Biosynthetic and metabolic activities of some organelles in Papaver somniferum latex

The biosynthesis of the five major alkaloids of the opium poppy (Papaver somniferum L. from radioactive dihydroxyphenylalanine has been studied in the 1000 g, 10 000 g, 100 000 g pellets and the 100 000 g supernatant fractions of the capsule latex. A normal poppy variety as well as one which produces only traces of alkaloids were used. Definite evidence of biosynthesis was obtained for both varieties but only in the 1 000 g pellet (as previously reported . None was found in the other fractions although electron microscopy showed that organelles, including vesicles, were present. The amounts of alkaloid biosynthesized however were very small relative to the amounts involved in the rapid changes already reported for the developing capsules. In contrast, all fractions of the latex were able to metabolize T-morphine in vitro, with the 100 000 g supernatant showing the highest activity and the amounts involved were also consistent with the changes found in the living plant.     

Dispersal of deer mice,Peromyscus maniculatus

Summary Dispersal of deer mice, Peromyscus maniculatus, was measured as immigration to and emigration from two control areas, and as immigration to a removal area. The number of mice dispersing was linearly related to the densities on the control areas, while the proportion of the population dispersing (rate of dispersal) was correlated primarily with the rate of increase of control populations. High rates of dispersal were also associated with a breakdown of the established social structure in the spring and fall. Dispersing animals were compared to residents with respect to sex ratio, weight, age, and breeding condition. The types of animals dispersing varied seasonally: light-weight, non-breeding males dispersed in the spring and summer; juveniles and breeding males dispersed at the end of the breeding season; and light-weight mice of both sexes dispersed over the winter. It is proposed that the animals that dominated the dispersal samples each season were moving in response to social pressure from residents, or local limitations of some resource, and thus, that dispersal was adaptive for the individuals concerned. Some tests of the hypotheses concerning resource limitation are suggested.     

Selection on male size,leg length and condition during mate search in a sexually highly dimorphic orb-weaving spider

Mate search plays a central role in hypotheses for the adaptive significance of extreme female-biased sexual size dimorphism (SSD) in animals. Spiders (Araneae) are the only free-living terrestrial taxon where extreme SSD is common. The gravity hypothesis states that small body size in males is favoured during mate search in species where males have to climb to reach females, because body length is inversely proportional to achievable speed on vertical structures. However, locomotive performance of males may also depend on relative leg length. Here we examine selection on male body size and leg length during mate search in the highly dimorphic orb-weaving spider Argiope aurantia, using a multivariate approach to distinguish selection targeted at different components of size. Further, we investigate the scaling relationships between male size and energy reserves, and the differential loss of reserves. Adult males do not feed while roving, and a size-dependent differential energy storage capacity may thus affect male performance during mate search. Contrary to predictions, large body size was favoured in one of two populations, and this was due to selection for longer legs. Male size was not under selection in the second population, but we detected direct selection for longer third legs. Males lost energy reserves during mate search, but this was independent of male size and storage capacity scaled isometrically with size. Thus, mate search is unlikely to lead to selection for small male size, but the hypothesis that relatively longer legs in male spiders reflect a search-adapted morphology is supported.     

The sexual arms race and phenotypic correlates of mating success in the waterstrider,Aquarius remigis (Hemiptera: Gerridae)

Intersexual conflicts over mating decisions may have an important impact on the evolution of mating behaviours and strategies and may develop into an arms race between the sexes. In waterstrider species, where intersexual conflict is known to occur, the evolution of male traits that allow them to overcome female reluctance to mate is expected. Reproductively active waterstriders,Aquarius remigis, were videotaped in the laboratory to examine the influence of total body length and front femoral width of males, male: female body size ratio, and female reproductive condition (number of mature eggs) on three variables associated with mating success: duration of the premating struggle, duration of mating, and number of successful matings. None of these behaviors was significantly correlated with the size ratio of the mating pair. However, total body length was negatively correlated with premating struggle duration, male front femoral width was positively correlated with number of successful matings, and number of mature eggs in females was positively correlated with duration of both the premating struggle and the mating itself. The relative influence of male sexual armaments and female choice on the outcome of mating interactions is discussed.