Genetic mapping of sex determination in a wild strawberry, Fragaria virginiana, reveals earliest form of sex chromosome

No amicable divorce? Challenging the notion that sexual antagonism drives sex chromosome evolution

“…The existence of these transitional states implies that alleles causing male sterility and female sterility occur at separate loci [78]. This scenario also derives empirical support from the dioecious flowering plants Silene latifolia, Fragaria virginiana and Sagittaria latifolia [19,80,81]. These three plants possess heteromorphic sex chromosomes in which the non-recombining region of the Y chromosome contains separate factors for male fertility and female sterility.…”

“…This apparent association between the function of sex determination and suppression of recombination has led to the suggestion that restricted recombination in sex chromosomes evolves due to selection to resolve sexually antagonistic genetic interactions [2,[9][10][11]. This sexual antagonism hypothesis has assumed the status of conventional wisdom, to the extent that, in many recent publications, sexual antagonism is the only hypothesis suggested to account for restricted recombination in sex chromosomes [1,6,[12][13][14][15][16][17][18][19][20][21][22]. However, empirical support for the sexual antagonism hypothesis is equivocal [1].…”

Sex chromosome evolution: A ‘missing link’ in the evolution of sex chromosomes

“…With their publication of a genetic map for the octoploid strawberry, Fragaria virginiana, Spigler et al (2008) have discovered a missing link in the evolution of sex chromosomes from autosomes. Before this study, sex determination in this subdioecious plant (consisting of males, females and hermaphrodites) was considered to be controlled by a single Mendelian locus.…”

“…Before this study, sex determination in this subdioecious plant (consisting of males, females and hermaphrodites) was considered to be controlled by a single Mendelian locus. However, Spigler et al (2008) found that male and female functions mapped independently and are tightly linked in a single linkage group. These findings are consistent with current models of sex chromosome evolution from autosomes and represent one of the earliest stages of sex chromosome evolution.…”

“…However, Spigler et al (2008) were able to tease apart the genetics of sex determination in this species by separately mapping female function (X5% fruit-forming flowers) and male function (presence of pollen-filled anthers) in a mapping population derived from a cross between a F. virginiana female and hermaphrodite (which served as the male parent). The separation of reproductive function is critical, as hermaphrodites can have both male and female function.…”