Is there genetic structure in populations of Helicoverpa armigera from Australia?

Recent studies suggest that populations of the pest moth Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) may be genetically differentiated over short distances and time periods within Queensland, Australia. To test for genetic structure in another region of Australia, we characterized population differentiation in Victorian samples of H. armigera using eight microsatellite loci. We found no evidence of genetic structure among samples from different locations or among samples collected at different times. Moreover, Victorian samples were not differentiated from other samples of H. armigera from Queensland and New Zealand. All samples showed substantial deviations from Hardy–Weinberg equilibrium, suggesting a high frequency of null alleles typically found in microsatellites of Lepidoptera. These results indicate that populations of H. armigera are not strongly structured among regions in south‐eastern Australia.     

Multi‐locus phylogeny of African pipits and longclaws (Aves: Motacillidae) highlights taxonomic inconsistencies

The globally distributed avian family Motacillidae consists of five to seven genera (Anthus, Dendronanthus, Tmetothylacus, Macronyx and Motacilla, and depending on the taxonomy followed, Amaurocichla and Madanga) and 66–68 recognized species, of which 32 species in four genera occur in sub‐Saharan Africa. The taxonomy of the Motacillidae has been contentious, with variable numbers of genera, species and subspecies proposed and some studies suggesting greater taxonomic diversity than currently recognized (five genera and 67 species). Using one nuclear (Mb) and two mitochondrial (cyt b and CO1) gene regions amplified from DNA extracted from contemporary and museum specimens, we investigated the taxonomic status of 56 of the currently recognized motacillid species and present the most taxonomically complete and expanded phylogeny of this family to date. Our results suggest that the family comprises six clades broadly reflecting continental distributions: sub‐Saharan Africa (two clades), the New World (one clade), Palaearctic (one clade), a widespread large‐bodied Anthus clade, and a sixth widespread genus, Motacilla. Within the Afrotropical region, our phylogeny further supports recognition of Wood Pipit Anthus nyassae as a valid species, and the treatment of Long‐tailed Pipit Anthus longicaudatus and Kimberley Pipit Anthus pseudosimilis as junior subjective synonyms of Buffy Pipit Anthus vaalensis and African Pipit Anthus cinnamomeus, respectively. As the disjunct populations of Long‐billed Pipit Anthus similis in southern and East Africa are genetically distinct and geographically separated, we propose a specific status for the southern African population under the earliest available name, Nicholson's Pipit Anthus nicholsoni. Further, as our analyses indicate that Yellow‐breasted Pipit Anthus chloris and Golden Pipit Tmetothylacus tenellus are both nested within the Macronyx longclaws, we propose transferring these species to the latter genus.     

Solar Radiation during Rewarming from Torpor in Elephant Shrews: Supplementation or Substitution of Endogenous Heat Production?

Many small mammals bask in the sun during rewarming from heterothermy, but the implications of this behaviour for their energy balance remain little understood. Specifically, it remains unclear whether solar radiation supplements endogenous metabolic thermogenesis (i.e., rewarming occurs through the additive effects of internally-produced and external heat), or whether solar radiation reduces the energy required to rewarm by substituting (i.e, replacing) metabolic heat production. To address this question, we examined patterns of torpor and rewarming rates in eastern rock elephant shrews (Elephantulus myurus) housed in outdoor cages with access to either natural levels of solar radiation or levels that were experimentally reduced by means of shade cloth. We also tested whether acclimation to solar radiation availability was manifested via phenotypic flexibility in basal metabolic rate (BMR), non-shivering thermogenesis (NST) capacity and/or summit metabolism (M_sum). Rewarming rates varied significantly among treatments, with elephant shrews experiencing natural solar radiation levels rewarming faster than conspecifics experiencing solar radiation levels equivalent to approximately 20% or 40% of natural levels. BMR differed significantly between individuals experiencing natural levels of solar radiation and conspecifics experiencing approximately 20% of natural levels, but no between-treatment difference was evident for NST capacity or M_sum. The positive relationship between solar radiation availability and rewarming rate, together with the absence of acclimation in maximum non-shivering and total heat production capacities, suggests that under the conditions of this study solar radiation supplemented rather than substituted metabolic thermogenesis as a source of heat during rewarming from heterothermy.     

The Drosophila heat shock hsr-omega gene: an allele frequency cline detected by quantitative PCR.

The hsr-omega gene of Drosophila melanogaster produces RNA products both constitutively and at elevated levels in response to heat stress. A single-nucleotide difference in this gene that has been detected using denaturing gradient gel electrophoresis (DGGE) is responsible for an hsr-omegaa/b polymorphism, and selection experiments have indicated an association between the hsr-omegaa allele and susceptibility to heat stress. Since allele frequency estimates for population surveys using PCR and DGGE for single flies would be relatively time-consuming and expensive, we here develop a quantitative competitive-PCR method using mass-grind genomic DNA preparations for this purpose. Geographical and temporal variation of allele frequency at the hsr-omega locus in Australian populations of D. melanogaster are examined. Regular samples from a southern population through a summer season suggested stability of hsr-omegaa frequency. Field populations sampled from a approximately 2,250 km north-south transect along eastern Australia revealed a strong positive association between the frequency of hsr-omegaa and latitude, and marked spatial autocorrelation. Using appropriate analyses, strong association between population differences in hsr-omegaa frequencies and differences in temperature and rainfall measures, after controlling for latitudinal differences, support the idea that the cline in hsr-omegaa frequency may be attributable to some form of climatic selection.     

Cardiac dilatation and pump dysfunction without intrinsic myocardial systolic failure following chronic beta-adrenoreceptor activation

There is no direct evidence to indicate that pump dysfunction in a dilated chamber reflects the impact of chamber dilatation rather than the degree of intrinsic systolic failure resulting from myocardial damage. In the present study, we explored the relative roles of intrinsic myocardial systolic dysfunction and chamber dilatation as mediators of left ventricular (LV) pump dysfunction. Administration of isoproterenol, a beta-adrenoreceptor agonist, for 3 mo to rats (0.1 mg.kg(-1).day(-1)) resulted in LV pump dysfunction as evidenced by a reduced LV endocardial fractional shortening (echocardiography) and a decrease in the slope of the LV systolic pressure-volume relation (isolated heart preparations). Although chronic beta-adrenoreceptor activation induced cardiomyocyte damage (deoxynucleotidyl transferase-mediated dUTP nick-end labeling) as well as beta(1)- and beta(2)-adrenoreceptor inotropic downregulation (attenuated contractile responses to dobutamine and salbutamol), these changes failed to translate into alterations in intrinsic myocardial contractility. Indeed, LV midwall fractional shortening (echocardiography) and the slope of the LV systolic stress-strain relation (isolated heart preparations) were unchanged. A normal intrinsic myocardial systolic function, despite the presence of cardiomyocyte damage and beta-adrenoreceptor inotropic downregulation, was ascribed to marked increases in myocardial norepinephrine release, to upregulation of alpha-adrenoreceptor-mediated contractile effects as determined by phenylephrine responsiveness, and to compensatory LV hypertrophy. LV pump failure was attributed to LV dilatation, as evidenced by increased LV internal dimensions (echocardiography), and a right shift and increased volume intercept of the LV diastolic pressure-volume relation. In conclusion, chronic sympathetic stimulation, despite reducing beta-adrenoreceptor-mediated inotropic responses and promoting myocyte apoptosis, may nevertheless induce pump dysfunction primarily through LV dilatation, rather than intrinsic myocardial systolic failure.