SELECTION ON REPRODUCTIVE CHARACTERS - FLORAL MORPHOLOGY IN ASCLEPIAS-SYRIACA

Pollinia insertions and removals represent a convenient index of male and female fertilities in the Asclepiadaceae. This fact, in conjunctio n with regression analysis, allows estimation and comparison of gender -specific selection acting on floral characters in Asclepias syriaca. Univariate regression analysis indicates statistically significant sel ection on minute aspects of floral morphology through the male and esp ecially female reproductive pathways. Analyses using multiple regressi on to correct for overall plant size do not qualitatively change the u nivariate results. The relatively large number of statistically signif icant selection gradients suggests active adaptation of floral morphol ogical features to the pollinator fauna. Selection through female func tion differs significantly from selection on the same trait through ma le function for four traits, emphasizing an antagonism between genders in hermaphrodites. This antagonism and the absence of selection of th e antagonistic traits through net fertility are consistent with an equ ilibrium quantitative genetic perspective, while greater opportunity f or selection through female function is counter to expectations based on Bateman's principle of sexual selection.