685 research outputs found
Inversions in the third chromosome of wild races of Drosophila pseudoobscura, and their use in the study of the history of the species
Genetic studies showed several years ago that the third chromosomes of wild strains of Drosophila pseudoobscura often carry suppressors of crossing-over. The salivary gland chromosome technique has made it possible to demonstrate not only that these are inverted sections, but also that there are many different inversions present in wild populations inhabiting different geographical regions. So far we have found at least fourteen different gene-sequences in wild stocks, and have found that in most geographical regions several sequences are present, though no single sequence appears to occur throughout the range of the species. There are a number of problems raised by these facts, most of which need further study; the present account is to be regarded only as a preliminary note
Microgeographic variation in Drosophila pseudoobscura
Studies of recent years have revealed a prodigious amount of variability in the gene arrangement in the chromosomes of several species of Drosophila. In natural populations of D. pseudooobscura the third chromosome is more variable than the rest; eighteen structural types, related to each other mostly as overlapping inversions, have been found in this chromosome alone.(1
Role of the autosomes in the Drosophila pseudoobscura hybrids
Lancefield(1) discovered that the species Drosophila pseudoobscura consists of two races, called race A and race B, respectively. Completely sterile males and partially fertile females appear in the offspring if the races are intercrossed. Males coming from the cross, B♀ X A♂, have rudimentary testes that are smaller in size than the testes of normal males. Testes of the A♀ X B♂ hybrid males are normal in size but incapable of producing functional sperm
Momentarily Excessive Construction As The Basis For Protoadaptation
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137522/1/evo04677.pd
Relative Effects of Juvenile and Adult Environmental Factors on Mate Attraction and Recognition in the Cricket, Allonemobius socius
Finding a mate is a fundamental aspect of sexual reproduction. To this end, specific-mate recognition systems (SMRS) have evolved that facilitate copulation between producers of the mating signal and their opposite-sex responders. Environmental variation, however, may compromise the efficiency with which SMRS operate. In this study, the degree to which seasonal climate experienced during juvenile and adult life-cycle stages affects the SMRS of a cricket, Allonemobius socius (Scudder) (Orthoptera: Gryllidae) was assessed. Results from two-choice behavioral trials suggest that adult ambient temperature, along with population and family origins, mediate variation in male mating call, and to a lesser extent directional response of females for those calls. Restricted maximum-likelihood estimates of heritability for male mating call components and for female response to mating call appeared statistically nonsignificant. However, appreciable “maternal genetic effects” suggest that maternal egg provisioning and other indirect maternal determinants of the embryonic environment significantly contributed to variation in male mating call and female response to mating calls. Thus, environmental factors can generate substantial variation in A. socius mating call, and, more importantly, their marginal effect on female responses to either fast-chirp or long-chirp mating calls suggest negative fitness consequences to males producing alternative types of calls. Future studies of sexual selection and SMRS evolution, particularly those focused on hybrid zone dynamics, should take explicit account of the loose concordance between signal producers and responders suggested by the current findings
Phenetic distances in the Drosophila melanogaster-subgroup species and oviposition-site preference for food components
Oviposition-site preferences (O.S.P.) have been investigated in females of six sibling species of the Drosophila melanogaster subgroup. O.S.P. were determined for standard food components and yeast genotypes. Females of all species showed a strong preference for complete medium and avoidance of pure agar as an egg-deposition site.\ud
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Ecological trees of the species on the basis of rank correlations were constructed. In ‘no-choice’ situations they agree with phylogenetic trees obtained by different means but in ‘choice’ situations they do not agree too well.\ud
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All species showed a high egg production on live yeast compared with standard medium (with killed yeast) and D. erecta females demonstrated discrimination between yeast genotypes. Niche breadth calculated from survival on the sterol mutant yeasts correlated fairly well with phylogenetic trees
Hybridization in parasites: consequences for adaptive evolution, pathogenesis and public health in a changing world
[No abstract available
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