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AN UNUSUAL SEX‐DETERMINATION SYSTEM IN SOUTH AMERICAN FIELD MICE (GENUS AKODON) : THE ROLE OF MUTATION, SELECTION, AND MEIOTIC DRIVE IN MAINTAINING XY FEMALES
Author(s) -
Hoekstra Hopi E.,
Hoekstra Jonathan M.
Publication year - 2001
Publication title -
evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.84
H-Index - 199
eISSN - 1558-5646
pISSN - 0014-3820
DOI - 10.1111/j.0014-3820.2001.tb01283.x
Subject(s) - biology , meiotic drive , genetics , meiosis , chromosome , y chromosome , fecundity , x chromosome , evolutionary biology , gene , population , demography , sociology
The mechanism of sex determination in mammals appears highly conserved: the presence of a Y chromosome triggers the male developmental pathway, whereas the absence of a Y chromosome results in a default female phenotype. However, if the Y chromosome fails to initiate the male pathway (referred to as Y * ), XY * females can result, as is the case in several species of South American field mice (genus Akodon ). The breeding genetics in this system inherently select against the Y * chromosome such that the frequency of XY * females should decrease rapidly to very low frequencies. However, in natural populations of Akodon , XY * females persist at substantial frequencies; for example, 10% of females are XY * in A. azarae and 30% in A. boliviensis . We develop a mathematical model that considers the potential roles of three evolutionary forces in maintaining XY * females: Y‐to‐Y * chromosome transitions (mutation), chromosome segregation distortion (meiotic drive), and differential fecundity (selection). We then test the predictions of our model using data from breeding colonies of A. azarae . We conclude that any single force is inadequate to maintain XY * females. However, a combination of segregation bias of the male and female Y chromosomes during spermatogenesis/oogenesis and increased fecundity in XY * females could account for the observed frequencies of XY * females.