Sexual behaviour in castrated rabbits treated with varying doses of testosterone

Sexual behaviour was studied in castrated rabbits injected every third day with 1, 7·5, 15 or 30 mg TP, during a 120-day period. Castration led to a very pronounced reduction of sexual activity. This was restored to precastration levels by the three larger doses used about 60 days after the beginning of hormone treatment. The lowest dose did not cause any significant increase in sexual activity. About 70 days after the hormone treatment ceased, almost all sexual activity had disappeared. The correlation coefficients obtained between the various parameters of sexual activity ranged between 0·21 and 0·54. The present observations are discussed in relation to results obtained with other species.     

Über die Keimungsverhältnisse und Auswuchsneigung rot- und weißkörniger Weizensorten

Ohne Zusammenfassung     

Chromosomal localization of three human genes encoding bone morphogenetic protein receptors

Bone morphogenetic proteins (BMPs) are members of the TGF-β superfamily that play a pivotal role in bone formation during embryogenesis and fracture repair. BMP signaling occurs via hetero-oligomeric serine/threonine kinase complexes of BMP type I (BMPR-IA or BMPR-IB) and type II receptors (BMPR-II). BMPR-IA and IB are closely related receptors, with sequence differences conserved between different species, suggesting that they serve distinct functions. Here we report the cDNA cloning of human BMPR1B and the chromosomal localization of all three BMPR genes. Using somatic cell hybrid and FISH analyses, the BMPR1A, BMPR1B, and BMPR2 genes were assigned to 10q23, 4q22-24, and 2q33-34, respectively. A processed BMPR1A pseudogene was mapped to 6q23. Received: 17 February 1997 / Accepted: 15 October 1998     

Ragweed – An allergy risk in Sweden?

Ragweed pollen, which is a major cause of allergic rhinitis in North America and during the last decades, also in parts of the European continent, has not been regarded as a risk in Sweden, since occurrences of Ambrosia have been rare and with two exceptions, ephemeral. During the last four years, however, long-distance transported pollen has been registered in South Sweden. Moreover, seeds are dispersed by man with birdseed and reports on ragweed plants growing at birdtables are becoming more and more common. In warm years, the fruits of these plants mature and are germinative. We argue that there is a risk that ragweed pollen may be a problem in the future in Sweden. Long-distance transport from the continent is likely to be increasingly more common, and in larger amounts, as ragweed is rapidly spreading in Europe. Among the plants now appearing within Sweden, selection is likely to favour phenotypes which are able to fulfil their life-cycle during the indigenous vegetation period, especially in a scenario of global warming.     

Greenbeards in yeast: an undergraduate laboratory exercise to teach the genetics of cooperation

Recent years have seen a dramatic increase in our understanding of the social behaviour of microbes. Here, we take advantage of these developments to present an undergraduate laboratory exercise that uses the cooperative flocculating behaviour of yeast (Saccharomyces sp.) to introduce the concept of inclusive fitness and teach the genetics of cooperation. Students generate their own data using co-cultures of various yeast strains and perform statistical analyses to test whether kin selection or greenbeard effects determine the cooperative flocculating behaviour. The lab has run successfully for two consecutive years in a second year course with some 1, 200 students per year at the University of Toronto, Canada. We discuss the benefits of using microbes to teach social evolution, describe the set-up and learning outcomes of the laboratory exercise, and then outline possible extension and variants of the lab. In addition to providing students with the opportunity to use a model organism to study social behaviour, students are also taught common laboratory skills, such as replica plating and sterile techniques. Ultimately, while the genetics of cooperation has traditionally been taught through computer simulations and evolutionary games, this exercise demonstrates a way to experimentally introduce the topic.     

Evolution of the selfing syndrome: Anther orientation and herkogamy together determine reproductive assurance in a self‐compatible plant

Capacity for autonomous self‐fertilization provides reproductive assurance, has evolved repeatedly in the plant kingdom, and typically involves several changes in flower morphology and development (the selfing syndrome). Yet, the relative importance of different traits and trait combinations for efficient selfing and reproductive success in pollinator‐poor environments is poorly known. In a series of experiments, we tested the importance of anther–stigma distance and the less studied trait anther orientation for efficiency of selfing in the perennial herb Arabis alpina. Variation in flower morphology among eight self‐compatible European populations was correlated with efficiency of self‐pollination and with pollen limitation in a common‐garden experiment. To examine whether anther–stigma distance and anther orientation are subject to directional and/or correlational selection, and whether this is because these traits affect pollination success, we planted a segregating F2 population at two native field sites. Selection strongly favored a combination of introrse anthers and reduced anther–stigma distance at a site where pollinator activity was low, and supplemental hand‐pollination demonstrated that this was largely because of their effect on securing self‐pollination. The results suggest that concurrent shifts in more than one trait can be crucial for the evolution of efficient self‐pollination and reproductive assurance in pollinator‐poor habitats.     

Winter sheltering by juvenile brown trout (Salmo trutta) – effects of stream wood and an instream ectothermic predator

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Microclimatic buffering by logging residues and forest edges reduces clear‐cutting impacts on forest bryophytes

Question: The practice of extracting logging residues after clear‐cutting for bioenergy purposes is spreading. Logging residues constitute a shelter in clear‐cut areas and therefore concerns have been expressed that their removal could make the ground and its vegetation more exposed to extreme microclimatic conditions. We asked whether logging residues and forest edges can protect ground‐dwelling forest bryophytes from fatal microclimate events following clear‐cutting. Location: Boreal forests of central Sweden. Methods: Using transplants of eight forest floor bryophyte species we experimentally analysed the sheltering effect (less solar radiation and less wind) of logging residues and forest edges in seven clear‐cut areas. Transplants were placed in two contrasting positions in each area; near a north‐facing forest edge and in the centre of the clear‐cut area. In each position, half of the transplants were covered by a layer of spruce branches and the other half was left uncovered. We estimated proportion of apparently living shoots (apparent vitality) and measured radial growth of transplants during one growing season. Results: Position in the clear‐cut area, but not cover of spruce branches, clearly influenced radial growth. Vitality scores were higher among transplants covered with branches and the lowest apparent vitality was observed in uncovered transplants in the middle of clear‐cut areas. The change in area of apparently living shoots during the course of the experiment (growth minus mortality) was unaffected by branch cover close to the edge but positively affected in the centre of the clear‐cut area. In general, the effect of branch cover on bryophytes was higher in the centre of clear‐cut areas. Here, climatic measurements showed that branch cover buffers during periods of extreme microclimates. Conclusions: Extraction of logging residues after clear‐felling may reduce the survival of some ground‐dwelling forest organisms. The additional sheltering provided by branches was unimportant close to forest edges. We suggest smaller clear‐cut areas, green‐tree retention and other ways to make logged areas shadier and less windy to mitigate the reduced shelter caused by harvest of logging residues.