Pleometrosis in phyllode-glueing thrips (Thysanoptera: Phlaeothripidae) on Australian Acacia

Pleometrosis, or colony founding by more than one female, is common in various social insects and it engenders opportunities for social cooperation as well as cheating. The life cycles of four species of thrips on Australian Acacia trees were examined to elucidate the extent and nature of colony founding by multiple individuals. Data from colonies of three species of thrips from the genus Dunatothrips Moulton and one species of Lichanothrips Mound were used to infer the prevalence of pleometrosis in each species. The results indicate that Dunatothrips species show high levels of cofounding, with up to 50% of colonies having more than one foundress. By contrast, colonies of Lichanothrips are predominantly established by a female and a male. As in some communal insects, pleometrosis is facultative in Dunatothrips , foundresses show more or less constant per capita reproduction with foundress number, and the selective pressures for pleometrosis may involve predation pressure during founding or survivorship insurance for the brood. In Lichanothrips , male founders are probably engaging in mate guarding, which also occurs in some species of gall-inducing thrips on Acacia . The differences in founding patterns between Dunatothrips and Lichanothrips may be due in part the nature of their domiciles: Dunatothrips engage in extensive construction of a domicile using anal secretions, whereas many Lichanothrips primarily improve a pre-existing partial enclosure. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 75 , 467–474.     

Reproductive hierarchies in the African allodapine bee Allodapula dichroa (Apidae: Xylocopinae) and ancestral forms of sociality

The social organization of allodapine bees has been described in detail for most genera, although there remains a notable gap for one major lineage, the genus Allodapula . Here, we provide the first detailed study of social organization in Allodapula dichroa . Colony sizes are small and the frequency of cooperative nesting is low compared with other allodapine taxa, but there is very clear evidence for reproductive differentiation among adult nestmates. Reproductively dominant females tend to be larger than their nestmates and have much higher levels of wing wear, suggesting that they perform most foraging activities. Multi-female colonies have: (1) lower rates of complete brood absence, suggesting a substantial benefit to cooperative nesting; and (2) larger numbers of brood, suggesting that the presence of a second adult female leads to a greater reproductive output. These data suggest a major phylogenetic split in the form of social organization within the allodapines. In the genus Macrogalea (sister clade to all other allodapines), body size does not preclude young females from laying eggs, and there appears to be, at most, weak reproductive queues. However, in most other allodapines, reproductive hierarchies are prominent and younger and/or smaller females queue for reproductive opportunities, adopt permanently subordinate roles, or disperse. Interestingly, the most common forms of reproductive hierarchies in allodapines do not involve subordinates undertaking foraging roles before reproduction, but instead involve the delaying of both reproduction and foraging. This has implications for the understanding of suggested developmental ground plans in the early stages of social evolution.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 520–530.     

Modelled effects of precipitation on ecosystem carbon and water dynamics in different climatic zones

The ongoing changes in the global climate expose the world's ecosystems not only to increasing CO₂ concentrations and temperatures but also to altered precipitation (P) regimes. Using four well-established process-based ecosystem models (LPJ, DayCent, ORCHIDEE, TECO), we explored effects of potential P changes on water limitation and net primary production (NPP) in seven terrestrial ecosystems with distinctive vegetation types in different hydroclimatic zones. We found that NPP responses to P changes differed not only among sites but also within a year at a given site. The magnitudes of NPP change were basically determined by the degree of ecosystem water limitation, which was quantified here using the ratio between atmospheric transpirational demand and soil water supply. Humid sites and/or periods were least responsive to any change in P as compared with moderately humid or dry sites/periods. We also found that NPP responded more strongly to doubling or halving of P amount and a seasonal shift in P occurrence than that to altered P frequency and intensity at constant annual amounts. The findings were highly robust across the four models especially in terms of the direction of changes and largely consistent with earlier P manipulation experiments and modelling results. Overall, this study underscores the widespread importance of P as a driver of change in ecosystems, although the ultimate response of a particular site will depend on the detailed nature and seasonal timing of P change.     

Crustecdysone Mediated Changes in Crayfish

Molting in crayfish, essential for growth is preceded by a decreasein total organic content during premolt. Mineral, as calcium,is conserved in gastroliths after mobilization from the exoskeleton.Crustecdysone treatment results in gastrolith formation by intactcrayfish in intermolt, state C, but does not influence the rateof gastrolith formation in eyestalkless animals. Moreover, therate of gastrolith formation is not increased at higher hormonedoses; conversely, less dense, abnormal gastrohths result, whileapolysis is evident by 48 to 60 hours after treatment. It appearsthat crustecdysone promotes reabsorption of the organic matrixsince treatment with this hormone does not lead to a measureabledecrease in calcium content of shell based on dry weight. Premolt crayfish normally have a higher amino acid pool in alltissues than do those in intermolt, and eyestalk removal fromintermolt crayfish results in an increase in the free-aminoacid level of all tissues by 24 hours; crustecdysone treatmentresults in a significant increase in muscle amino acids by 12hours after a hormone dose of 5 µg/g body weight. In thecontext of integumentary growth and protein synthesis low dosesof crustecdysone (1 µg/g) increase the in vivo incorporationof amino acid into hypodermis, but not hepatopancreas, by 24hours, and the increase is significant by 36 hours; a higherdose (5 µg) does not change this rate of incorporation.Selective increase in hypodermis protein is not evident in acidphosphatase levels from 12 to 48 hours, but respiration of thistissue is significantly elevated within two hours after hormoneinjection.     

Studies on the laboratory mating habits of the mosquito Culex pipiens

The variation in copulatory activity in three strains of Culex pipiens is investigated and the results are discussed in relation to genetic control of mosquito populations.     

The Hydraulic Principle

SYNOPSIS. AS theory rules method, the methodological proceduresapplied to morphological explanation have to be derived fromthe law-like properties of the objects under investigation.The explanation of organismic constructions has to be basedon the hydraulic principle which describes organisms as systemscomposed of fluid contained within flexiblemembranes. This insightestablishes a supra-molecular causal principle which, in itsgenerality for morphological explanation, parallels the biochemicalprinciples of molecular biology on the molecular level. Everyform and architectural arrangement has to be conceived as theresult of the form-enforcing influence of mechanical elementsthat operatewithin an integrated mechanically coherent system.An adequate explanation of morphological configuration has toelaborate the organization of the constructional whole and explainits properties as the result of a gradual transformation processthat is constrained by internal mechanical principles. The theoriesdeveloped by such a procedure are open to criticism and canbe tested and corroborated by reference to experiments conductedby nature.     

Circadian rhythm of the locomotor activity in Drosophila melanogaster and its mutants 'sine oculis' and 'small optic lobes'

ABSTRACT. The locomotor activity patterns of wildtype Drosophila melanogaster and the mutants so (sine oculis) and sol (small optic lobes) were investigated. In all strains the proportions showing circadian rhythmicity, arrhythmicity and more complex patterns which could not be thus classified were similar. The occurrence of abnormal activity patterns is thus not a property of the mutation as previously claimed (Mack & Engelmann, 1981). In flies with a distinct circadian rhythmicity, the period lengths (τ) varied between strains, τ for wildtype Italy and the mutant so was longer than for wildtype Berlin and the mutant sol. As different τ's have been reported by others, τ does not seem to be closely determined for Drosophila melanogaster. Many flies exhibited two rhythms simultaneously, one with τ shorter and one with τ longer than 24 h, apparently implying two-oscillator control of the locomotor activity. The eyeless so mutants were entrained by LD cycles, so the compound eyes are not necessary, and so must possess the relevant photoreceptor(s) elsewhere. This may therefore also be true for the wildtype. Histology of the so adults revealed no correlation between the degree of reduction in the medulla and the occurrence of abnormal activity patterns. Since the only structures common to the medulla of so and sol are known to be large tangential cells, it is concluded that either they are of importance for the rhythmic system, or the oscillator(s) controlling locomotor activity is (are) not located in the medulla.