Disassortative mating, sexual specialization and the evolution of gender dimorphism in heterodichogamous Acer opalus.
Gleiser, G.; Verdú M.; Segarra-Moragues, J.G.; González-Martínez, S.C.; Pannell, J.R.. Disassortative mating, sexual specialization and the evolution of gender dimorphism in heterodichogamous Acer opalus.. Evolution. 2008, Vol. 62(7), p. 1676-2008.
In sexually polymorphic species, the morphs are maintained by frequency-dependent selection through disassortative mating.
In heterodichogamous populations in which disassortative mating occurs between the protandrous and protogynous morphs, a
decrease in female fitness in one morph is hypothesized to drive sexual specialization in the other morph, resulting in dimorphic
populations. We test these ideas in a population of the heterodichogamous species, Acer opalus. We assessed both prospective
gender of individuals in terms of their allocations and actual parentage using microsatellites; we found that most matings in A.
opalus occur disassortatively. We demonstrate that the protogynous morph is maintained by frequency-dependent selection, but
that maintenance of males versus protandrous individuals depends on their relative siring success, which changes yearly. Seeds
produced later in the reproductive season were smaller than those produced earlier; this should compromise reproduction through
ovules in protandrous individuals, rendering them male biased in gender. Time-dependent gender and paternity analyses indicate
that the sexual morphs are specialized in their earlier sexual functions, mediated by the seasonal decrease in seed size. Our results
confirm that mating patterns are context-dependent and change seasonally, suggesting that sexual specialization can be driven
by seasonal effects on fitness gained through one of the two sexual functions.
In sexually polymorphic species, the morphs are maintained by frequency-dependent selection through disassortative mating.
In heterodichogamous populations in which disassortative mating occurs between the protandrous and protogynous morphs, a
decrease in female fitness in one morph is hypothesized to drive sexual specialization in the other morph, resulting in dimorphic
populations. We test these ideas in a population of the heterodichogamous species, Acer opalus. We assessed both prospective
gender of individuals in terms of their allocations and actual parentage using microsatellites; we found that most matings in A.
opalus occur disassortatively. We demonstrate that the protogynous morph is maintained by frequency-dependent selection, but
that maintenance of males versus protandrous individuals depends on their relative siring success, which changes yearly. Seeds
produced later in the reproductive season were smaller than those produced earlier; this should compromise reproduction through
ovules in protandrous individuals, rendering them male biased in gender. Time-dependent gender and paternity analyses indicate
that the sexual morphs are specialized in their earlier sexual functions, mediated by the seasonal decrease in seed size. Our results
confirm that mating patterns are context-dependent and change seasonally, suggesting that sexual specialization can be driven
by seasonal effects on fitness gained through one of the two sexual functions.