Evaluating reproductive fitness and metabolic costs for insecticide resistance in Myzus persicae from Chile

The development of insecticide resistance in pest insects is an increasing problem for agriculture, forestry and public health. Aphids are ubiquitous herbivorous insects, with approximately 4700 known species, of which less than 5% exploit the agricultural environment successfully. Of these, the peach‐potato aphid Myzus persicae Sulzer is recognized as one of the most important pests worldwide because it has acquired resistance to many insecticides. Although resistance to insecticides provides important benefits for pests in agricultural fields that are treated with insecticides, it may be associated with fitness (or other) costs in environments that are insecticide free. In the present study, the fitness and energy costs that might be experienced by M. persicae in an insecticide‐free environment when carrying at least one insecticide resistance mutation (IRM), or by having an increased production of esterases, are evaluated. The study investigates whether genotypes that have an IRM also have enhanced esterase production, whether there is any metabolic cost associated with insecticide resistance, and whether there are any fitness costs associated with insecticide resistance and metabolic expenditure. The intrinsic rate of increase, standard metabolic rate (i.e. a measure of maintenance costs) and constitutive esterase activity are determined for 30 different multilocus genotypes carrying (or not carrying) at least one of the two most frequent insecticide resistance mutations (MACE and kdr/super‐kdr) that occur in Chile. The results show that genotypes carrying at least one IRM have higher levels of total esterase activity than genotypes without an IRM, that there is no evidence of an energy cost associated with total esterase activity or IRM, and no evidence for a reproductive fitness cost associated with total esterase activity, IRM or metabolic rate. The results agree with previous studies showing linkage disequilibrium between insecticide resistance mechanisms, although they contrast with those of studies that report fitness costs associated with insecticide resistance in Myzus persicae.     

Tithonia oxfordiana,a new irregular echinoid associated with Jurassic seep deposits in south‐east France

Abstract: The infaunal irregular echinoid, Tithonia oxfordiana, is described and compared to congeneric species previously described from Upper Jurassic and lowermost Cretaceous strata. This new species characterizes a monospecific echinoid assemblage, which occurs only in some places where deep‐marine middle Oxfordian deposits are exposed in south‐east France. Specimens are closely packed and clearly concentrated at the top of small carbonate chemoherms; a close connection of the echinoids with the emission of reduced chemicals, which were oxidized by chemoautotrophic bacteria, is highly probable. Based on general test shape and plate architecture, T. oxfordiana probably was a deposit feeder on chemosynthetic organic matter produced by such bacteria. In view of the fact that T. oxfordiana is the sole species of the Jurassic genus Tithonia known from Oxfordian strata, it is postulated that chemoherms possibly acted as refugia for these peculiar echinoids, which have an episodic record between the Callovian and Valanginian.     

Action of the herbicides neburon and siduron on membrane permeabilities in potato tuber mitochondria

The herbicides neburon and siduron are uncouplers of oxidative phosphorylation in potato tuber (Solanum tuberosum L. cv. Bintje) mitochondria. Their effect on the ion permeabilities of the mitochondrial membrane was investigated using the acid-base pulse technique, swelling experiments and integrity tests. Both herbicides permeabilize the membrane to H⁺ ions. They have no action on the permeabilities of K⁺ and Fe(CN)^3?₆. The swelling observed with Ca²⁺ was better interpreted as an effect on membrane structure than as a true swelling. Diuron, a parent compound that does not uncouple oxidative phosphorylation, does not act on Ca²⁺-induced apparent swelling.     

Hybridization and introgression across different ploidy levels in the Neotropical orchids Epidendrum fulgens and E. puniceoluteum (Orchidaceae)

The hypothesis of gene flow between species with large differences in chromosome numbers has rarely been tested in the wild, mainly because species of different ploidy are commonly assumed to be reproductively isolated from each other because of instantaneous and strong postzygotic barriers. In this study, a broad‐scale survey of molecular variation was carried out between two orchid species with different ploidy levels: Epidendrum fulgens (2n = 2x = 24 chromosomes) and Epidendrum puniceoluteum (2n = 4x = 52 chromosomes). To test the strength of their reproductive barriers, we investigated the distribution of genetic variation in sympatric and allopatric populations of these two species and conducted crossing experiments. Nuclear and plastid microsatellite loci were used to genotype 463 individuals from eight populations across the geographical range of both species along the Brazilian coastal plain. All six sympatric populations analysed presented hybrid zones, indicating that hybridization between E. fulgens and E. puniceoluteum is a common phenomenon. Bayesian assignment analysis detected the presence of F₁ and F₂ individuals and also signs of introgression, demonstrating a high potential for interspecific gene flow. Introgression occurs preferentially from E. fulgens to E. puniceoluteum. Pure parental individuals of both species display strong genotype–habitat associations, indicating that environment‐dependent selection could be acting in all hybrid zones. This study suggests that hybridization and introgression are evolutionary processes playing a role in the diversification of Epidendrum and indicates the importance of investigations of hybrid zones in understanding reproductive barriers and speciation processes in Neotropical orchid species.     

Productivity Estimates From Upland Bird Harvests: Estimating Variance and Necessary Sample Sizes

Abstract: Harvest of upland game birds in concert with sampling of age ratios from wings can yield important biological information about populations. Although estimates of productivity are commonly produced, they are often not accompanied by a measure of variance. Thus, we developed standard error estimates for sample productivity ratios, compared 4 methods for creating confidence intervals for population productivity ratios, and developed a test and the corresponding sample size requirements for comparing 2 population productivity ratios. We applied these techniques to greater sage-grouse (Centrocercus urophasianus) wing-data collected in Oregon, USA (1993–2005). Computer simulations indicated that backtransforming the Wilson's score interval on the proportion of immatures in the sample results in the most reliable confidence intervals among the methods considered. We recommend to managers measuring conservation action outcomes with productivity ratios to consider the appropriate sample sizes for the spatial and temporal scale of their monitoring programs.