Presentation on theme: "Printed by www.postersession.com Drive and Phenotypic Effects of B Chromosomes, Analyzed by Sex and Mode of Drive Palestis BG, Jones RN, Trivers R Wagner."— Presentation transcript:
printed by Drive and Phenotypic Effects of B Chromosomes, Analyzed by Sex and Mode of Drive Palestis BG, Jones RN, Trivers R Wagner College, USA; University of Wales, UK; Rutgers University, USA We review studies of drive and the phenotypic effects of B chromosomes, focusing on the sex in which drive and phenotypic effects occur. We found information on drive and/or effects of Bs in 172 species, using R.N. Jones database of B research through 1994, updated by computer searches through Most species show drive (n=81) in contrast to drag (n=10) or neither (n=13). Additionally, in two species Bs drive in one sex and drag in the other. Drive was reported through males in 45 species, females in 21, and both sexes in 10. The overall patterns differ among taxa. In grasshoppers with detailed data, female meiotic drive occurs in 5 of 8 species, whereas in grasses drive occurs during pollen grain mitosis in 24 of 27 species. Phenotypic effects of Bs are usually negative: 69 harmful, 13 beneficial, 33 neutral, and in 8 cases data was mixed. Beneficial effects occur when B numbers are low. Harmful effects of Bs were most often felt by males (n=32; abnormal sperm, decreased pollen fertility) or by both sexes (n=29; including both reproductive and non-reproductive effects, such as decreased growth), and rarely by females only (n=7; e.g. decreased seed set). Bs affected the two sexes oppositely in only one species. Drive is usually associated with negative phenotypic effects, while positive phenotypic effects of Bs are more common in species with drag, as expected. We originally planned to test whether the sex through which drive occurs is the same as or opposite to the sex affected phenotypically. However, too few species have sex-specific data on both B drive and phenotypic effects to permit a meaningful comparison. Most species show drive through males (Table 1). Harmful effects are most frequent in males (Table 2). However, these patterns may not be generalized due to differences among taxa (Table 3) and large differences in the number of studies across taxa (Tables 1, 2). As expected, positive effects are associated with drag, while negative effects are associated with drive (p = ; Table 4). Table 1. Comparison across all species and within three taxa of the sex in which drive occurs, and whether drive occurs. Sex with DriveAll SpeciesGrassesCompositesGrasshoppers Male 45*246*4 Female21*21*6 Both10160 Sex unknown7000 No Drive or Drag13413 Drag10401 *Includes 1 species with drag in the opposite sex. Table 2. Comparison across all species and within three taxa of the sex in which harmful phenotypic effects occur, and whether harmful effects occur. Sex HarmedAll SpeciesGrassesCompositsGrasshoppers Male Female6500 Both Sex unknown2000 Effects mixed8300 Neutral33445 Beneficial effects13331 Note: Effects mixed includes a few potentially heterotic Bs and one species with the sexes affected oppositely. A complete list of references, as well as the data, is available from Palestis An online version of Jones database is published with the special B chromosome issue of Cytogenetic and Genome Research. Funding was provided by the Biosocial Research Foundation. Table 4. Comparison across all species of presence of drive or drag and the direction of effects HarmfulBeneficialNeutral Drive3737 Drag251 Neither302 We planned to test whether the sex in which drive occurs is the same as or opposite to the sex affected phenotypically. Too few species have sex-specific data on both B drive and phenotypic effects (Table 5) to permit a meaningful comparison. More research is clearly needed here. May expect effects and drive in same sex if B transmission disrupts meiosis or mitosis. If in opposite sexes, suggests sex-antagonistic effects; Bs may spread through one sex, while being selected against in the other. Mode of drive may also play a role in the type of effect (e.g. meiosis & fertility). Table 5. Within-species comparison of the sex with drive and the sex affected Sex w/DriveSex Harmed MaleFemale Both Male84 8 Female32 5 Both10 3 There have been many studies of B transmission and of phenotypic effects of Bs across many species. By comparing across many species it is possible to see overall patterns. We quantify the previous studies of transmission and effects of Bs, focusing on the sex in which these occur. We found information on drive and/or effects of Bs in 172 species, using Jones database of B research through 1994, updated by computer searches through We analyze both across the entire dataset and within 3 taxa: grasses (Poaceae = Gramineae), composites (Asteraceae = Compositae), grasshoppers (Orthoptera). ABSTRACT INTRODUCTION SUMMARY DATARESULTS Is Sex of Drive Associated with Sex of Phenotypic Effect? REFERENCES & ACKNOWLEDGMENTS The B chromosomes of Crepis capillaris – a species with drive. Allium schoenoprasum – a species with beneficial effects Mitotic drive at pollen grain mitosis in rye Directed nondisjunction at the first pollen grain mitosis, and at the first egg cell mitosis on the female side. Populations reach equilibrium frequencies of Bs through a balance of drive and harmful effects. Centromere misdivision of a univalent B in Aegilops mutica 2n = 2x =14, leading to meiotic loss. Drive occurs with 2B & 3B at first pollen grain mitosis.