6533b839fe1ef96bd12a59ef

RESEARCH PRODUCT

Reproductive success ofDactylorhiza incarnatassp.incarnata(Orchidaceae): the effects of population size and plant visibility

subject

description

Reproduction of plants pollinated solely by flower-visiting animals depends on the ability of the population and each of its flowering member to attract pollinators. Factors affecting the pollination of nectarless species differ somewhat from those affecting the pollination of rewarding species due to the avoidance behaviour of pollinators after visiting empty flowers. We studied a non-mimic food-deceptive orchid, Dactylorhiza incarnata ssp. incarnata, in 16 populations in central Finland to examine if population properties and plant size affected reproductive success of plants. We found that the number of flowering plants increased total pollinia removal and seed production of the population, but had no effect on reproduction of individual plants. Dactylorhiza incarnata occurred in open mires with virtually no rewarding species in the neighbourhood, but the distance from the forest edge did not have any effect on reproduction. However, increased variation in the number of flowers among within-population plants enhanced plant reproductive success. The increased variation probably hampered the learning process of flower visitors. Plant size affected reproductive success only in populations with a high general reproductive success indicating that in the rarely visited populations, pollination of individual plants is mainly affected by random effects. For plants species that in their reproduction fully rely on the behaviour of their pollinators, visibility is a key issue. First, populations must be detected by the flower-visiting animals, and secondly, an individual plant must be capable of attracting suitable visitors. Many different factors affect the behaviour of pollinators and probability of successful pollination of plants. These factors affecting pollination success include competition between co-flowering species and within-species competition for visitor attention (Goulson 1999). Furthermore plants must be able to attract visitors to enter their flowers to ensure pollen removal and deposition. The positive effects of both density of flowering plants and plant visibility have been found e.g. in fooddeceptive orchid species, Dactylorhiza sambucina (Kropf and Renner 2005).