Male Reproductive Success and Variation in Fruit and Seed Set in Aquilegia Caerulea (Ranunculaceae)

Abstract

The timing of fruit initiation and the proximity of fruits to resources influence the probability of fruit and seed initiation in many hermaphroditic plants. In two populations of Aquilegia caerulea, both fruit and seed set decreased significantly between early and late flowers. Low fruit and seed set of late flowers was not due to pollen limitation. Fruit and seed set of late flowers remained low when extra pollen was added to these flowers (pollen quantity), or when all flowers on an inflorescence received self or outcross pollen (pollen quality). While competition for resources occurred among flowers, resource limitation was not responsible for the low fruit and seed set of late flowers. Indeed, preventing pollination of late flowers significantly increased both fruit and seed set of early flowers, but fruit and seed set of late flowers remained low when early flowers were prevented from setting fruits. Late flowers were not just smaller or larger replicates of early flowers, as they allocated more reproductive resources to male function relative to early flowers. Neither herbivory nor architectural constraints could explain the low fruit and seed set of late flowers. While previously published adaptive explanations proposed to explain the low fruit and seed set of late flowers have emphasized a positive aspect to female reproductive success, it is suggested here that both male and female functions should be considered. Morphological data and estimates of male and female reproductive success demonstrate how, both morphologically and functionally, late flowers on inflorescences of A. caerulea specialize as males, early flowers as females. It will be argued that protandry in this sequential bloomer is expected to select for an increase in relative male allocation between early and late flowers, and that the observed pattern of resource allocation and the decrease in fruit and seed set between early and late flowers is consistent with this prediction.

Comparative Study in Seed Yield and Flowers Attractivity to Bee Visitors Between Nigella Sativa L. and Nigella Damascena L. (Ranunculaceae) Grown Under Semiarid Conditions

“…The increased seed numbers in open pollinated flowers resulted in the highest total seeds weight than other treatments in both species. Similar results have been obtained with many other species (Holtsford, 1985; Devlin, 1989;Karoly, 1992;Brunet, 1996). In summary, both N. sativa and N. damascena are adapted to grow under semiarid conditions with different productivity rate and were visited by a diversity of insect pollinators.…”

“…Seed-set success is influenced not only by pollination success but also by post-pollination processes such as pollen germination activity, pollen tube growth, and development of fertilized seeds (Stephenson, 1981;Lee, 1988). Variations in the quality of pollen received by flowers have been related to directional movement of pollinators, to the order of development of flowers, (Wyatt, 1982;Nilsson, 1983;Berry and Calvo, 1991;Brunet and Charlesworth, 1995;Brunet, 1996) and to insufficient pollen receipt (Lee, 1988;Berry and Calvo, 1991;Brunet and Chalesworth, 1995). Total seed weight was greatly affected by Nigella species and treatments at (P ≤ 0.05).…”

Effects of floral morphology and display on outcrossing in Blue Columbine, Aquilegia caerulea (Ranunculaceae)

“…There was also negative, but non-significant correlations between number of seeds/ovule and both herkogamy (r = -0·21, n = 30, P < 0·28) and individual outcrossing rate (r = -0·24, n = 19, P < 0·33). However, a pollen addition experiment conducted on other plants in this population during the same year as this study did not provide any evidence that seed production was generally limited by pollen availability that year (Brunet 1996).…”

“…This study was conducted in a population of A. caerulea located about 3·5 km north-west of Gothic, CO, USA (elevation 3030 m; Bellview population in Brunet 1996). In this area, A. caerulea grows on dry mountain slopes under intense sunlight.…”

Offspring Quality in Relation to Excess Flowers in Pultenaea Gunnii (Fabaceae)

“…Other female fitness advantages of nonfruiting flowers could still be at work, but these mechanisms have not been well studied, particularly mechanisms involving variation in resource environment among years. Empirical evidence from other species in favor of a primarily male function of nonfruiting flowers remains strong (Brunet 1996;Queller 1997;Vaughton and Ramsey 1998), although consistent sex-specific selection on attractive traits in general may be relatively uncommon (Ashman and Morgan 2004).…”