Cc. Daehler, VARIATION IN SELF-FERTILITY AND THE REPRODUCTIVE ADVANTAGE OF SELF-FERTILITY FOR AN INVADING PLANT (SPARTINA-ALTERNIFLORA), Evolutionary ecology, 12(5), 1998, pp. 553-568
The factors responsible for the reproductive success or failure of ind
ividuals in small, founding populations have received little attention
. Previous work on a small population of smooth cordgrass (Spartina al
terniflora) invading San Francisco Bay, California found that most clo
nes flower prolifically but set little or no seed, while a few clones
have high rates of viable seed sell producing most of the seeds in the
population. This study first identifies recruitment from seeds as the
main source of new smooth cordgrass plants during invasion and then t
ests the influence of growing conditions and pollination treatment on
viable seed set among clones established in San Francisco Bay. Field t
ransplants indicated that a clone's seed set rate was not strongly dep
endent on its site of establishment. Low and high nutrient greenhouse
treatments also had little effect on viable seed set rates within most
clones. In contrast, pollination treatment (self-pollination or outcr
ossing) had a major effect on viable seed set rates. Most clones had h
igh seed set rates after outcross-pollination, but clones varied widel
y in their selfing capacity. Zero or low viable self-seed set rates we
re most common; however, a few clones had high viable self-seed set ra
tes, comparable to outcross seed set rates. A clone's selfing capacity
was significantly correlated across years (r = 0.89, P < 0.001), and
capacity to set viable self-pollinated seeds in the greenhouse was sig
nificantly correlated with the clone's rate of viable seed set in the
field (r(s) = 0.74, P < 0.005). In this growing population where cross
-pollination is limited, only the clones with high selfing ability had
high viable seed set rates in the field. Among primarily outcrossing
plant invaders, variation in self-fertility among individuals may be a
common phenomenon, with important implications for genetic differenti
ation, effective population size and patterns of spatial spread during
an invasion.