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Monozygotic twinning: an evolutionary hypothesis
S K Gleeson1, A B Clark, L A Dugatkin
1School of Biological Sciences, University of Kentucky, Lexington 40506.
Summary
Monozygotic twinning, the formation of identical clones, can evolve if the benefit of increased offspring frequency outweighs the cost of reduced survival. This evolutionary model explains why twinning can be common yet appear rare.
Area of Science:
- Evolutionary biology
- Developmental genetics
Background:
- Monozygotic twinning is a rare phenomenon observed across diverse species.
- The evolutionary drivers and population dynamics of twinning remain incompletely understood.
Purpose of the Study:
- To model the evolutionary dynamics of an allele promoting monozygotic twinning.
- To investigate the conditions under which twinning alleles can increase in frequency and become prevalent.
Main Methods:
- Developed haploid genetic models to simulate the spread of a twinning allele.
- Analyzed the trade-offs between increased reproductive frequency and resource-limited survival costs.
Main Results:
- The twinning allele can reach high frequencies under various conditions, contingent on the balance of benefits and costs.
- High survival costs, such as those in small clutch sizes, can limit the spread of the twinning trait.
- Random parental abortion and selection for low penetrance can lead to high allele frequency with low observed twinning rates.
Conclusions:
- The evolutionary model provides explanations for both the rarity and potential hidden prevalence of monozygotic twinning.
- Findings suggest that resource allocation and parental-offspring conflict influence twinning evolution.
- The study also touches upon implications for other twinning types and sex-linked inheritance patterns.