Parallel evolution of sexual isolation in sticklebacks

Mechanisms of speciation are not well understood, despite decades of study. Recent work has focused on how natural and sexual selection cause sexual isolation. Here, we investigate the roles of divergent natural and sexual selection in the evolution of sexual isolation between sympatric species of threespine sticklebacks. We test the importance of morphological and behavioral traits in conferring sexual isolation and examine to what extent these traits have diverged in parallel between multiple, independently evolved species pairs. We use the patterns of evolution in ecological and mating traits to infer the likely nature of selection on sexual isolation. Strong parallel evolution implicates ecologically based divergent natural and/or sexual selection, whereas arbitrary directionality implicates nonecological sexual selection or drift. In multiple pairs we find that sexual isolation arises in the same way: assortative mating on body size and asymmetric isolation due to male nuptial color. Body size and color have diverged in a strongly parallel manner, similar to ecological traits. The data implicate ecologically based divergent natural and sexual selection as engines of speciation in this group.

The effect of silicon content on the microstructure and creep behavior in die-cast magnesium AS alloys

The effect of increasing levels of silicon on the microstructure and creep properties of high-pressure die-cast Mg-Al-Si (AS) alloys has been investigated. The morphology of the Mg2Si phase in die-cast AS alloys was found to be a function of the silicon content. The Mg2Si particles in castings with up to 1.14 wt pct Si have a Chinese script morphology. For AS21 alloys with silicon contents greater than 1.4 wt pet Si (greater than the alpha-Mg2Si binary eutectic point), some Mg2Si particles have a coarse blocky shape. Increasing the silicon content above the eutectic level results in an increase in the number of coarse faceted Mg2Si particles in the microstructure. Creep rates at 100 hours were found to decrease with increasing silicon content in AS-type alloys. The decrease in creep rate was most dramatic for silicon contents up to 1.1 wt pct. Further additions of silicon of up to 2.64 wt pct also resulted in significant decreases in creep rate.

Effective assertive behavior in the workplace: Responding to unfair criticism

A social rules perspective was employed to identify the elements of socially appropriate responses to unfair criticism in the workplace. Women generally endorsed for themselves response strategies based on stronger obligation and softer rights components, while men endorsed responses based on stronger personal rights expression and weaker obligation components. In support of the utility of a social rules approach to operationalizing context-specific expectations, behavioral responses based on gender and status-specific rules were evaluated as more effective on task, relationship, and self-respect dimensions than were rights-only, rights-plus-empathy, or submissive strategies. Results are discussed in terms of the development of a context-specific model of interpersonal competence and implications for interpersonal skills and assertion training.

Familial influence on offspring gambling: a cognitive mechanism for transmission of gambling behavior in families

Background. The problem-gambling literature has identified a range of individual, cognitive, behavioral and emotional factors as playing important roles in the development, maintenance and treatment of problem gambling. However, familial factors have often been neglected. The current study aims to investigate the possible influence of parental factors on offspring gambling behavior. Method. A total of 189 families (546 individuals) completed several questionnaires including the South Oaks Gambling Screen (SOGS) and the Gambling Related Cognition Scale (GRCS). The relationships were examined using Pearson product-moment correlations and structural equation modeling (SEM) analyses. Results. Results showed that generally parents' (especially fathers') gambling cognitions and gambling behaviors positively correlated with offspring gambling behaviors and cognitions. However, SEM analyses showed that although parental gambling behavior was directly related to offspring gambling behavior, parental cognitions were not related to offspring gambling behavior directly but indirectly via offspring cognitions. Conclusion. The findings show that the influence of parental gambling cognition on offspring gambling behavior is indirect and via offspring cognitions. The results suggest a possible cognitive mechanism of transmission of gambling behavior in the family from one generation to the next.

Sexual abuse in childhood and sexual dysfunction in adulthood: An Australian population-based study

This study examined self-reported adult sexual functioning in individuals reporting a history of childhood sexual abuse (CSA) in a representative sample of the Australian population. A sample of 1793 persons, aged 18-59 years, were randomly selected from the electoral roll for Australian states and territories in April 2000. Respondents were interviewed about their health status and sexual experiences, including unwanted sexual experiences before the age of 16 years. More than one-third of women and approximately one-sixth of men reported a history of CSA. Women were more likely than men to report both non-penetrative and penetrative experiences of CSA. For both sexes, there was a significant association between CSA and symptoms of sexual dysfunction. In assessing the specific nature of the relationship between sexual abuse and sexual dysfunction, statistically significant associations were, in general, evident for women only. CSA was not associated with the level of physical or emotional satisfaction respondents experienced with their sexual activity. The total number of lifetime sexual partners was significantly and positively associated with CSA for females, but not for males; however, the number of sexual partners in the last year was not related to CSA. CSA in the Australian population is common and contributes to significant impairment in the sexual functioning of adults, especially women. These consequences appear not to extend to the other areas of sexual activity considered in this study.

Muscle fiber and motor unit behavior in the longest human skeletal muscle

The sartorius muscle is the longest muscle in the human body. It is strap-like, up to 600 mm in length, and contains five to seven neurovascular compartments, each with a neuromuscular endplate zone. Some of its fibers terminate intrafascicularly, whereas others may run the full length of the muscle. To assess the location and timing of activation within motor units of this long muscle, we recorded electromyographic potentials from multiple intramuscular electrodes along sartorius muscle during steady voluntary contraction and analyzed their activity with spike-triggered averaging from a needle electrode inserted near the proximal end of the muscle. Approximately 30% of sartorius motor units included muscle fibers that ran the full length of the muscle, conducting action potentials at 3.9 +/- 0.1 m/s. Most motor units were innervated within a single muscle endplate zone that was not necessarily near the midpoint of the fiber. As a consequence, action potentials reached the distal end of a unit as late as 100 ms after initiation at an endplate zone. Thus, contractile activity is not synchronized along the length of single sartorius fibers. We postulate that lateral transmission of force from fiber to endomysium and a wide distribution of motor unit endplates along the muscle are critical for the efficient transmission of force from sarcomere to tendon and for the prevention of muscle injury caused by overextension of inactive regions of muscle fibers.

Attachment insecurity as a filter in the decoding and encoding of nonverbal behavior in close relationships

In this article, I have focused my comments on the possible associations between the cognitions related to different attachment styles, and the impact that those cognitions are likely to have on nonverbal encoding and decoding. I see attachment insecurity as acting as a filter, distorting both encoding and decoding processes. In terms of decoding, an insecure individual may appraise the situation as more threatening than it actually is, may see the attachment figure as more or less available than he or she actually is, and may make an inappropriate decision about the viability or desirability of seeking proximity to the attachment figure. Attachment insecurity is also likely to inhibit the distressed individual from expressing their distress in a way that is understood by the attachment figure and that increases the likelihood that the attachment figure will engage in supportive behavior.

Diurnal polyp expansion behavior in stony corals may enhance carbon availability for symbionts photosynthesis

Photosynthesis of zooxanthellate stony corals may be limited by inorganic carbon at high irradiances. We demonstrated that oxygen consumption of expanded corals is higher than that of contracted corals in both night-expanding and day-expanding corals. It is assumed that at the single-polyp level, the expansion of tentacles increases the surface area for solute exchange with the surrounding water, which may alleviate potential carbon limitation and excess oxygen levels in the tissue under high irradiance. We investigated this hypothesis using stable carbon isotope (613 C) analysis of coral species from the Red Sea exhibiting different morphologies. delta C-13 ratios in zooxanthellae of branched coral colonies with small polyp size that extend their tentacles during daytime (diurnal morphs) showed lower delta C-13 values in their zooxanthellae - 13.83 +/- 1.45 parts per thousand, compared to corals from the same depth with large polyps, which are usually massive and expand their tentacles only at night (nocturnal morphs). Their algae delta C-13 was significantly higher, averaging - 11.33 +/- 0.59 parts per thousand. Carbon isotope budget of the coral tissue suggests that branched corals are more autotrophic, i.e., that they depend on their symbionts for nutrition compared to massive species, which are more heterotrophic and depend on plankton predation. (c) 2005 Elsevier B.V. All rights reserved.