Heritabilities of lateral and vertical herkogamy in Lysimachia arvensis

Herkogamy, spatial separation between stigma and anthers within a flower, is important in regulating plant‐mating systems. We studied phenotypic variation and heritability of herkogamy traits in Lysimachia arvensis (= Anagallis arvensis ) that show both lateral and vertical herkogamy in the same flower, a rare strategy in flowering plants. Both lateral and vertical herkogamy showed continuous variation in 15 natural populations. Lateral herkogamy, measured as the angle between style and stamens, ranged from 5.6 to 66.5°; vertical herkogamy ranged from reverse to approach herkogamy. Herkogamy traits were constant within plants but variable among plants and populations. Flowers with marked lateral herkogamy showed mainly reverse herkogamy, whereas flowers with low lateral herkogamy showed mainly approach herkogamy. Both herkogamy traits showed a high degree of narrow sense heritability (h 2 = 0.843 for lateral and h 2 = 0.635 for vertical herkogamy). We discuss the possibility that variation in both herkogamy traits among populations of L. arvensis is a consequence of differential selective pressures under different pollination environments.