Sequential variation in the components of reproductive success in the distylousJasminum fruticans (Oleaceae) |
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Authors: | John D Thompson Bertrand Dommée |
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Institution: | (1) Centre d'Ecologie Fonctionelle et Evolutive, C.N.R.S., Route de Mende, B.P. 5051, 34033 Montpellier Cedex, France |
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Abstract: | A 2-year study of three natural populations of the distylousJasminum fruticans showed that mean fruit and seed production were significantly greater in shortstyled plants (thrums) than in long-styled
plants (pins). In this study, we investigated the role of four sequential factors which may differentially influence fruit
and seed set in the two floral morphs: (1) differences in flowering phenology, (2) a limitation of pollen transfer towards
pins, (3) a differential capacity of the two morphs to act through famale and male function and (4) differential fruit abortion
in the two morphs. Fruit set was significantly influenced by differences in flowering phenology although there were no differences
in flowering time between the two morphs. supplementary pollinations in a natural population significantly increased fruit
set and reduced the difference in fruit set between the two morphs in relation to controls, indicating a limitation on pollen
transfer which was most severe towards pin stigmas. In reciprocal crosses, seed set was significantly dependent on the paternal
and maternal identity of the pin parent. There was no significant variation among thrums for their performance as male or
female parent. Furthermore, individual pin plants with relatively high percentage seed set as female parents gave poor seed
set as male parents and vice-versa. Whereas fruit removal had no effect on seed number in thrum plants, a greater proportion
of viable seeds were produced on pin plants which were left to naturally mature their fruits than on pins which had fruits
artificially removed, suggesting the occurrence of selective fruit abortion in pins but not in thrums. The initially greater
maternal fitness of thrums due to their greater success as pollen recipients may thus be opposed by increased viable seed
set in the pins due to factors acting after the pollination stage. The relative reproductive success of floral morphs in the
distylousJ. fruticans is thus differentially influenced by ecological factors occurring at different stages of the reproductive process. |
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Keywords: | Distyly Phenology Reproductive success Jasminum Pollination |
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