concluded that the common lizard has been advantaged by the shift in temperature. We contrast these short‐term results with the long‐term habitat‐based prediction that these populations located close to mountain tops on the southern margin of the species range should be unable to cope with the alteration of their habitat. To achieve a better prediction of a species persistence, one will probably need to combine both habitat and individual‐based approaches.     

Aspects of the functional morphology in the cranial and cervical skeleton of the sabre-toothed cat Paramachairodus ogygia (Kaup, 1832) (Felidae, Machairodontinae) from the Late Miocene of Spain: implications for the origins of the machairodont killing bite

The skull and cervical anatomy of the sabre-toothed felid Paramachairodus ogygia (Kaup, 1832) is described in this paper, with special attention paid to its functional morphology. Because of the scarcity of fossil remains, the anatomy of this felid has been very poorly known. However, the recently discovered Miocene carnivore trap of Batallones-1, near Madrid, Spain, has yielded almost complete skeletons of this animal, which is now one of the best known machairodontines. Consequently, the machairodont adaptations of this primitive sabre-toothed felid can be assessed for the first time. Some characters, such as the morphology of the mastoid area, reveal an intermediate state between that of felines and machairodontines, while others, such as the flattened upper canines and verticalized mandibular symphysis, show clear machairodont affinities.  © 2005 The Linnean Society of London, Zoological Journal of the Linnean Society , 2005, 144 , 363−377.     

Antagonistic Action of the Bacterium Bacillus Licheniformis M-4 Toward the Amoeba Naegleria Fowleri

ABSTRACT. Free-living amoebae belonging to the species Naegleria fowleri are known to be the etiological agents for a form of fulminant meningoencephalitis that is generally fatal (primary amoebic meningoencephalitis). In a broad bacterial screening from soil and water we have isolated three strains (M-4, D-13 and A-12) belonging to the species Bacillus licheniformis that have remarkable amoebicidal activity against Naegleria sp. and also against different Gram-positive and Gram-negative bacteria. Physical-chemical characteristics, partial purification and biological activities of a substance produced by the M-4 strain have been investigated. This substance (m-4) is stable at high temperature (up to 100°C) and extremes of pH (2.5-9.5) and also at -20°C for months. Its production is greatly influenced by oxygenation of the cultures and is probably related to the sporulation process of the bacterium. Scanning electron microscope observations reveal that amoebae are lysed after a few minutes contact with m-4.     

Effect of Nitrate on Components of Nodule Leghaemoglobins

Multiple components of leghaemoglobins (Lbs) from several legumespecies have been separated by polyacrylamide gel electrophoresis(PAGE), and identified by densitometry at 405 nm, extractionfrom gels and formation of their respective CO-ferrous complexes.Components were numbered consecutively starting from the anodeside, and their relative concentrations were calculated by densitometryin control and -treated nodules. The number of Lb components was five in Pisum sativum, four in Glycinemax, at least two in Lupinus luteus and Trifolium repens, andtwo in Vigna radiata and V. unguiculata. Only one componentwas detected in fresh nodules of Phaseolus vulgaris. Nitratesignificantly reduced the total content of Lb in all legumes,except Lupinus, the extent of reduction varying with the species.It also had a major effect on the proportions of components,causing an inversion in the relative abundance of Lb I and LbII of V. radiata: the concentration of Lb I increased from 8%to 81% with application, while total Lb only decreased by 13%. Drastic changes in proportions of Lbcomponents were not artifactual and cannot be attributed exclusivelyto different turnover rates. They should correspond to variationsin biosynthesis of the various components, probably originatingat the genetic level. Key words: Leghaemoglobin components, nitrate, nodule senescence     

Behaviour of male and female parasitoids in the field: influence of patch size,host density,and habitat complexity

1. Two field experiments were carried out to examine the role of patch size, host density, and complexity of the surrounding habitat, on the foraging behaviour of the parasitoid wasp Cotesia glomerata in the field. 2. First, released parasitoids were recaptured on patches of one or four Brassica nigra plants, each containing 10 hosts that were placed in a mown grassland area. Recaptures of females were higher than males, and males and females aggregated at patches with four plants. 3. In experiment 2, plants containing 0, 5 or 10 hosts were placed in unmown grassland plots that differed in plant species composition, on bare soil, and on mown grassland. Very low numbers of parasitoids were recaptured in the vegetated plots, while high numbers of parasitoids were recaptured on plants placed on bare soil or in mown grassland. Recaptures were higher on plants on bare soil than on mown grassland, and highest on plants containing 10 hosts. The host density effect was significantly more apparent in mown grassland than on bare soil. 4. Cotesia glomerata responds in an aggregative way to host density in the field. However, host location success is determined mostly by habitat characteristics, and stronger host or host‐plant cues are required when habitat complexity increases.     

Arboreal substrates influence foraging in tropical ants

1. Physically complex substrates impart significant costs on cursorial central‐place foragers in terms of time spent outside the nest and total distance travelled. Ants foraging in trees navigate varied surfaces to access patchy resources, thus providing an appropriate model system for examining interactions between foraging efficiency and substrates. 2. We expected that the speed of recruitment, body size distribution and species richness of foraging arboreal ants would differ predictably among common substrate types occurring on tropical tree trunks. We measured changes in ant abundance and species composition over time at baits placed on bare tree bark, moss‐covered bark, and vine‐like vegetation appressed to bark. We also measured average body size and body size frequency on the three substrate types. Ants discovered baits sooner and accumulated at baits relatively faster when using vine substrates as the primary foraging trail. Average body size was smaller on vine substrates than on bark. Experimental removal of vine and moss substrates nullified these differences. Contrary to our predictions, species richness and body size distributions did not differ among the three substrate types, due in part to the frequent presence of a few common ground‐nesting species at baits on bare bark. 3. Our results collectively indicate that linear substrates facilitate access of foraging ants to patchy resources. Ant use of vine‐like substrates appears to be opportunistic; vine use is not confined to certain species nor constrained by body size.     

Stress promotes changes in resource allocation to growth and reproduction in a simultaneous hermaphrodite with indeterminate growth

In iteroparous animals, investment in growth is compromised by investment in reproduction, especially in species with indeterminate growth. Life‐history theory predicts that growth should be favoured over reproduction, assuming size‐related fecundity or survival. Hence, increase body condition represents an increase in reproductive potential. Simultaneous hermaphrodites should adjust their resource allocation to each sex function in response to current conditions but, recently, it has been suggested that, in hermaphrodites, gender allocation should be considered as a three‐way trade‐off, including the investment in somatic growth. Due to the higher costs involved, the female function is affected to a greater extent by environmentally stressful conditions rather than the male function. To examine this, we induced stress in the hermaphroditic earthworm Eisenia fetida (Savigny, 1826) and looked for changes in resource allocation in nonreproductive and reproductive individuals. Experimental stress was induced by using tweezers to elicit contractile escape movements. We predicted that stressed earthworms would preferentially allocate resources to growth. In nonreproductive individuals, however, stress had a negative effect on growth, although weight recovery was rapid once manipulation ceased, indicating the importance of body condition, as well as the existence of mechanisms of compensatory growth for growth trajectories in this earthworm species. The response of reproductive individuals was consistent with our expectation: (1) stressed worms maintained their growth rate at the expense of current reproduction and (2) stressed earthworms laid 25% fewer cocoons, which were 30% lighter than cocoons laid by control earthworms. The present results suggest that E. fetida regulates its reproductive effort and that future reproduction has more impact on its fitness than current reproduction. The trade‐off between current and future reproduction should be taken into consideration in models of sex allocation in simultaneous hermaphrodites. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 91 , 593–600.     

Determining the effects of habitat management and climate on the population trends of a declining steppe bird

The Little Bustard Tetrax tetrax is one of the most threatened steppe bird species in Europe, due mainly to agricultural intensification. Despite the relative importance of the Iberian population (approximately 50% of the global population) little is known about its dynamics and trends, especially in core distribution areas. This study evaluates the influences of meteorological factors and land management on the oscillations and medium-term trends of two Little Bustard populations in Central Spain. During 2001–2007, surveys of breeding male and female Little Bustards were carried out in two central Spanish locations: Valdetorres, in Special Protection Area (SPA) no. 139 (1600 ha), and Campo Real, in Important Bird Area (IBA) no. 075 (1150 ha). Densities were 3.3–4.0 and 1.1–2.1 males/km² in Campo Real, and 1.8–2.2 and 0.6–1.3 females/km² in Valdetorres. The sex ratio was biased towards males in both cases. Both populations declined during 2001–2007, especially in Valdetorres (60%). Variation in habitat composition did not explain variation in the numbers of males. Both populations were influenced by total precipitation in the preceding October–May period. Results suggest that the Little Bustard may be sensitive to future climate trends in Europe. Finally, different simulated demographic scenarios suggest that low female survival and productivity may be the immediate cause of the decline in Little Bustard populations, which is consistent with their sensitivity to climatic conditions.