Pheromone-mediated sexual selection in the mothUtetheisa ornatrix: Olfactory receptor neurons responsive to a male-produced pheromone

Male Utetheisa ornatrixhave a pair of eversible glandular brushes (coremata) which are displayed during precopulatory interactions with the female. Earlier studies have shown that a pheromone associated with the coremata, hydroxydanaidal (HD), is derived by the males from pyrrolizidine alkaloids (PAs) that they sequester as larvae from their foodplants (Crotalariaspp.) The PAs impart a distastefulness upon Utetheisathat protects both larvae and adults against predation. The receptor neurons specialized for detection of HD are housed in sensilla whose morphological features, as revealed by scanning electron microscopy, classify them as sensilla basiconica. The sensitivity and dynamic range of these receptor neurons were largely unaffected by whether the females were raised on an alkaloid-free diet or on a diet supplemented with Crotalariaseeds. Acetylation of the hydroxyl group of HD substantially reduced the activity of the molecule. None of the antennal sensilla examined contained receptor neurons sensitive to a PA (monocrotaline) or its N-oxide.     

Is male back space limiting? An investigation into the reproductive demography of the giant water bug,Abedus indentatus (Heteroptera: Belostomatidae)

Because male giant water bugs in the subfamily Belostomatinae provide parental care by brooding eggs on their back, an accurate assessment can be made of both the actual and potential reproductive capacity of males. Two operational sex-ratio (OSR) indices were developed and empirically measured for a population of giant water bug, Abedus indentatus,in California. One index was based on reproductive rates measured in the laboratory; the other index was based on reproductive resources observed in the field. Both OSR indices suggest that the operational sex ratio fluctuates between maleskewed ratios in the summer and femaleskewed ratios in the winter. This pattern appears to be the consequence of two factors. First, the adult sex ratio is significantly female biased. Second, although males can outreproduce females at high ambient temperatures, the reverse is true at low temperatures. Possible reasons for the female-skewed adult sex ratio are examined, including differential recruitment, differential mortality, and sampling bias.     

A maximum likelihood approach to the detection of selection from a phylogeny

Summary A large amount of information is contained within the phylogentic relationships between species. In addition to their branching patterns it is also possible to examine other aspects of the biology of the species. The influence that deleterious selection might have is determined here. The likelihood of different phylogenies in the presence of selection is explored to determine the properties of such a likelihood surface. The calculation of likelihoods for a phylogeny in the presence and absence of selection, permits the application of a likelihood ratio test to search for selection. It is shown that even a single selected site can have a strong effect on the likelihood. The method is illustrated with an example fromDrosophila melanogaster and suggests that delerious selection may be acting on transposable elements.     

Vocal morphology of the Physalaemus pustulosus species group (Leptodactylidae): morphological response to sexual selection for complex calls

Most male frogs in the genus Physalaemus produce a whine-like advertisement call. Male P. pustulosus , however, add chucks to the call. This enhances the attractiveness of the call to females, and has evolved under the influence of sexual selection despite the increased predation risk from the frog-eating bat ( Trachops cirrhosus ). This complex call is unusual, if not unique, among anurans because the two call components overlap in time. Here we investigate the morphological changes responsible for the production of complex calls.
The Physalaemus purtulosus species group consists of four species. Physalaemus pustulosus and P. petersi are sister species, and recently it has been shown that P. petersi produces chucks. Physalaemus coloradorum and P. purtulatus are sister species and neither is known to produce chucks. Two laryngeal characters vary within the species group. Physalaemus pustulosus has a large fibrous mass (FMI), whose vibration is responsible for production of the chuck. This mass is much smaller in the other three species. In P. pustulosus and P. petersi the FMI is anchored dorsally, deep within the bronchial process, the attachment is more extensive in P. pustulosus. Neither P. pustulatus nor P. coloradorum have such a dorsal attachment associated with their FMI. This character is responsible for allowing the FMI to vibrate independently of the vocal cords, that is, for the production of the complex call. Thus the morphological changes responsible for the evolution of this unusual behavioural innovation, the complex call, are gradual, and almost trival, in nature. This study also shows that the primitive condition of the larynx of the P. pustulosus and P. petersi ancestor, was predisposed to the production of complex calls.
We also document ontogenetic and sexually dimorphic patterns in larynx structure.     

Gene-directed mutagenesis on the chromosome of Bacillus subtilis 168

Summary We have devised a method whereby any mutagenized cloned DNA from Bacillus subtilis can be reinserted at the original site on the B. subtilis chromosome. The procedure depends on the accuracy and high frequency of homologous recombination between the B. subtilis chromosome and the DNA taken up by the cell. The method makes use of two drug resistance selection markers (the chloramphenicol resistance gene and the neomycin resistance gene) and a marker gene which functions as a catalyst. The utility of the method has been demonstrated using leuB and pro of B. subtilis as target gene and catalyst, respectively, and mutations such as leuB: : cat, leuB ^–, and pro: : neo constructed in vitro on the cloned DNA fragments. Transformation in sequential steps as (leuB ⁺ pro⁺)(leuB: : cat pro ⁺) (leuB ^– pro: : neo)(leuB ^– pro ⁺) resulted in a leuB ^– single mutant without affecting other regions of the B. subtilis chromosome (gene-directed mutagenesis). We also demonstrate that other single mutations such as metD ^– and pro ^–, as well as the double mutation leuB ^– pro ^– can be introduced by the same procedure. In principle, true isogenies with multiple mutations can be constructed by the method described in this paper. Furthermore, the procedure should be generally applicable to any organisms in which homologous recombination is proficient.     

The induction of lincomycin resistance in Lycopersicon peruvianum and Lycopersicon esculentum

Lincomycin-resistant calli were induced from both Lycopersicon esculentum and Lycopersicon peruvianum using N-mitroso-N-methylurea (NMU) mutagenesis. From these calli lincomycin-resistant plants were regenerated. For L. peruvianum it was shown that the resistant plants could be divided in two classes with respect to their resistance to lincomycin and its derivative clindamycin. The first class comprised plants which were resistant to 500 mg/l lincomycin and showed no shoot or root formation in the presence of clindamycin; the second class consisted of plants resistant to 2000 mg/l lincomycin and these plants were able to form shoots and roots on clindamycin containing media. Lincomycin is an inhibitor of peptidyltransferase; chloroplast encoded parts of this enzymatic function are sensitive for this antibiotic. Reciprocal crosses between our lincomycin resistant and wild type L. peruvianum plants indicated a maternal inheritance of the mutation.     

Evolutionary explanations of emotions

Emotions can be explained as specialized states, shaped by natural selection, that increase fitness in specific situations. The physiological, psychological, and behavioral characteristics of a specific emotion can be analyzed as possible design features that increase the ability to cope with the threats and opportunities present in the corresponding situation. This approach to understanding the evolutionary functions of emotions is illustrated by the correspondence between (a) the subtypes of fear and the different kinds of threat; (b) the attributes of happiness and sadness and the changes that would be advantageous in propitious and unpropitious situations; and (c) the social emotions and the adaptive challenges of reciprocity relationships. In addition to addressing a core theoretical problem shared by evolutionary and cognitive psychology, explicit formulations of the evolutionary functions of specific emotions are of practical importance for understanding and treating emotional disorders.     

How feeding performance and energy intake change with a small increase in the body size of the three-spined stickleback

Changes in the foraging behaviour due to variation in the body size of the three-spined stickleback Gasterosteus aculeatus were investigated. All sizes of fish had a high probability of attacking prey whenever encountered. The probability of eating the prey increased with the size of the fish, as the larger fish had larger jaws and a greater stomach capacity. Therefore, as fish increased in size there was an increase in the probability of successful prey capture. The level of satiation did not have an effect on the prey handling time, which is contrary to other studies and is probably a result of the large prey sizes. The physical size of the prey meant that the handling times were long regardless of the motivational level of the fish. The larger fish took in more energy and at a faster rate, although the time to reach satiation was similar for all fish sizes. The advantage that large fish appear to have in successfully gaining large prey is negated by their greater metabolic requirement. The changes in feeding performance induced by small increases in body size could have important consequences for intraspecific competition, habitat Use and risk of predation.     

Reductions in genetic variation inDrosophila andE. coli caused by selection at linked sites

Selection at linked sites has important consequences for the properties of neutral variation and for tests of the predictions of the neutral theory of molecular evolution. We review the theory of the effect of adaptive gene substitutions on neutral variability at linked sites (hitchhiking or selective sweeps) and discuss theoretical results on the effect of selection against deleterious alleles on variation at linked sites (background selection). InDrosophila melanogaster there is a clear relation between the frequency of recombination in a given region of the chromosome and the amount of natural variability in that region. Attempts to predict this relation have given rise to models of selective sweeps and background selection. We describe possible methods of discriminating between these models, and also discuss the probable strong influence of selective sweeps on variation in largely nonrecombining genomes, with particular reference toEscherichia coll. Finally we present some unresolved questions and possible directions for future research.     

Low synonymous site variation at thelacY locus inEscherichia coli suggests the action of positive selection

We have determined the nucleotide sequences of sevenlacY alleles isolated from natural isolates ofEscherichia coli. Nucleotide heterozygosity estimates for this locus were compared to those obtained from previous studies of intraspecific variation at chromosomal loci, revealing thatlacY has unusually low synonymous site variation. The average pairwise heterozygosity of synonymous sites (Ks=0.0112+/-0.0100) is the second lowest reported and the lowest for loci that have an equivalent level of nonsynonymous variation. We consider several hypotheses to explain how different forces in evolution could act to create the observed pattern of polymorphism, including selection for translational efficiency and positive selection. Our analysis most strongly supports the hypothesis that positive selection has acted on thelacY locus inE. coli.