Floral traits that increase attractiveness to pollinators are predicted to evolve through selection on male function rather than on female function. To determine the importance of male-biased selection in dioecious Wurmbea dioica, we examined sexual dimorphism in flower size and number and the effects of these traits on pollinator visitation and reproductive success of male and female plants. Males produced more and larger flowers than did females. Bees and butterflies responded to this dimorphism and visited males more frequently than females, although flies did not differentiate between the sexes. Within sexes, insect pollinators made more visits to and visited more flowers on plants with many flowers. However, visits per flower did not vary with flower number, indicating that visitation was proportional to the number of flowers per plant. When flower number was experimentally held constant, visitation increased with flower size under sunny but not overcast conditions. Flower size but not number affected pollen removal per flower in males and deposition in females. In males, pollen removal increased with flower size 3 days after flowers opened, but not after 6 days when 98% of pollen was removed. Males with larger flowers therefore, may have higher fitness not because pollen removal is more complete, but because pollen is removed more rapidly providing opportunities to pre-empt ovules. In females, pollen deposition increased with flower size 3 days but not 6 days after flowers opened. At both times, deposition exceeded ovule production by four-fold or more, and for 2 years seed production was not limited by pollen. Flower size had no effect on seed production per plant and was negatively related to percent seed set, implying a tradeoff between allocation to attraction and reproductive success. This indicates that larger flower size in females is unlikely to increase fitness. In both sexes, gamete production was positively correlated with flower size. In males, greater pollen production would increase the advantage of large flowers, but in females more ovules may represent a resource cost. Selection to increase flower size and number in W. dioica has probably occurred through male rather than female function.

Summary 0We examined the sources and consequences of seed mass variation in Banksia marginata occurring in _re!prone heath on nutrient!poor soils to determine factors in~uencing seed size and possible _tness bene_ts of large seeds[ 1 Individual seed mass varied _vefold[ Variation occurred among populations "18) of total#\ among years "09)# and among plants "plants\ 5)^year × plants\ 02)#\ but was most pronounced within plants "31)#[ Within plants\ seed mass variation was greater within infructescences "24)# than among infructescences "6)#[ 2 Seed mass variation within infructescences was not related to whether follicles contained one or two seeds[ Seed mass was also una}ected by ovule position within follicles and follicle position within infructescences[ 3 Seed mass variation among infructescences and plants was related to the limited availability of nutrient resources during seed provisioning[ Mean seed mass was negatively related to seed number per infructescence and per plant[ When resources decreased late in the~owering season and after defoliation\ seed mass declined by 6Ð 09) and seed number by 20Ð34)[ When resources increased after in~orescence removal\ seed mass increased by 7) but seed number was una}ected[ Plants thus had only a limited capacity to maintain seed mass by adjusting seed number when resources varied[ 4 The N and P contents of seeds "mg seed −0 # increased linearly with seed mass\ indicating costs of producing larger seeds in terms of limited environmental nutrients[ 5 Seedling size increased with seed mass\ implying _tness bene_ts of larger seeds in terms of increased seedling establishment on nutrient!poor soils[ Seed mass had little or no e}ect on seed germination\ relative growth rates and root]shoot ratios[ 6 Although stabilizing selection should eliminate seed mass variation occurring within plants\ such variation persists because resource constraints limit the ability of plants to control individual seed size[ Keywords] nutrient allocation patterns\ nutrient!poor soils\ seed nutrient content\ seed size and number\ seedlings Journal of Ecology "0887# 75\ 452Ð462

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In self-incompatible plants, interference by self pollen or genetically related pollen can potentially exacerbate pollen limitation, although this has rarely been demonstrated. We examined the breeding system, pollen limitation, and pollen interference using self- and cross- pollinations and pollen supplementations in Burchardia umbellata, an insect-pollinated lilioid monocot. Ovule fertilization and seed set were less following selfing than crossing (22 vs. 78% and 4 vs. 73%, respectively), indicating partial self-incompatibility. Flowers were partially protandrous, and flowers opened concurrently on plants potentially allowing self pollen interference. Natural seed set was pollen limited and varied within and among years, probably due to variation in flowering plant density. Interference by self or genetically related pollen caused pollen limitation as evidenced by increased seed set of bagged cross-pollinated plants compared to unbagged pollen-supplemented plants in two years. In 1996, both fertilization and seed set increased in response to cross-pollination, indicating that interference occurred in the style and ovary. In 1997, only seed set increased after cross-pollination indicating that interference occurred in the ovary. Inappropriate pollen deposition may contribute to pollen limitation more often than previously recognized and should select for floral traits that decrease deposition of self or related pollen.