Large plant size counteracts early seed predation during the extended flowering season of a Silene uniflora (Caryophyllaceae) population

Abstract

A population of the alvar race of the perennial herb, Silene uniflora (Caryophyllaceae), which grows on thin soils in open alvar habitats on the Baltic island of Oland SE Sweden, was found to have an extended and more or less bimodal flowering phenology Large individuals produced flowers during both periods, while small, and presumably young, individuals only produced flowers in either of the two periods, or in part of both In the early flowering period plants were heavily infested by the seed‐predatory larvae of a noctuid moth, Hadena confusa, but in the late flowering period only a small proportion of the fruits was attacked by the seed predators The proportion of flowers developing into fruits was consistently high throughout the season Both the number of seeds per capsule and the mass of seeds decreased over the flowering season However, the germination success of early and late seeds did not differ Thus, although differing in number of seeds, both early and late flowers contributed to individual reproductive success Large individuals started to flower early in the season and despite their high loss of seeds in the early part of the summer they contributed a larger number of seeds to the seed pool than smaller and later‐flowering individuals Although selection was acting to favour later flowering during a year with high early seed predation, consistency of date of flower initiation and of relative predation impact on individuals across years was low suggesting that recurrent selection by seed predators is weak Seed predation, although heavy, is therefore judged to be unlikely to cause a significant evolutionary response on flowering phenology in this plant

Time after time: flowering phenology and biotic interactions

“…Most field surveys compare temporal variation in the intensity of seed and flower predation and flowering phenology to infer the direction of selection acting on phenology. Most studies found that flowering off-peak (either early [23,[34][35][36][37], or late [11,[38][39][40][41]) is associated with reduced seed predation, probably because fewer herbivores are present at those times. Similar effects are highlighted by studies indicating highest seed predation during peak flowering [42][43][44], especially when peak flowering attracts more seed predators owing to a higher density of flowers and fruits ( [28], J.A.…”

Local differentiation of flowering phenology in an alpine-snowbed herb Gentiana nipponica

“…Several studies demonstrated a size-dependent variation in flowering phenology (Pettersson 1994;Ollerton and Lack 1998;Sandring et al 2007). Total flower number within inflorescences significantly correlated with the timing of first flowering in G. nipponica.…”

Morphometric variation in a hybrid zone between the weed,Silene vulgaris,and the endemic,Silene uniflorassp.petraea(Caryophyllaceae), on the Baltic island of Öland

“…In addition, predation by Hadena moths may remove the majority of the capsules produced by S. uniflora ssp. petraea during the early part of the flowering season (Pettersson 1994;H.C. Prentice, unpublished data).…”