Stratification and diel activity of arthropods in a lowland rainforest in Gabon

The abundance, activity and species richness of arthropods, particularly of insect herbivores, were investigated in the upper canopy and understorey of a lowland rainforest at La Makandé, Gabon. In total 14 161 arthropods were collected with beating, flight interception and sticky traps, from six canopy sites, during the day and at night, from mid-January to mid-March 1999. The effects of stratum were most important, representing between 40 and 70% of the explained variance in arthropod distribution. Site effects represented between 20 and 40% of the variance and emphasized the néed for replication of sampling among canopy sites. Time effects (diel activity) explained a much lower percentage of variance (6–9%). The density and abundance of many arthropod taxa and species were significantly higher in the upper canopy than in the understorey. Arthropod activity was also higher during the day than at night. In particular, insect herbivores were 2.5 times more abundant and twice as speciose in the upper canopy than in the understorey, a probable response to the greater and more diverse food resources in the former stratum. Faunal overlap between the upper canopy and understorey was low. The most dissimilar herbivore communities foraged in the understorey at night and the upper canopy during the day. Further, a taxonomic study of a species-rich genus of herbivore collected there (Agrilus , Coleoptera Buprestidae) confirmed that the fauna of the upper canopy was different, diverse and very poorly known in comparison to that of the understorey. Herbivore turnover between day and night was rather high in the upper canopy and no strong influx of insect herbivores from lower foliage to the upper canopy was detected at night. This suggests that insect herbivores of the upper canopy may be resident and well adapted to environmental conditions there.     

Origin and evolution of the endemic Macaronesian Inuleae (Asteraceae): evidence from the internal transcribed spacers of nuclear ribosomal DNA

The tribe Inuleae (Asteraceae) has 10 species endemic to the Macaronesian islands, including the three endemic genera Allagopappus, Schizogyne, and Vierea. Phylogenetic analyses of DNA sequence data from the internal transcribed spacers (ITS) of the nuclear ribosomal DNA of 47 taxa were performed using all Macaronesian endemics and representative species from 21 of the 36 genera of the Inuleae. The resulting ITS phylogeny reveals that Allagopappus is sister to a large clade that contains all genera with a predominantly Mediterranean distribution. This finding suggests that Allagopappus may represent an ancient lineage that found refuge in the Canary Islands following the major climatic and/or geologic changes in the Mediterranean basin after the Tertiary. The Macaronesian endemic genus Schizogyne is sister to Limbarda from the Mediterranean. The third Macaronesian endemic genus, Vierea, is sister to Perralderia, which is restricted to Morocco and Algeria. Pulicaria canariensis is sister to P. mauritanica, a species endemic to Morocco and Algeria. In contrast, P. diffusa from the Cape Verde Islands is sister to a broadly distributed species, P. crispa, that occurs from North Africa to the Arabian peninsula. Based on the ITS data, the genera Blumea, Inula, and Pulicaria are not monophyletic. The ITS trees suggested that Blumea mollis belongs to the tribe Plucheeae, a finding that is congruent with recent morphological evidence. A possible southern African origin for the core of the Laurasian taxa of the Inuleae is also suggested.     

House flies delay fungal infection by fevering: at a cost

1. Many ectothermic species have evolved the ability to invoke a ‘behavioural fever’ when infected with a pathogen. The relative costs and benefits of this response, however, have rarely been quantified. 2. The aim of this study was investigate the nature and consequences of behavioural fever in the house fly, Musca domestica L., in response to infection with a possible biocontrol agent, the fungal entomopathogen, Beauveria bassiana (Balsamo) Vuillemin. 3. It was found that infected flies preferred higher temperatures and allocated more effort to thermoregulation than uninfected flies. Flies could not overcome infection but the altered thermal behaviour allowed infected flies to extend their survival and to lay more eggs relative to infected flies maintained under constant conditions. However, flies allowed to fever had lower egg viability suggesting a possible cost. 4. Under the present experimental conditions, the putative costs and benefits fever balanced one another resulting in no net change in fitness. Fever did not, therefore, limit the control potential of the fungus. We discuss whether the costs and benefits of behavioural fever might differ in other ecological contexts.     

Genetic diversity and connectivity of deep‐sea hydrothermal vent metapopulations

Deep‐sea hydrothermal vents provide ephemeral habitats for animal communities that depend on chemosynthetic primary production. Sporadic volcanic and tectonic events destroy local vent fields and create new ones. Ongoing dispersal and cycles of extirpation and colonization affect the levels and distribution of genetic diversity in vent metapopulations. Several species exhibit evidence for stepping‐stone dispersal along relatively linear, oceanic, ridge axes. Other species exhibit very high rates of gene flow, although natural barriers associated with variation in depth, deep‐ocean currents, and lateral offsets of ridge axes often subdivide populations. Various degrees of impedance to dispersal across such boundaries are products of species‐specific life histories and behaviours. Though unrelated to the size of a species range, levels of genetic diversity appear to correspond with the number of active vent localities that a species occupies within its range. Pioneer species that rapidly colonize nascent vents tend to be less subdivided and more diverse genetically than species that are slow to establish colonies at vents. Understanding the diversity and connectivity of vent metapopulations provides essential information for designing deep‐sea preserves in regions that are under consideration for submarine mining of precious metals.     

Abundance Estimation With a Transient Model Under the Robust Design

Abstract: A common situation in capture-mark-recapture (CMR) studies on birds and other organisms is to capture individuals not belonging to the studied population only present during the short time of the capture session. Presence of such transient individuals affects demographic parameter estimation from CMR data. Methods exist to reduce biases on survival estimates in the presence of transients and have been shown to be particularly efficient within the Robust Design framework (several secondary capture sessions within a short time interval during which the studied population can be assumed closed). We present a new model to estimate population size accounting for transients. We first used simulated data to show that the method reduces positive biases due to transients. In a second step, we applied the method to a real CMR dataset on a reed warbler (Acrocephalus scirpaceus) population. Population size estimates are reduced by up to 50% when correcting for the presence of transients. Many field studies on managed animal populations use capture-recapture methodology to obtain crucial parameters of the focal population demography. The resulting data sets are used either to estimate population size ignoring the presence of transients, or to estimate vital rates, accounting for transients but overlooking abundance estimation. Our method conciliates these 2 approaches.     

Differences in the Cyclic AMP-Dependent Phosphorylation of Plasma Membrane Proteins of Differentiated and Undifferentiated L6 Myogenic Cells

Differences in the cyclic AMP-dependent plasma membrane phosphorylation system of undifferentiated and differentiated L₆ myogenic cells have been detected. Endogenous plasma membrane protein phosphorylation in undifferentiated L₆ myoblasts was stimulated more than three fold by 5 × 10⁻⁵ M cyclic AMP, whereas no statistically significant cyclic AMP-dependent phosphorylation of endogenous plasma membrane proteins was observed in differentiated L₆ cells. In undifferentiated cells cyclic AMP promoted the phosphorylation of several proteins, the most prominent of which had a molecular weight of 110,000. In differentiated cells cyclic AMP did not selectively promote the phosphorylation of specific plasma membrane proteins. Both differentiated and undifferentiated L₆ cells, however, contain a cyclic AMP-dependent protein kinase capable of catalyzing the phosphorylation of exogenous substrates, such as histone f₂b. Therefore, the data show that differentiation in L₆ cells is associated with a selective change in the activity of a plasma membrane cyclic AMP-dependent protein kinase which employs endogenous membrane proteins as substrate.     

Geographical distributions,relative abundance and coexistence of Drosophila aldrichi and Drosophila buzzatii in Australia

Abstract Climatic data and collection records for the cactophilic Drosophila aldrichi and Drosophila buzzatii for 97 localities were used to examine the effects of geographical location, season, host plant species and climatic factors on their range and relative abundance. Temporal variation in relative abundance was assessed from monthly collections over 4 years at one locality. Effects of weather variables over the 28 days before each collection were examined. A generalized linear model of the spatial data showed significant geographical variation in relative abundance, and significant climatic effects, with the proportion of D. aldrichi higher in the warm season, and increasing as temperature variation decreased and moisture indices increased. The temporal data gave generally concordant results, as D. aldrichi proportion was higher in summer and autumn, and increased as maximum and minimum temperatures increased, and as variation in maximum temperature decreased. In a laboratory competition experiment, D. aldrichi eliminated D. buzzatii at 31°C, but was itself eliminated at 18°C and 25°C. The range of D. buzzatii is constrained only by availability of its host plant, Opuntia species, although its relative abundance is reduced in the northern part of its distribution. The range of D. aldrichi, from central Queensland to northern NSW, Australia, is entirely within that of D. buzzatii, and its relative abundance decreases from north to south. Both climate and weather, particularly temperature variability, have direct effects on the relative abundances of the two species, and both likely act indirectly by influencing the outcome of interspecific competition.