Abstract
BackgroundFloral traits within plants can vary with flower position or flowering time. Within an inflorescence, sexual allocation of early produced basal flowers is often female-biased while later produced distal flowers are male-biased. Such temporal adjustment of floral resource has been considered one of the potential advantages of modularity (regarding a flower as a module) in hermaphrodites. However, flowers are under constraints of independent evolution of a given trait. To understand flower diversification within inflorescences, here we examine variation and covariation in floral traits within racemes at the individual and the maternal family level respectively in an alpine herb Aconitum gymnandrum (Ranunculaceae).ResultsWe found that floral traits varied significantly with flower position and among families, and position effects were family-specific. Most of the variance of floral traits was among individuals rather than among flowers within individuals or among families. Significant phenotypic correlations between traits were not affected by position, indicating trait integration under shared developmental regulation. In contrast, positive family-mean correlations in floral traits declined gradually from basal to distal flowers (nine significant correlations among floral traits in basal flowers and only three in distal flowers), showing position-specificity. Therefore, the pattern and magnitude of genetic correlations decreased with flower position.ConclusionsThis finding on covariation pattern in floral reproductive structures within racemes has not been revealed before, providing insights into temporal variation and position effects in floral traits within plants and the potential advantages of modularity in hermaphrodites.
Highlights
Floral traits within plants can vary with flower position or flowering time
We examine effects of flower position on floral traits and trait correlations in the herb, respectively at the individual level and at the maternal family level
Variation of floral traits with flower position and among families We examined the basal three, middle three and distal three flowers on each raceme in Aconitum gymnandrum
Summary
Floral traits within plants can vary with flower position or flowering time. Within an inflorescence, sexual allocation of early produced basal flowers is often female-biased while later produced distal flowers are male-biased. A common pattern observed in hermaphrodites is a reduction in the number or size of reproductive structures in sequentially blooming flowers [19,20] This intra-inflorescence variation in floral allocation has been attributed to the effects of resource competition [21,22,23], architectural effects [20,24,25] or mating environments [26,27]. The ability to adjust sex allocation over time is one potential advantage of modularity in hermaphrodites [26,28,29], there are few empirical studies that examine temporal variation in floral traits [30,31], considering trait correlations among sequentially blooming flowers
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