Population Cytology of the Genus Phaulacridium VI.  Seasonal Changes in the Frequency of the B Chromosome in a Population of Ph. vittatum

Westerman, Michael; Dempsey, J. A. F.

doi:10.1071/bi9770329

Cited by 10 publications

(5 citation statements)

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“…The findings of Westerman and Dempsey (1977) that B frequency in adult males of Ph. vittatum changes during the summer and that this change coincides with changes in mean daily temperature suggest that there may be some differential selection acting on B-containing individuals at the adult stage.…”

Section: Discussionmentioning

confidence: 99%

“…vittatum (John and Freeman 1974;Rowe and Westerman 1974). Westerman and Dempsey (1977) have shown, however, that in the La Trobe campus population in 19 samples out of 20 taken over a two-year period in which B chromosomes were present, the B-containing individuals consistently had higher recombination levels than those without B chromosomes. Thus B chromosomes do appear to significantly raise mean cell chiasma frequency in Phaulacridium.…”

Section: Discussionmentioning

confidence: 99%

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Population Cytology of the Genus Phaulacridium V. Ph. marginale ? The Omarama Population

Westerman¹

1977

Aust. Jnl. Of Bio. Sci.

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During the 1975 meiotic season a sample of 105 Ph. marginale males was collected from Omarama (South Island, New Zealand). This population is polymorphic for a small metacentric B chromosome (BM) and for extra segments on the three smallest autosomes. Only 10% of males have the basic karyotype. Previous collections from this population had similar frequencies of the BM chromosomes and of the extra segments.One individual carried a small telocentric B chromosome (B'), unusual at Omarama, as well as the BM typical of this population. This may be significant for the proposed evolution of B chromosomes in the genus Phaulacridium. Both types of supernumerary heterochromatin (B chromosomes and segments) produce a similar increase in mean cell chiasma frequency, and maximal increase is produced by one B chromosome or one segment. There is no evidence for any additive or synergistic action of B chromosomes and segments.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Population Cytology of the Genus Phaulacridium V. Ph. marginale ? The Omarama Population

Westerman¹

1977

Aust. Jnl. Of Bio. Sci.

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“…In rye, Bs are associated with higher chiasma frequencies in some cultivars (Zecevic & Paunovic, 1969) but not in others (Jones & Rees, 1967). Moreover, the response of chiasma frequency to the presence of Bs may vary among natural populations of the same species; in grasshoppers this has been reported from M. maculatus (John & Hewitt, 1965), Phaulacridium vittatum (John & Freeman, 1975;Westerman & Dempsey, 1977) and Eyprepocnemis plorans (Camacho, Carballo & Cabrero, 1980). In E. plorans, Henriques-Gil, Santos & Giraldez (1982 a) found that the response varied among families produced by naturally fertilized females from the same population, apparently because Bs were associated with a substantial increase in chiasma frequency only in families where individuals without Bs had exceptionally low chiasma frequencies.…”

Section: Increased Recombination As a Host Response To B-infectionmentioning

confidence: 99%

B-chromosomes: germ-line parasites which induce changes in host recombination

Bell

Burt

1990

Parasitology

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The object of this paper is to suggest that there may be an unexpected connexion between parasites and the evolution of sex, using for illustration an unfamiliar type of parasite, the selfish chromosome. The major intellectual challenge of sexuality is to an environment which is continually getting worse. The elegant solution given by the Red Queen theory (Levin, 1975; Hamilton, 1980; Bell, 1982; Bell & Maynard Smith, 1988) is that the relevant aspect of the environment is provided by antagonists—pathogens, predators and competitors—which, because they can respond adaptively so as to negate any improvement that has been made, provide a constant stimulus for continued evolution. Sexuality and recombination are favoured because some of the new combinations of genes which they create are resistant to the current population of antagonists. In other respects, sex and recombination are probably highly disadvantageous: outcrossed sex is expensive because it halves the rate of transmission of genes, while recombination breaks up successful combinations of genes. It is only in certain circumstances that the necessity for continual counter-adaptation will overcome these disadvantages: in particular, the damage (reduction in fitness) caused by an antagonist must be substantial, and the amount of damage must depend on a genetic interaction between the antagonistic species. These requirements are often satisfied by host—parasite systems, where both the ecological and genetic interactions between the antagonists may be very severe and highly specific (see reviews by Day, 1974 and Burdon, 1987). It is possible, therefore, that sex and recombination are maintained in natural populations largely through the dynamics of the coevolution of hosts and their parasites. This is certainly compatible with the major ecological patterns shown by sexual systems, with outcrossed sex being more common in the sea than in freshwater, more common at low than at high latitudes, and generally more common in stable, complex, climax environments where interactions between species are expected to be more frequent and intense (Bell, 1982). However, there is as yet no evidence which conclusively supports a direct causal link between the incidence of parasitism and the rate of recombination. In particular, it has never been demonstrated that a particular parasite has the effect of eliciting, directly or indirectly, a greater rate of genetic recombination in its host. We suggest that such a parasite exists; both the parasite and its effects are well known, but have never been interpreted in the context of the evolution of recombination through host—parasite coevolution. It is in many respects a rather unusual parasite. We shall argue that B-chromosomes represent highly evolved parasitic DNA, transmitted through the germ line and often eliciting greater rates of recombination in the host genome.

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“…It does not explain the contradictory results between cultivars or populations of a same species, e.g. rye ( Jones & Rees 1967;Zec Ï ević & Paunović 1969), and the grasshoppers Myrmeleotettix maculatus ( John & Hewitt 1965), Phaulacridium vittatum ( John & Freeman 1975;Westerman & Dempsey 1977) and Eyprepocnemis plorans (Camacho et al 1980;Henriques-Gil et al 1982).…”

Section: Introductionmentioning

confidence: 99%

Host recombination is dependent on the degree of parasitism

Camacho

Bakkali

Corral

et al. 2002

Proc. R. Soc. Lond. B

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Parasites and hosts are involved in a continuous coevolutionary process leading to genetic changes in both counterparts. To understand this process, it is necessary to track host responses, one of which could be an increase in sex and recombination, such as is proposed by the Red Queen hypothesis. In this theoretical framework, the inducible recombination hypothesis states that B-chromosomes (genome parasites that prosper in natural populations of many living beings) elicit an increase in host chiasma frequency that is favoured by natural selection because it increases the proportion of recombinant progeny, some of which could be resistant to both B-chromosome effects and B-accumulation in the germline. We have found a clear parallelism between host recombination and the evolutionary status of the B-chromosome polymorphism, which provides explicit evidence for inducible recombination and strong support for the Red Queen hypothesis.

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Population Cytology of the Genus Phaulacridium VI. Seasonal Changes in the Frequency of the B Chromosome in a Population of Ph. vittatum

Cited by 10 publications

References 15 publications

Population Cytology of the Genus Phaulacridium V. Ph. marginale ? The Omarama Population

Population Cytology of the Genus Phaulacridium V. Ph. marginale ? The Omarama Population

B-chromosomes: germ-line parasites which induce changes in host recombination

Host recombination is dependent on the degree of parasitism

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