Within-population variation in the relation between node number and flowering time in Rhinanthus angustifolius (Orobanchaceae)

Background and aims – The annual hemiparasitic plant genus Rhinanthus displays large variation in the date of onset of flowering, and ecotypes have been described from populations with different flowering times. Much less is known, however, about the variation in flowering time within populations of an ecotype, which is important for the adaptive capacity of a population. The number of nodes produced before the first flower is an important trait linked to flowering time differences among populations, and this trait and its relation with flowering date were investigated. Methods – Seeds from a natural, early-flowering population of Rhinanthus angustifolius, mown in early July, were used to establish a new field population in 2003, mown after summer, and to cultivate plants in the greenhouse in 2001 and 2004. The onset of flowering, node number and plant size were recorded in the field population in 2005 and in 2008. In the greenhouse, germination date, node number and flowering date were recorded. Key results – Flowering time was strongly correlated with node number in all years: the production of more nodes before the first flower was associated with a delay in flowering. There was always considerable variation around the median flowering date among plants with the same number of nodes, even in the greenhouse. Removing variation in the timing of germination in the greenhouse experiment did not reduce variation in flowering date. Part of the remaining variation was due to variation in plant size: larger plants flowered earlier. After five years, the relaxed selection on flowering time by mowing later had increased node number and delayed flowering in the new field population. Conclusions – Both genetically determined (node number) and phenotypically plastic (plant size) traits contribute to variation in flowering time within populations, and even under strong selection against late flowering, wild populations may harbour enough variation to react to a decrease in this selection pressure by later mowing

Wesselingh_2019_Rhinanthus_hybrids_greenhouse_flowers

flower production of plants in the greenhouse in 201

Wesselingh_2019_Rhinanthus_hybrids_field_flowers_seeds

field transplant: flower and seed production of surviving plant

Wesselingh_2019_Rhinanthus_hybrids_greenhouse_2014_flowers

flower production by plants in the greenhouse in 201

The biology of non-weedy parasitic plants: the third symposium

The biology of non-weedy parasitic plants: the third symposiu

Wesselingh_2019_Rhinanthus_hybrids_field_emergence_survival

results of field transplant experiment: emergence of seedlings and survival until flowerin

Performance of two Rhinanthus species under different hydric conditions

Rhinanthus angustifolius and Rhinanthus minor are annual hemiparasitic herbs found in open vegetations. They are closely related, hybridize frequently, and appear to have largely overlapping niches, although some floras report a preference of R. angustifolius for more humid conditions compared to R. minor. We analysed the relative fitness of both species by following their fate from germination to seed production in three different hydric treatments (wet, moist and dry) in a garden experiment. We found that R. angustifolius was either as fit as or fitter than R. minor in all conditions and for all studied parameters, with a slightly higher flower production in R. angustifolius in the wet treatment. Wet conditions had a negative effect on germination and flowering rate, but they increased flower and seed production. These observations show that environmental conditions will influence the composition of mixed Rhinanthus populations