Sex ratio evolution in lemmings

Bulmer, Michael

doi:10.1038/hdy.1988.110

Cited by 27 publications

(12 citation statements)

References 6 publications

(11 reference statements)

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“…In situations of colonization, female number is a limiting factor to demographic expansion, and female‐biased sex‐ratios could be favored. X‐borne factors biasing the sex‐ratio in favor of females have been described, acting either as transmission distorters (Montchamp‐Moreau and Cazemajor 2002; Montchamp‐Moreau 2006; Tao et al 2007) or as feminizing factors (Givela 1987; Bulmer 1988; Liu et al 1998; Veyrunes et al 2010). The possibility that the introgressed X‐chromosome fragment be linked to a sex‐ratio distorter relates to a controversial issue.…”

Section: Discussionmentioning

confidence: 99%

Interspecific X-Chromosome and Mitochondrial Dna Introgression in the Iberian Hare: Selection or Allele Surfing?

et al. 2011

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Introgression from a resident species into an invading one is predicted to occur through the demographic process of "allele surfing," and to particularly affect genomic regions transmitted by the lower migrating sex, such as mtDNA. This could explain that northern Iberian populations of Lepus granatensis harbor high frequencies of mtDNA from L. timidus, an arctic hare it replaced there after deglaciation. We report that variation of introgressed timidus-like mtDNA reflects several predicted effects of this process: increasing frequency and diversity in the direction of expansion, strong perpendicular phylogeographic structure and signs of postglacial demographic growth. However, demographic inferences for the granatensis and timidus-like mtDNA lineages suggest the latter may have outcompeted the former in northern Iberia. Autosomal introgression occurs at low frequencies and species-wide rather than only in the north. If this difference with mtDNA resulted from sex-biased migration, an intermediate pattern should prevail for the X-chromosome, but we report species-wide and high-frequency introgression of an X-fragment.Either selection favored this ubiquitous X-introgression, or more complex postglacial expansion patterns prevailed, with different consequences depending on the genomic and geographic region. This illustrates the difficulty of distinguishing demographic and selective effects and the need for genome and species-wide based demographic models.

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Section: Discussionmentioning

confidence: 99%

Interspecific X-Chromosome and Mitochondrial Dna Introgression in the Iberian Hare: Selection or Allele Surfing?

et al. 2011

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“…However, heterogametic and homogametic females showed a similar litter size at birth. A compensation of litter size may arise from an "automatic" property of the reproductive system, due to reduced competition between surviving embryos as a result of the early loss of YY* zygotes, or an "evolved" property, due for example to an increased ovulation rate in XY* females (BULL and BULMER 1981;BULMER 1988). Our observations on the number of corpora lutea at mid-gestation showed similar mean values for XX and XY* females, which means that there is no increase in the ovulation rate of heterogametic females of A .…”

Section: Discussionmentioning

confidence: 99%

Offspring Sex-Ratio and Reproductive Performance in Heterogametic Females of the South American Field Mouse Akodon Azarae

Espinosa

Vitullo

2004

Hereditas

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We have compared the breeding performance of homogametic (XX) and heterogametic (XY*) females of the South American sigmodontine rodent Akodon azarae under laboratory conditions. XY* females showed an enhanced reproductive performance when compared with normal, XX, females. The XY* females had a longer reproductive lifespan. They started to reproduce early, had more frequent litters, and stopped reproduction later than XX females. Their progeny showed a biased 1:2 male:female sex ratio which may be explained by the early loss of YY* zygotes after fertilization. However, litter size at birth was similar both in XY* and XX females, and no difference in ovulation rate was detected between them. This indicates that an "automatic" rather than an "evolved" reproductive compensation mechanism may be acting in heterogametic females. A separate study has shown that self-synapsis of both the X and Y* chromosomes takes place during meiosis, allowing the oocytes to escape from functional deterioration. It is suggested that self-synapsis and "automatic" reproductive compensation account for the preservation of fertility in heterogametic females in spite of the heteromorphic sex chromosomes and the early embryo loss they experience. However, these mechanisms do not account for the enhancement of reproductive lifespan. The possibility that an intrauterine position phenomenon is acting in A. azarae is discussed.

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“…However, reasons due to the evolutionary history of the species should not be neglected. For instance, in the case of the wood lemming, BULMER (1988) suggested that the occurrence of the X* chromosome is due to a historical "accident" and its persistence in lemming populations is possible only because no suppressor has yet evolved.…”

Section: Sex Ratiomentioning

confidence: 99%

Chromosome variation in embryos of a solitary spider, Pityohyphantes phrygianus, with skewed sex ratio

Gunnarsson

Andersson

2008

Hereditas

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Chromosome numbers were investigated in developing embryos of the solitary sbeetweb spider Pityohyphanfesphrygianus (Araneae: Linyphiidae). It was concluded that 2n = 25 in males, and 2n = 28 in females, i.e., males are X,X,X,O. Aberrant chromosome numbers were found in 3.2 % of the embryos. In 1.8 % of the embryos, the haploid chromosome number, n = 14, was observed, suggesting that unfertilized eggs could start developing. A few polyploid embryos were also observed. The proportion of embryos with aberrant chromosome numbers was significantly higher in the second brood of the females than in the first one. The observed chromosome variation suggests that the meiosis in Pityohyphantes phrygianus is unstable. An unstable genetic mechanism may have implications at the population level in this case as the primary sex ratio is female biased in P. phrygianus. Conceivable mechanisms of the skewed sex ratio are segregation distorsion and sperm selection. The evolutionary implications of the results are discussed.

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Sex ratio evolution in lemmings

Cited by 27 publications

References 6 publications

Interspecific X-Chromosome and Mitochondrial Dna Introgression in the Iberian Hare: Selection or Allele Surfing?

Interspecific X-Chromosome and Mitochondrial Dna Introgression in the Iberian Hare: Selection or Allele Surfing?

Offspring Sex-Ratio and Reproductive Performance in Heterogametic Females of the South American Field Mouse Akodon Azarae

Chromosome variation in embryos of a solitary spider, Pityohyphantes phrygianus, with skewed sex ratio

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