An adaptive explanation for male-biased sex ratios in overwintering monarch butterflies
Article Abstract:
A study of the sex ratios in a population of overwintering monarch butterflies showed a male bias in sex, with the males accounting for 60% of the population. The finding contradicts results of previous studies which showed that sex ratio in monarch butterflies has a 1:1 ratio. Researchers attributed the male-sex bias to biased mortality, differences in catchability and the early development of overwintering male butterflies. The bias is attributed to the males' early entry to the diapause stage. The males were also observed to postpone sexual maturation until the next season to have greater opportunities for mating. This suggests that initial male-sex biased ratio is natural for overwintering populations of monarch butterflies.
Publication Name: Animal Behaviour
Subject: Zoology and wildlife conservation
ISSN: 0003-3472
Year: 1995
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Reply to Nylin, Wickman & Wiklund regarding sex ratios of California overwintering monarch butterflies
Article Abstract:
The alternative explanation for the male-sex bias ratio in monarch butterfly populations attributed male dominance to differential mortality during adult stages. The explanation, which was based on the evolutionary strategy model, assumed that the males entered and terminated diapause earlier than the females. It contradicts results of previous studies which show that females become sexually mature earlier than the males. Furthermore, mating has also been observed to be independent of the females' ovulation period. In conclusion, the model used in the study is more applicable to insects with discrete generations than on insects with overlapping generations.
Publication Name: Animal Behaviour
Subject: Zoology and wildlife conservation
ISSN: 0003-3472
Year: 1995
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Effects of population size and food stress on fitness-related characters in the scarce heath, a rare butterfly in Western Europe
Article Abstract:
An analysis of the effect of fitness-related traits in the scarce heath, a butterfly, in population size and isolation and if the differences in food quality influence these effects is studied. The results show that the differences in fitness between offspring from large and small isolated populations are partly due to inbreeding with a further threat to a species that is already suffering from decreasing population sizes and increasing isolation among populations.
Publication Name: Conservation Biology
Subject: Zoology and wildlife conservation
ISSN: 0888-8892
Year: 2001
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