No abstract

Gene arrangement frequencies were determined at two stages in the life history of Drosophila pseudoobscura taken from nature. Three po ulations in the central highlands of Mexico were each sampled twice during 1976.Gene arrangement frequencies were measured in adult males and in larvae that were the offspring of females collected at the same time. The adult males were in all likelihood a representative sample of those who fathered the larvae produced by the wild females. Differences in gene arrangement frequency between these two life stages should indicate the operation of natural selection. One-third of our comparisons of common gene arrangement frequencies in males and in larvae from the next generation were statistically significant, as were one-third of our comparisons of total frequency arrays in the two life stages. We consider the components of selection that could produce such frequency changes and reason that male mating success must be the major one. Gene arrangement frequencies in the Mexican populations fluctuate within wide bounds. Selection must act to retain the polymorphism in the face of this flux in gene arrangement frequencies, and we suggest that male mating success plays an important role. One of the early triumphs of ecological genetics was the demonstration that selection in nature could be intense-in fact, one or several orders of magnitude more powerful than the founders of population genetics imagined. No experimental system played a more important role in the analysis of selection than the chromosomal polymorphism for gene arrangements in Drosophila pseudoobscura. In this species a series of inversions on the third chromosome binds large blocks of genes together as units, just as though they were alleles of a single "supergene." Natural selection was first implicated when Dobzhansky (2) showed that the frequencies of certain gene arrangements went through seasonal cycles in two of three populations on Mt. San Jacinto in California; subsequent studies showed that these cycles were repeated in years scattered over a span of 2 decades (3, 4). The frequencies of gene arrangements in the third population on Mt. San Jacinto did not cycle, but between 1939 and 1946 they underwent a directional change that Dobzhansky (5) also ascribed to natural selection. Dobzhansky and Levene (6) then showed that karyotypic frequencies in eggs laid by wild females were generally in accord with Hardy-Weinberg expectations, but that frequencies in wild males were not. They concluded that the karyotypes suffered differential mortality during the transition from fertilized egg to adult fly. That selection on the D. pseudoobscura inversions occurred in nature seemed to be settled, and it was generally taken for granted that viability differences accounted for the major part of it.Some 20 years later, a series of papers by Prout (7-10) stimulated evolutionary biologists to pay greater attention to the various components to fitness. These components determine the separate bits of selection that operate at...

The reproductive capacity of a species is one of its most important attributes, intimately related to its ability to persist in a sometimes harsh environment.Reproductive capacity is a particularly good index of fitness in organisms such as many insects that go through repeated cycles of rapid population growth. In such organisms any feature of the reproductive biology that increases reproductive rate will be favored by natural selection. Repeated mating and sperm storage are specific features which can play important roles in determining female fecundity and male mating success, and hence fitness.Both females and males of many animal species mate repeatedly, and in a sizable fraction of these species the females store sperm. Insects in particular may store sperm for periods of time approaching the lifetime of an adult female. Parker (1970) reviewed the extensive literature on repeated mating and sperm storage in insects. He concluded that these processes are adaptive and the products of a kind of selection he termed sperm competition. The existence of these phenomena in a variety of species, including dragonflies, beetles, bugs, and dipteran flies, makes them of general interest to population biologists. The same processes of repeated mating, sperm storage, and the resultant selection undoubtedly operate in other arthropods and in other phyla. Our own attention has been focused on these processes in Drosophila flies.That female Drosophila store sperm from a mating has been known a long time.Likewise, it has been common knowledge that females in the laboratory will accept additional mates, sometimes long before the sperm from the first mating are exhausted (Lefevre and Jonsson 1962). An up-to-date review of sperm transfer, sperm storage, and sperm utilization in Drosophila may be found in Fowler (1973).Multiple insemination was shown to be rather common in laboratory populations of D. pseudoobscura (Dobzhansky and Pavlovsky 1967) and D. melanogaster

Eastern lowland gorillas (Gorilla gorilla graueri) are the least studied of the three gorilla subspecies; particularly at the molecular level. We sequenced an internal region of the mitochondrial DNA cytochrome oxidase subunit II (COII) region and a hypervariable portion of the mitochondrial DNA control region (D-loop) from wild gorillas in both the montane and lowland habitats of Kahuzl-Blega National Park, Democratic Republic of Congo. All individuals (n = 38) were identical at the COII region; this sequence indicates that diagnostic sites previously suggested for gorilla subspecies may be valid. Low variability was found within the D-loop region from a subset of the individuals (n = 15) sequenced for COII. Haplotype frequencies differed between the two habitats, suggesting a level of population subdivision that may have demographic consequences. These results also support the distinction of two distinct clades of gorillas comprised of western populations (G. g. gorilla) and eastern populations (G. g. graueri and G. g. beringei). Future management of Kahuzi-Biega National Park should ensure that sufficient habitat remains to prevent further genetic isolation of gorillas in the montane section of the park.

HED is an autosomal dominant skin disorder that is particularly common in the French Canadian population of south-west Quebec. We previously mapped the HED gene to the pericentromeric region of chromosome 13q using linkage analysis in eight French Canadian families. In this study, we extend our genetic analysis to include a multiethnic group of 29 families with 10 polymorphic markers spanning 5.1 cM in the candidate region. Two-point linkage analysis strongly suggests absence of genetic heterogeneity in HED in four families of French, Spanish, African and Malaysian origins. Multipoint linkage analysis in all 29 families generated a peak lod score of 53.5 at D13S1835 with a 1 lod unit support interval spanning 1.8 cM. Recombination mapping placed the HED gene in a 2.4 cM region flanked by D13S1828 proximally and D13S1830 distally. We next show evidence for a strong founder effect in families of French Canadian origin thereby representing the first example of a founder disease in the south-west part of the province of Quebec. Significant association was found between HED in these families and all markers analysed (Fisher's exact test, P < 0.001). Complete allelic association was detected at D13S1828, D13S1827, D13S1835, D13S141 and D13S175 (P excess = 1) spanning 1.3 cM. A major haplotype including all 10 associated alleles was present on 65% of affected chromosomes. This haplotype most likely represents the founder haplotype that introduced the HED mutation into the French Canadian population. Luria-Delbrück equations and multipoint likelihood linkage disequilibrium analysis positioned the gene at the D13S1828 locus (likely range estimate: 1.75 cM) and 0.58 cM telomeric to this marker (support interval: 3.27 cM) respectively.

One of the earliest attempts to measure and incorporate dispersal into an understanding of population genetic structure was made by Dobzhansky and Wright (1943). They performed release-recapture studies with laboratory-reared mutant Drosophila pseudoobscura. More recent studies of the same species (Powell et al. 1976;Crumpacker and Williams 1973) have employed improved methods which allow marking of native flies.In their early studies Dobzhansky and Wright assumed that flies were equally likely to move from or remain at all locations. In mathematical terms this is equivalent to assuming that the density of released flies on the x, y plane at time t, +(x, y, t), obeys the diffusion equation, a4(x, v' t) -A[Do(x, y, t)] = D(x, y, t) + 02Do(x, y, t) for some constant D (Skellam 1951;Pielou 1969). To a first approximation data fitted this model, though Dobzhansky and Wright explicitly acknowledged the inadequacy of this equation to explain all dispersal behavior.Recent studies, both theoretical (Slatkin 1973;Nagylaki 1976) and experimental (Taylor and Powell 1977;Johnston and Heed 1976), have indicated that variation in dispersal rates among habitats may have important effects on population structure.Local differentiation due to natural selection and to random genetic drift may be much greater when there are barriers to movement. In this case the appropriate generalization of equation (1) would incorporate D as a spatial variable D(x, y): At(x, y, t) =2 A x t -a2D(x, y)4(x, y, t) 02D(x, y)4(x, y, t) at a[~,yoxy ) x2 + ay 2 .(2) * Deceased December 18, 1975.

An assessment of conservation units for the Sumatran rhinoceros (Dicerorhinus sumatrensis) was conducted using a population aggregation analysis (PAA) of mitochondrial DNA site substitutions. Populations were defined as the three geographically separated regions of West Malaysia, Sumatra, and Borneo. The intent of this assessment was to explore management options for this highly endangered lineage rather than conduct a traditional taxonomic revision.Individual DNA positions were not diagnostic for any population. A single haplotype provided a character as support for diagnosing the West Malaysian and Bornean population. The haplotypes on West Malaysia and Sumatra were more similar to each other than either was to the one on Borneo. These data, and a review of the morphological characters, support the option of treating Sumatran rhinos as a single conservation unit, providing managers with greater flexibility in managing the unique Dicerorhine lineage. 0 1995 Wiley-Liss, Inc.

Aedes aegypti mosquito is the principal dengue vector in the Kingdom of Saudi Arabia (KSA); however, no study has addressed its ecology and population structure yet. Therefore, we report on Ae. aegypti phylo- and population genetics using three DNA markers: COI, ND4, and rDNA-ITS2. Sampling the immature stages of Ae. aegypti revealed that water storage tanks (34.3% of habitats) were the most productive and contained 33% of immatures stages. Other important habitats included containers for wastewater drainage (including air-conditioning and water cooler trays) and containers associated with ornamentation. Shallow water leakage spots (2.7% of habitats, 8% of immatures) can be considered rare-but-epidemiologically-important containers. Neighbor-joining (NJ) phylogenetic analysis of Ae. aegypti identified 8, 14, and 9 haplotypes of COI, ND4, and ITS2, respectively, and revealed high levels of genetic variation in Ae. aegypti populations of KSA. Global distribution of haplotypes also indicated multiple gene introductions into these populations, with high levels of intra-population genetic variation and continuous gene exchange. The neutrality values indicated a deficiency of alleles and suggested that the KSA Ae. aegypti loci tested did not follow a neutral model of molecular evolution. Fst values and AMOVA indicated that most of the genetic variation in the KSA Ae. aegypti populations is due to intra- rather than inter-population differences. This is the first comprehensive report on the phylo- and population genetics of Ae. aegypti from the Arabian Peninsula. This information expands our understanding of the ecology and population dynamics of this important arboviral vector for informed control efforts.