Abstract Cases of interest using affected sib‐pair methods to distinguish between recessive and additive (dominant) modes of inheritance of a disease‐predisposing gene involve goodness‐of‐fit tests with a small expected number in the “share‐zero parental haplotypes” category, as well as an unknown parameter, the frequency of the disease‐predisposing allele. Our simulations demonstrate that the real significance level of the chi‐square test using the three‐haplotype‐sharing IBD values (share 2, 1, and 0 parental haplotypes) is close to the assumed (.05) level in these cases, so that the haplotype‐sharing classes do not have to be lumped, which would leave no degrees of freedom for a statistical test. The validity of the chi‐square approximation in cases of small expected freqencies has previously been described, but the situations that have been considered do not cover the very small values in the share‐zero category that are often expected in the affected sib‐pair analysis, nor do they involve estimation of an unknown parameter. Although including IBD values from affected kin pairs other than sibs can be a very powerful tool in demonstrating linkage of a marker and disease, these pairs do not add power, in fact they reduce the power, of the chi‐square tests of goodness‐of‐fit of modes of inheritance.
Laboratory-reared bumblebees were allowed to forage on 30 artificial flowers which were identical in morphology and reward schedule, but were marked by either a human-blue, a human-green, or a human-white landing surface. The probability of nectar rewards in the artificial flowers, and their spatial distribution, were manipulated experimentally. The bees' color choices in the different experimental treatments were compared. The proportions of visits to the three colors deviated significantly from the expected random choice (1/3,1/3,1/3) for more than 50% of the bees. Of these bees, 38%, 32%, and 30% formed a preference for human-blue, human-green, and human-white, respectively. The frequency of nonrandom color choice, and the strength of the deviation from random choice, were highest when the different colors were placed in separate clusters, lower when they were placed in adjacent clusters, and lowest when they were randomly intermingled. Nonrandom color choice was also more pronounced when the bees were rewarded according to a constant schedule, rather than probabilistically. A statistically significant preference for human-blue was found during the bees' first three visits. The bees' tendency for “runs” of consecutive visits to the same flower color can partially account for their non- random color choices. Effects of innate preferences, early learning, generalization, and search-image formation on color choice are discussed.
Abstract The distribution of the intertidal barnacle Chthamalus montagui spans the West Mediterranean Sea and the Northeast Atlantic shores of Europe and West Africa. Knowledge of the phylogeography of this species has been limited to the Mediterranean and the European shores of the Atlantic. The present study considers the populations of West Europe, but also focuses on the overlooked populations of West Africa. We performed a molecular analysis using two markers: the mitochondrial COI gene and the nuclear rRNA ITS gene. Whereas ITS proved to be non‐informative, COI has demonstrated that the East Atlantic population of C. montagui comprises two genetically distinct clades: a northern clade that ranges from Mauritania to Scotland and a southern clade that comprises the populations from Senegal. These clades are separated by the Cape Verde Front, which stretches west of the upwelling area off Mauritania. We consider these clades as two cryptic species of the nominal species C. montagui .
We show in this study that the population of Chthamalus dentatus along the Atlantic coast of Africa displays a genetic division into four clades, namely: the South African, the Namibian-Angolan, the Cameroonian and the West African clade. This division is based on four genes – two mitochondrial genes, cytochrome c oxidase subunit I (COI) and the control region (D-loop), with the addition of two nuclear genes, the elongation factor (EF1) and the sodium-potassium ATPase (NaKA). The unique morphological feature of C. dentatus – dentated sutures between the shell compartments – is apparent in the specimens of the four clades, thus we define these clades as cryptic species of C. dentatus. The present work extends previous studies on the population genetics of C. dentatus that were based on COI only, by adding more genes and expanding the range of collection sites. In addition, the availability of new specimens from West Africa also enabled us to increase the northern limit of this species' range to include Northern Senegal.
The star barnacle, Chthamalus stellatus Poli, populates the Mediterranean Sea, the North-Eastern Atlantic coasts, and the offshore Eastern Atlantic islands. Previous studies have found apparent genetic differences between the Atlantic and the Mediterranean populations of C. stellatus, suggesting possible geological and oceanographic explanations for these differences. We have studied the genetic diversity of 14 populations spanning from the Eastern Atlantic to the Eastern Mediterranean, using 63 genomic polymorphic sites. We have found that these populations form four distinct clusters: Eastern Atlantic, Western Mediterranean, Mid-Mediterranean and Eastern Mediterranean, with evident connectivity between them. We examined here environmental conditions like surface currents, water salinity and temperature as probable factors that have formed the population structure. We suggest that C. stellatus is a suitable marine animal for studying how geological events and hydrographic conditions shape the fauna in the Mediterranean Sea.
Abstract In this study troop of chacma baboons (Papio cynocephalus ursinus) at Mkuzi Game Reserve, Zululand, South-Africa, it is suggested that risk of predation and competition over safe spatial position had more importance and effect on female behaviour than did competition for food. Only 6.4% of all agonistic events were over food patches and no significant correlation was found between a female's dominance rank and proportion of time spent feeding, feeding bout length or diet composition. Parameters of reproductive success, such as inter-birth intervals and infant mortality were not correlated with female dominance rank. Female mortality, however, was related to dominance rank and all of the five females who disappeared during the study were low-ranking. Four of the five females disappeared after troop fission. There is circumstantial evidence supporting the suggestion that predation by leopards is the main cause of mortality of females at Mkuzi. High levels of female aggression were recorded, with almost no occurrences of support coalitions. Most of the aggression took place among similar ranking females, or was directed by the top ranking toward the lowest ranking females. Most of the female-to-female agonistic encounters were in a social context, and more than half were over a spatial position next to other adult troop members. Aggression among females increased after troop fission. It is suggested that the higher-ranking females may be better protected from predation, through access to more central spatial positions in the troop. Indeed, a positive correlation was found between a female's dominance rank and the time spent next to other adult troop members. It may be that avoiding food competition by keeping larger distances from others, while foraging, was translated in lower ranking females to a cost of higher predation risk.
