The Shape of the Female Fitness Curve for Cynoglossum officinale: Quantifying Seed Dispersal and Seedling Survival in the Field

Abstract

When hermaphroditic plants shift their sex allocation to produce more seeds and less pollen, it is frequently assumed that the female component of fitness is strictly proportional to the number of seeds produced. However, if producing more seeds results in more competition between seedlings, the female fitness gain curve levels off with high investments in seeds. The shape of this curve is relevant for sex allocation theory, but rarely have data been collected. For Cynoglossum officinale we described the relationship between the number of seeds produced on the mother plant and the number and weight of seedlings in September of the following year. As expected, around large plants of C. officinale more seedlings were retrieved after the germination period in March. The seedlings of large plants were dispersed over an area similar to that of small plants. As a result, seedlings around large plants had a significantly higher chance to have a neighbouring sibling within one dm². Survival and growth of single or grouped (density > 2) seedlings did not differ significantly. As a result, total dry weight of seedlings in September was a linear function of the number of seeds on the parent plant. Our data indicate a linear female fitness gain curve.

Key words

Female fitness - local resource competition - seed dispersal - germination and survival - sex allocation