Restriction fragment length polymorphisms of horse class II MHC genes observed using various human alpha-and beta-chain cDNA probes

Genomic DNA isolated from 20 horses was digested with up to six restriction endonucleases and subjected to southern blot hybridization analysis using various human class II alpha- and beta-chain cDNA probes. A high degree of restriction fragment length polymorphism (RFLP) was found for the DQ alpha, DP beta, DQ beta and DR beta probes, about 20 polymorphic bands being detected for each. DR alpha showed 2-4 polymorphic bands, whereas no evidence for DP alpha-like genes was found. A number of correlations of RFLPs with individual alloantisera were apparent.     

Distinguishing Drift and Selection Empirically: “The Great Snail Debate” of the 1950s

Biologists and philosophers have been extremely pessimistic about the possibility of demonstrating random drift in nature, particularly when it comes to distinguishing random drift from natural selection. However, examination of a historical case – Maxime Lamotte’s study of natural populations of the land snail, Cepaea nemoralis in the 1950s – shows that while some pessimism is warranted, it has been overstated. Indeed, by describing a unique signature for drift and showing that this signature obtained in the populations under study, Lamotte was able to make a good case for a significant role for␣drift. It may be difficult to disentangle the causes of drift and selection acting in a population, but it is not (always) impossible.     

The reactivity of neonatal rabbits to the mammary pheromone as a probe for viability

Newborn rabbits depend on a daily nursing interaction with the mother to gain milk and to survive. During this interaction, they localise and seize the nipples displaying a typical behaviour triggered by maternal odour cues. The mammary pheromone constitutes such a signal in domestic rabbits: it elicits sucking-related movements in more than 90% of the pups. However, some newborns remain unresponsive to the presentation of the pheromone, even pups apparently healthy and highly motivated to suck. The main goal of the present study was therefore to explore the link between the unresponsiveness of rabbit pups to the mammary pheromone and their growth and survival in breeding conditions. To that end, 293 newborns from 30 litters were tested for their head searching-oral grasping responses to the mammary pheromone on days 1 and 3, and their milk intake and mortality were followed up from days 1 to 21. It was hypothesised that unresponsive newborns would have subsequent difficulties in finding nipples, sucking and surviving. Early weight and success in milk intake were further considered as mediating factors in growth and viability. The results showed that pups that were unresponsive to the mammary pheromone on day 1 were less successful in gaining milk and had a higher rate of mortality than the responsive pups. However, this impact was modulated by the weight of pups: it appeared only in the lightest newborns. Moreover, this impact vanished on day 3. On the other hand, the pup weight and sucking success on days 1 to 3 strongly influenced viability and growth during the period extending from days 1 to 21. Taken together, the results show that the day-1 responsiveness of rabbit pups to the mammary pheromone can be considered as an indicator of individual viability in pups having a small weight (<48 g on day 1). The predictive validity of the pups’ pheromonal reactivity seems however time-limited as it works only during the first, but crucial, postnatal days.     

Microsatellites from the vairone Leuciscus souffia (Pisces: Cyprinidae) and their application to closely related species

Eleven microsatellites were isolated from the vairone Leuciscus souffia (Risso 1826), an endangered fish that inhabits river systems in and around the Alps in Europe. The level of genetic diversity was assessed in 29 individuals of the subspecies L. s. souffia, and their variability was further estimated in seven individuals of a different subspecies, L. s. muticellus. Eight of these microsatellite loci were also applied to seven closely related cyprinid species. Availability of the reported microsatellite loci will facilitate the investigation of population genetic structure of these species with applications for the development of conservation strategies and phylogeographical approaches.     

Epilogue — Demography and anthropology

As a conclusion, this paper reviews briefly the content of the volume. The wealth of demographic data has not been adequately exploited in anthropology; this is why this publication is valuable in showing attempts to apply demographic data in a variety of anthropological problems. This symposium has explored many interesting points which we recall here. Yet it has also opened up a whole range of further questions on the material presented as well as in this broad field. Several directions of research could be developed, for instance, testing among human populations, over long periods, the ecological thoughts of ecosystems evolving as a cascade of instabilities, rather than a succession of equilibrium states. Let us also recall the pervasive nature of demographic facts in topics such as the energy cycle or the genetic structure and evolution of human populations.     

Function and genetics of long versus short copulations in the cactophilic fruit fly,drosophila mojavensis (diptera: drosophilidae)

Variation in copulation duration of Drosophila mojavensisstrains was influenced by both sexes. Males maintained predominant control, as copulation duration of pairs from different strains was more similar to that of the strain from which the male was derived, but female origin also contributed significantly to the duration of copulation. Variation among strains was controlled by genes acting additively in both sexes. The size of both males and females also affected copulation duration. Small males copulated longer on average than large males, while males paired with large females copulated longer than those paired with small females. The importance of copulation duration to fitness was tested by correlation analyses with male size, female size, female remating latency, and number of eggs laid prior to female remating. Longer copulations stimulated earlier oviposition, possibly by increasing accessory gland secretions that are passed by males during copulation.     

Genetic structure of a wide-spectrum chicken gene pool

The genetic structure of 65 chicken populations was studied using 29 simple sequence repeat loci. Six main clusters which corresponded to geographical origins and histories were identified: Brown Egg Layers; predominantly Broilers; native Chinese breeds or breeds with recent Asian origin; predominantly breeds of European derivation; a small cluster containing populations with no common history and populations that had breeding history with White Leghorn. Another group of populations that shared their genome with several clusters was defined as 'Multi-clusters'. Gallus gallus gallus (Multi-clusters), one of the subspecies of the Red Jungle Fowl, which was previously suggested to be one of the ancestors of the domesticated chicken, has almost no shared loci with European and White Egg layer populations. In a further sub-clustering of the populations, discrimination between all the 65 populations was possible, and relationships between each were suggested. The genetic variation between populations was found to account for about 34% of the total genetic variation, 11% of the variation being between clusters and 23% being between populations within clusters. The suggested clusters may assist in future studies of genetic aspects of the chicken gene pool.     

Frequency-dependent conspecific attraction to food patches

In many ecological situations, resources are difficult to find but become more apparent to nearby searchers after one of their numbers discovers and begins to exploit them. If the discoverer cannot monopolize the resources, then others may benefit from joining the discoverer and sharing their discovery. Existing theories for this type of conspecific attraction have often used very simple rules for how the decision to join a discovered resource patch should be influenced by the number of individuals already exploiting that patch. We use a mechanistic, spatially explicit model to demonstrate that individuals should not necessarily simply join patches more often as the number of individuals exploiting the patch increases, because those patches are likely to be exhausted soon or joining them will intensify future local competition. Furthermore, we show that this decision should be sensitive to the nature of the resource patches, with individuals being more responsive to discoveries in general and more tolerant of larger numbers of existing exploiters on a patch when patches are resource-rich and challenging to locate alone. As such, we argue that this greater focus on underlying joining mechanisms suggests that conspecific attraction is a more sophisticated and flexible tactic than currently appreciated.