X. Vekemans et al., MATE AVAILABILITY AND FECUNDITY SELECTION IN MULTI-ALLELIC SELF-INCOMPATIBILITY SYSTEMS IN PLANTS, Evolution, 52(1), 1998, pp. 19-29
We investigate mate availability in different models of multiallelic s
elf-incompatibility systems in mutation-selection-drift balance in fin
ite populations. Substantial differences among self-incompatibility sy
stems occur in average mate availability, and in variances of mate ava
ilability among individual plants. These differences are most pronounc
ed in small populations in which low mate availability may reduce seed
set in some types of sporophytic self-incompatibility. In cases where
the pollination system causes a restriction in the number of pollen g
enotypes available to an individual plant, the fecundity of that plant
depends on the availability of compatible pollen, which is determined
by its genotype at the incompatibility locus. This leads to an additi
onal component of selection acting on self-incompatibility systems, wh
ich we term ''fecundity selection.'' Fecundity selection increases the
number of alleles maintained in finite populations and increases mate
availability in small populations. The strength of fecundity selectio
n is dependent on the type of self-incompatibility. In some cases, fec
undity selection markedly alters the equilibrium dynamics of self-inco
mpatibility alleles. We discuss the population genetic consequences of
mate availability and fecundity selection in the contexts of conserva
tion management of self-incompatible plant species and experimental in
vestigations on self-incompatibility in natural populations.