Effects of Flower Number and Position on Self-Fertilization in Experimental Populations of Eichhornia paniculata (Pontederiaceae)

Barrett, Spencer C. H.; Harder, Lawrence D.; Cole, William W.

doi:10.2307/2390078

Cited by 105 publications

(117 citation statements)

References 47 publications

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“…Recently, researchers have begun to investigate the effects of floral variation on individual outcrossing rates within a population (Barrett et al, 1994;Brunet and Eckert, 1998;Vrieling et al, 1999;Motten and Stone, 2000). Current procedures for estimating population-level outcrossing rates are quite robust if multiple loci are included in the study (Ritland and Jain, 1981).…”

Section: Methodsmentioning

confidence: 99%

Effect of variation in herkogamy on outcrossing within a population of Gilia achilleifolia

2005

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The diverse features of floral morphology are often thought to be well-designed mechanisms to manipulate plant mating systems. We evaluated the effectiveness of one such mechanism, anther-stigma separation (herkogamy), in controlling variation in the level of outcrossing among plants in a population of Gilia achilleifolia. Variation in outcrossing rates within populations has the potential to influence the coevolution between inbreeding depression and mating system. Using four polymorphic allozymes, we compared the outcrossing-rate estimates of two groups of individuals under natural conditions: one group with low herkogamy and another with high herkogamy. The high herkogamy group had a higher outcrossing rate (0.572) than the low herkogamy group (0.335). This suggests that the withinpopulation variation in outcrossing rate could potentially cause the previously observed association between herkogamy and inbreeding depression (Takebayashi and Delph, 2000). A previous study of floral traits among G. achilleifolia populations failed to detect a relationship between herkogamy and outcrossing rate, demonstrating that the functionality of traits may be obscured in amongpopulation studies as a consequence of uncontrolled environmental variation. Additionally, the effect of herkogamy on outcrossing rate in delayed selfers such as G. achilleifolia may be particularly prominent when pollinator availability is low. Our population-level estimate of outcrossing rate (0.444) was somewhat lower than an estimate from the same population, 15 years prior to our study (0.75), suggesting that pollinator availability may fluctuate among years. Both within-year and among-year variation in the outcrossing rate may have a strong influence on matingsystem evolution.

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Section: Methodsmentioning

confidence: 99%

Effect of variation in herkogamy on outcrossing within a population of Gilia achilleifolia

2005

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“…Crawford, 1984;Schoen and Lloyd, 1992;LeClerc-Potvin and Ritland, 1994), few studies have tested this assertion (Barrett et al, 1994;Harder and Barrett, 1995;Snow et al, 1996). Harder and Barrett (1995) established experimental arrays of Eichhornia paniculata with all pairwise combinations of four floral display sizes (three, six, nine, or 12 flowers).…”

Section: Jd Karron Et Almentioning

confidence: 99%

“…In self-compatible species, pollen load composition may affect plant-mating system phenotypes and the evolutionary stability of mixed mating systems (Holsinger, 1991;Lloyd, 1992). However, surprisingly little is known about the relationship between patterns of pollinator movement and the realized mating system of flowering plants (Barrett et al, 1994;Harder and Barrett, 1996;Holsinger, 1996;Snow et al, 1996, Eckert, 2000.…”

Section: Introductionmentioning

confidence: 99%

The influence of floral display size on selfing rates in Mimulus ringens

et al. 2003

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Pollinators often visit several flowers in sequence on plants with large floral displays. This foraging pattern is expected to influence the rate of self-fertilization in self-compatible taxa. To quantify the effects of daily floral display on pollinator movements and selfing, we experimentally manipulated flower number in four replicate (cloned) arrays of Mimulus ringens (Scrophulariaceae), each consisting of genets with unique combinations of homozygous marker genotypes. Four display classes (two, four, eight and 16 flowers) were present in each array. Pollinator visitation rate per flower and seed set per fruit were unaffected by display. However, flower number strongly influenced the frequency of withinplant pollinator movements, which increased from 13.8% of probes on two-flower displays to 77.6% of probes on 16-flower displays. The proportion of within-plant movements was significantly correlated with selfing (r ¼ 0.993). The increase from 22.9% selfing on two-flower displays to 37.3% selfing on 16-flower displays reflects changes in the extent of geitonogamous self-pollination. We estimate that approximately half of all selfing on 16-flower displays resulted from geitonogamy. Selfing also varied dramatically among fruits within display classes. Nested ANOVA indicates that differences among flowers on two-flower ramets accounted for 45.4% of the variation in selfing, differences among genets accounted for 16.1% of the variation, and statistical and sampling error accounted for 38.5% of the variation. Differences among flowers within ramets may reflect the order of sequential floral probes on a display.

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“…However, mating-system variation has only rarely been examined at this level (Motten & Antonovics 1992;Barrett, Harder & Cole 1994;Cruzan et al 1994). For instance, sequential flowering in dichogamous species is expected to cause predictable amongflower variation in the outcrossing rate (Brunet & Charlesworth 1995).…”

Section: Outcrossing In Blue Columbinementioning

confidence: 99%

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

1998

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The hermaphrodite sexual system possessed by most flowering plants creates the potential for close inbreeding through self-pollination. While many species strongly limit self-fertilization with self-incompatibility, about one-third of hermaphrodite taxa are selfcompatible (Richards 1986) and the balance between outcrossing and self-fertilization will depend, in part, on the relative deposition of self-and cross-pollen on stigmas (Holsinger 1992). This, in turn, can be influenced by both intrinsic and extrinsic factors, especially features of floral morphology and display.Floral features, such as the spatial and temporal separation of male and female functions within flowers (herkogamy and dichogamy, respectively), are generally expected to promote outcrossing, either through reducing within-flower selfing (autogamy, e.g. Darwin 1876;Müller 1883;Proctor & Yeo 1973;Faegri & van der Pijl 1979;Richards 1986) or betweenflower selfing (geitonogamy; Holsinger 1996). Aspects of floral display are also expected to influence the level of outcrossing. Both flower size and display size may enhance opportunities for outcrossing by increasing pollinator visitation Summary 1. The effect of variation in floral morphology and display on the level of outcrossing was investigated in a Rocky Mountain population of the self-compatible, protandrous, perennial herb, Aquilegia caerulea. ANOVA revealed substantial variation among 36 plants in floral traits including herkogamy (CV = 35%), protandry (23%), pollen production (12%), flower size (8%), the daily number of flowers in male phase (58%) and autofertility, seed production in the absence of pollinators (192%). 2. Whether this floral variation affected the outcrossing rates of individual plants was assessed using both a categorical analysis, in which outcrossing rates were estimated separately for groups of plants that differed with respect to floral features, and a correlation analysis involving outcrossing rates estimated for individual plants from large progeny arrays (n ≥ 40). Both analyses indicated significant positive correlations between the outcrossing rate and herkogamy (r = + 0·71) and protandry (+ 0·54), negative correlations with the number of flowers in male phase during each day of female phase (-0·42) and autofertility (-0·36), but no correlation with flower size or pollen production. 3. Partial correlation indicated that both herkogamy and dichogamy, although weakly intercorrelated, were positively correlated with the outcrossing rate and that these effects were only partly mediated by their negative correlation with autofertility. 4. The extent to which floral features and the outcrossing rate covaried across the flowering sequence within plants was also examined in this study. As expected for a plant with strong protandry and sequential blooming, the number of flowers in male phase decreased strongly with flowering sequence position. However, categorical analysis did not support the prediction that the first flowers to open on an inflorescence outcrossed at a low...

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Effects of Flower Number and Position on Self-Fertilization in Experimental Populations of Eichhornia paniculata (Pontederiaceae)

Cited by 105 publications

References 47 publications

Effect of variation in herkogamy on outcrossing within a population of Gilia achilleifolia

Effect of variation in herkogamy on outcrossing within a population of Gilia achilleifolia

The influence of floral display size on selfing rates in Mimulus ringens

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

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