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Evolution of dioecy: can nuclear-cytoplasmic interactions select for maleness?
S Maurice1, E Belhassen, D Couvet
1Laboratoire d'Evolution et Systématique des Végétaux, Université Paris Sud, Orsay, France.
Heredity
|October 1, 1994
Summary
Nuclear-cytoplasmic sex determination can drive the evolution of male individuals in gynodioecious populations. This genetic system facilitates the emergence of dioecy and trioecy under less restrictive conditions than nuclear control alone.
Area of Science:
- Evolutionary Biology
- Genetics
- Reproductive Systems
Background:
- Gynodioecy, characterized by the presence of females and hermaphrodites, can arise when sex determination involves both nuclear and cytoplasmic genes.
- Previous models of gynodioecy typically involve two nuclear loci and two cytotypes, often considered stable and not leading to dioecy.
- The interplay between nuclear and cytoplasmic genetic factors in sex determination is crucial for understanding reproductive system evolution.
Purpose of the Study:
- To investigate whether the presence of female individuals can select for male individuals in systems with nuclear-cytoplasmic sex determination.
- To explore the evolution of alleles responsible for female sterility within these complex genetic systems.
- To determine the conditions under which dioecy and trioecy evolve with nuclear-cytoplasmic sex determination.
Main Methods:
- Development of a genetic model incorporating nuclear and cytoplasmic genes controlling sex determination.
- Analysis of the evolutionary dynamics of alleles causing female sterility, located at preceding or a third nuclear locus.
- Comparison of the conditions for the evolution of dioecy and trioecy under nuclear-cytoplasmic versus purely nuclear sex determination.
Main Results:
- The study demonstrates that male individuals can be selected for in gynodioecious populations with nuclear-cytoplasmic sex determination.
- Dioecy evolves under less stringent conditions compared to systems relying solely on nuclear sex determination.
- Trioecy (coexistence of females, hermaphrodites, and males) also evolves more readily under these conditions.
- Nuclear-cytoplasmic polymorphism can be maintained within these evolving reproductive systems.
Conclusions:
- Nuclear-cytoplasmic control of sex determination provides a pathway for the evolution of males and the breakdown of stable gynodioecy.
- This genetic mechanism promotes the evolution of more complex breeding systems like dioecy and trioecy.
- The findings highlight the significant role of cytoplasmic factors in shaping the evolution of reproductive strategies.