Thermal phenotypic plasticity of body size in <Emphasis Type="Italic">Drosophila melanogaster</Emphasis>: sexual dimorphism and genetic correlations

Thirty isofemale lines collected in three different years from the same wild French population were grown at seven different temperatures (12–31°C). Two linear measures, wing and thorax length, were taken on 10 females and 10 males of each line at each temperature, also enabling the calculation of the wing/thorax (W/T) ratio, a shape index related to wing loading. Genetic correlations were calculated using family means. The W–T correlation was independent of temperature and on average, 0.75. For each line, characteristic values of the temperature reaction norm were calculated, i.e. maximum value, temperature of maximum value and curvature. Significant negative correlations were found between curvature and maximum value or temperature of maximum value. Sexual dimorphism was analysed by considering either the correlation between sexes or the female/male ratio. Female–male correlation was on average 0.75 at the within line, within temperature level but increased up to 0.90 when all temperatures were averaged for each line. The female/male ratio was genetically variable among lines but without any temperature effect. For the female/male ratio, heritability (intraclass correlation) was about 0.20 and evolvability (genetic coefficient of variation) close to 1. Although significant, these values are much less than for the traits themselves. Phenotypic plasticity of sexual dimorphism revealed very similar reaction norms for wing and thorax length, i.e. a monotonically increasing sigmoid curve from about 1.11 up to 1.17. This shows that the males are more sensitive to a thermal increase than females. In contrast, the W/T ratio was almost identical in both sexes, with only a very slight temperature effect.     

NEW PERMINERALIZED FLORA AND TRILOBITES FROM THE MID TOURNAISIAN (EARLY CARBONIFEROUS) RUXTON FORMATION, CLARKE RIVER BASIN, NORTH-EAST AUSTRALIA

Abstract:  An association of a new permineralized flora with preserved anatomy and decalcified trilobite remains is described from early crenulata Zone (mid Tournaisian; Early Carboniferous) calcareous siltstones in a predominantly shale and minor limestone sequence low in the Ruxton Formation of the eastern Clarke River Basin, north-east Queensland. Whereas the trilobites belong to Linguaphillipsia , a common and diversified taxon in eastern Australia, the plants (with the exception of Stauropteris that was earlier identified from the Burdekin Basin) were known previously only from the Mississipian (Lower Carboniferous) of Western Europe. The plants represent a diverse assemblage comprising lycopsids, cladoxylaleans, a variety of fern rachises and seed plants, including stems ( Tristichia -type), Lyginorachis petioles and a new cupule, Ruxtonia minuta gen. et sp. nov., containing Hydrasperma ovules.     

SONGS OF BLUE TITS PARUS CAERULEUS PALMENSIS FROM LA PALMA (CANARY ISLANDS)—A TEST OF HYPOTHESES

ABSTRACT

Parus major and Parus caeruleus palmensis have some song types in common. They consist of whistled element-types in different frequency ranges. Both species show territorial reactions to playback of the song-types belonging to the other species. P.c. palmensis does not share any songtypes with Central European Parus caeruleus. This is confirmed by playback experiments with the different song types, which do not elicit any territorial behaviour. The songs of P.c. palmensis also differ from those of blue tits from any other Canary Island. They may be derived from contact calls of the Lanzarote population. They have been developed by young birds that had not yet learnt their songs when they colonized La Palma from Lanzarote without reaching any of the other Canary Islands. It is suggested that the uniform song repertoire was developed by adapting the already learned contact calls to each other. The similarities to song types of P. major are due to convergence rather than character displacement. All other Canary Island tit populations share the main features of their songs, which are characterized by quick frequency changes. It seems most likely that these islands have been colonized by birds which had already learnt their songs. Differences in song repertoires are mainly caused by drift events which happen to occur because of population bottlenecks during the colonization process.     

The phenology of Syrphidae (Diptera): are they Batesian mimics of Hymenoptera?

The phenology of aculeate Hymenoptera and of syrphids which are believed to mimic them has been investigated at three semi-natural ancient woodland sites in north-west England. It is concluded that the abundance and phenology of most of the hoverflies is consistent with their being Batesian mimics of particular species of bee or wasp. The main exceptions are Eristalis spp., Helophilus spp., Syrphus spp. and Episyrphus balteatus which are often much more abundant than their supposed models. These four taxa may still benefit from mimicry, but further research is needed to confirm this. With the possible exceptions of Eristalis pertinax and E. tenax , there is no strong evidence from north-west England in support of Waldbauer's hypothesis that mimics are rare when fledgling birds are abundant but may be commoner in autumn and spring. The data also indicate that mimics which closely resemble their models (specific mimics) are usually rarer than their models, whereas mimics with a less precise resemblance (non-specific mimics) are often commoner than models.     

The Influence of Carbohydrate Reserves on the Response of Nodulated White Clover to Defoliation

A growth-chamber study was carried out to determine whetherthe response of apparent nitrogenase activity (C₂ H₂ reduction)to complete defoliation is influenced by the availability ofcarbohydrate reserves Reserve carbohydrate (TNC) concentrationsof 6-week-old white clover (Trifoliun repens L) plants weremodified by CO₂ pretreatments There was no difference in theresponse of apparent nitrogenase activity to defoliation betweenplants with different TNC concentrations C₂H₂ reduction activitydeclined sharply after defoliation and then recovered similarlyin both high- and low-TNC plants Further experiments were conductedto explain the lack of response of apparent nitrogenase activityto TNC levels Bacteroid degradation was ruled out because invitro nitrogenase activity of crude nodule extracts was stillintact 24 h after defoliation Sufficient carbohydrates appearedto be available to the nodules of defoliated plants becauseadding [¹⁴C]glucose to the nutrient solution did not preventthe decline in apparent nitrogenase activity These conclusionswere supported by the finding that an increase in pO₂ aroundthe nodules of defoliated plants completely restored their C₂H₂reduction activity The comparison of the effects of defoliationand darkness suggested that the decrease in apparent nitrogenaseactivity was not related directly to the interruption of photosynthesisIt appears that lack of photosynthates is not the immediatecause of the decline of nitrogen-fixing activity after defoliation White clover, Trifolium repens L, defoliation, nitrogen fixation, regrowth, reserves, carbohydrates, acetylene reduction, nodule extract