Optimal rates of dispersal II. Diploid populations

The problem of how an individual should divide its progeny into dispersed and non-dispersed descendants is investigated for a number of haploid models. In each model, a unique optimal ratio of dispersed to non-dispersed has been found, where the type with this optimal strategy has a selective advantage over all other types. Although the survival ability of a dispersed offspring is reduced (compared to that of a non-dispersed offspring), the optimal strategy implies that a substantial part of the progeny will be dispersed.     

Fertility in Crosses Involving Diploid and Autotetraploid Raspberries: I. The Embryo

Crosses between diploid raspberry cultivars (Rubus idaeus L.)and their autotetraploid forms have shown that embryo shapedepends on three main factors—the variety, the stage ofdevelopment reached before growth ceases, and the ploidy ofthe embryo itself. Embryo growth, however, depends on the abilityof the endosperm to nourish the embryo and so on the harmoniousco-existence of derivatives of the gametes which formed theendosperm. Crosses between plants of unequal ploidy produceendosperms which are unbalanced. In general, the order of fertilityof the crosses is 2n selfed, 4n selfed, 4n X 2n, 2n X 4n, andthis can be partly explained if the effect of chromosome doublingis to increase the genetic strength of the male gametes morethan that of the female. Variations in the embryo growth inthe 2n X 4n and 4n x 2n crosses are ascribed to smaller differencesin genetic strength between varieties and between the male andfemale gametes within a variety. Embryos derived from crosseswithin a single variety grew less well than those derived fromcrosses between varieties, other factors being equal, and thisis considered to be an early expression of inbreeding depressionin the embryo.     

Genetic variation in dosage effects in maize aneuploids.

In maize (Zea mays L.), the consequences of aneuploidy have been well documented, however, genetic variation in the responses to aneuploidy has not been examined. Using simple B-A translocation stocks to generate a dosage series involving segments from 14 chromosome arms, we tested for the presence of genetic variation for dosage responses in maize by examining reciprocal and maternal genotype effects on the dosage responses. Reciprocal effects examined whether there were differences between two distinctly different inbred backgrounds, Mo17Ht and B73Ht, in how they responded to loss or gain of a B73Ht segment in the Mo17Ht x B73Ht (TB) F1 cross versus a Mo17Ht segment in the B73Ht x Mo17Ht (TB) F1 cross. Maternal genotype effects questioned whether different inbred backgrounds, Sc41R, T8, and either Mo17Ht or B73Ht (depending on the male), when used as females responded differently to the loss or gain of a chromosome arm segment from the same male (either B73Ht TB or Mo17Ht TB) in an F1 cross. Numerous examples of reciprocal and maternal genetic effects were identified in this study. Most of the genetic effects were due to differences in magnitude of response rather than direction; however, tassel-branch number involving the 5S chromosome segment in the B73Ht male background and the 7L chromosome segment in the Mo17Ht male background showed a trend toward the maternal genotype effects being due to differences in the direction of the response. Key words : quantitative traits, corn, B-A translocations, dosage analysis.     

Telo aneuploids in pearl millet

Summary Nomenclature and chromosome constitution for twenty different aneuploids with telocentrics in Pennisetum typhoides are presented.     

On the concept of attractor for community-dynamical processes I: the case of unstructured populations

We introduce a notion of attractor adapted to dynamical processes as they are studied in community-ecological models and their computer simulations. This attractor concept is modeled after that of Ruelle as presented in [11] and [12]. It incorporates the fact that in an immigration-free community populations can go extinct at low values of their densities.Mathematics Subject Classification (2000):37b20, 37c50, 37c70     

Diploid radiation gynogenesis in carp. I. Massive production of diploid gynogenetic progeny]

Mass lost of diploid gynogenetic carp offspring were obtained with the use of fish-farm method of reproduction. The average yield of gynogenetic diploids in usual experiments was 0.1% (from fertilized eggs). The cooling of unfertilized spawn (at the stage of metaphase II) to 8--10 degrees C during 3.5--4.5 hours in 50% of cases permitted to increase by tens of times (in the most successful experiments up to 8%) the yield of gynogenetic diploids. The rate of survival of carps remained relatively low during the first two years of life, particularly during the first hibernation that is a critical period. No specific depression of growth in gynogenetic diploid carps was observed. A high yield of gynogenetic diploids (3.9% of fertilized eggs) and their relatively high rate of survival were observed in the second generation of artificially induced gynogenesis.     

Microevolution in prehistoric andean populations: I. Chronologic craniometric variation

Mahalanobis D² statistics (with size and shape components) were computed for nine craniometric variables among five prehistoric groups representing steps in the microevolutionary history of a coastal population in Northern Chile. Roughly 80% of craniometric variation was found to be explained by chronologic distance covering a period of roughly 6500 years. Kinship decreases in this population at a relatively constant rate of 8.6 × 10^?5 per year.     

Quinua biosystematics I: Domesticated populations

Domesticated populations of the South American grain chenopod quinua (Chenopodium quinoa subsp.quinoa) have been formally classified on the basis of pigmentation and inflorescence morphology, and informally grouped according to ecotypic variation. Comparative analysis of morphometric and electrophoretic data taken from 98 populations reveals two fundamental elements: a coastal type from southwestern Chile and an Andean type distributed at elevations above 1,800 m from northwestern Argentina to southern Colombia. Andean quinua can be further divided into northern and southern groups, with the northern populations weakly marked by broad, unlobed leaf blades, sharply margined fruit, and relative uniformity. With the exception of allozymes unique to coastal quinua, characteristics that differentiate populations from the Chilean coast and the northern Andes represent a subset of variation present in the southern Andes. This could reflect diffusion from a possible center of origin in the southern highlands. Overall phenetic association places populations from the Altiplano of Peru and Bolivia in a central, linking position. The high genetic identities among all quinua populations argue against a polyphyletic origin for the crop and specific differentiation among cultivar groups. The overall pattern of variation supports the ecotypic approach toward landrace classification of quinua, although congruence between ecological and morphogenetic variation is not complete. While genetic diversity is clearly centered in populations of the southern Andes, conservation efforts should focus on well differentiated quinua populations at the poorly marked northern and southern extremes of distribution.     

Dosage effects on morphological and quantitative traits in maize aneuploids.

Dosage effects generated by either loss or gain of a chromosome segment were used to identify chromosome regions associated with morphological and quantitative characters in maize (Zea mays L.). Using B-A translocation stocks introgressed into a B73Ht background, a chromosome arm dosage series in a Mo17Ht x B73Ht F1 hybrid background was created for 18 of the 20 chromosome arms. The dosage series was then evaluated for 12 quantitatively inherited characters to associate specific phenotypic changes in a trait with a specific chromosome arm. Not only did our results show the familiar aneuploid syndrome phenomenon, but differential dosage effects among particular chromosome arms were demonstrated. All the quantitative traits measured and all the chromosome arms examined in this study were responsive to changes in chromosome arm dosage. The possible bases behind those differences and their utility in identifying quantitative trait loci, as well as the genetic relationships among the group of quantitatively inherited characters studied, are considered. Key words : corn, chromosome arm, B-A translocations, dosage analysis.     

Studies on bacterial conjugational crosses via model populations. I. The model populations

A procedure is presented in which model populations, simulating progenies obtained from Escherichia coli Hfr x F- crosses, are generated. The procedure seems to be appropriate for visualizing hidden features of the genetic analysis, which are not detected by the conjugational crosses.     

Progress in the study of aneuploids in barley

Recent developments in the study of aneuploids in barley are reviewed. To date five complete series of primary trisomics have been produced. Considerable progress has been made toward the production of a complete set of monotelotrisomics. Eleven of the possible 14 have thus far been identified though not all in the same genetic background. Studies on existing monotelotrisomics have shown that those representing the long arm frequently resemble the corresponding primary trisomic in gross morphology while short arm counterparts are rarely distinguishable from diploids. The average transmission rate of extra telos through female gametes was 31.9% with all showing a low rate of male transmission. In 81.3% of cells at metaphase 1 of meiosis the extra telos are synapsed with normal homologues to form heteromorphic trivalents. Tandem-chain configurations were the predominant type.     

Genetic identity in subdivided populations. I. Two equal-sized subpopulations

Moments of the steady state frequency spectrum (probabilities of identity of samples of genes) are obtained for a subdivided population by using standard recursive identity by state calculations. These moments are used to obtain variances for some measures of genetic identity, including Nei's normalized genetic identity (I) and genetic distance (?log_eI). The results are compared with those obtained from the corresponding undivided population theory, including adjustments to the effective number to try to account for subdivision. Undivided population approximations based on effective number are surprisingly accurate, regardless of the migration rate, when sampling exclusively from one subpopulation.     

Some genetic traits in Solomon island populations. I. Introduction: people and habitats

To introduce a set of genetic studies among Solomon Islanders, four tribal groups on Bougainville and Malaita Islands are described. They were observed in 1966 and 1968 by social anthropologists and biomedical scientists from Harvard University. The groups varied in habitat and way of life from fishermen living on artificial islets in a saltwater lagoon (the Lau, on Malaita) to shifting agriculturists (the Nasioi, on Bougainville, and the Kwaio and Baegu, on Malaita). The Nasioi were darker than the Malaitans and spoke a non-Austronesian rather than a Melanesian language; they were also more Westernized. Coverage of residents in designated hamlets ranged from 78% to over 95%. In all, 1,626 persons were studied: 256 Nasioi, 443 Kwaio, 442 Lau, and 485 Baegu. Genetic differences have been found between the Nasioi and the Malaitans, and between the Lau and the other Malaitans.