Describing the mating system of Halenia deflexa, a native New Brunswick plant

Abstract

The New Brunswick native plant Halenia deflexa (Gentianaceae) provides an excellent opportunity to investigate the association between within-plant variation in flower shape and within-plant variation in mating system. At the start of the season, H. deflexa flowers produced have long nectar spurs, but by the end of the season, nectar spur length declines significantly. This within-plant variation between early flowers and late produced flowers offers a character upon which natural selection could act. Nectar spurs offer a sugary reward to pollinators that then bring in outcross pollen for fertilization. Therefore, a decline in nectar spur length throughout the season could affect H. deflexa mating system. Halenia deflexa could be entirely self-incompatible, relying on outcrossing as its only mechanism for reproduction. On the other hand, H. deflexa could exclusively self or have a mixed mating system where both outcrossing and selfing are used. I compared plants with full pollinator access to pollinator excluded plants in bags to investigate this potential interaction between nectar spur and mating system. However, I observed no effect of pollinator access on H. deflexa fruit set or number of seeds per fruit throughout the season. I also compared emasculated flowers with anthers removed to intact flowers to observe the effects of autogamy on H. deflexa mating system. The ability to reproduce through autogamy increases fruit set throughout the season. Autogamous fruit produce more seeds than non-autogamous fruit early in the season, but by the end of the season there is no difference between the two. Collectively, my studies indicate that H. deflexa has a mixed mating system that does not rely on pollinators to successfully reproduce.