Male moths provide pollination benefits in the Silene latifolia–Hadena bicruris nursery pollination system

Abstract

Summary1. Evolutionary conflicts of interest underlie mutualisms, including plant ⁄ pollinator interactions. This is particularly evident in 'nursery pollination', in which the pollinators lay eggs inside the flowers and the offspring of the pollinator consume the developing seeds. Low benefit (pollination service) to cost (seed predation) ratios could destabilize such associations towards parasitism. 2. Although in most of the well-known cases pollen transfer is associated with oviposition, in some systems the males of the seed predator may contribute to pollination, affecting the strength and outcome of the interaction between the plant and their ovipositing pollinators. In addition, in dioecious species male and female plants differ in the direct costs of seed predation and benefits of attracting pollinators, which may lead to sex-specific strategies. 3. We investigated whether pollinator and plant sex affect pollination in the interaction between dioecious plant Silene latifolia and its nursery pollinator, Hadena bicruris (Noctuidae). 4. Data on visitation behaviour and pollination efficiency in experimental plant patches demonstrate that (i) male moths are equally efficient pollinators as female moths, leading to fruit initiation in around 80% of visits and to fertilization of around 45% of the ovules in one visit; (ii) female and male moths do not preferentially visit flowers of one sex; and (iii) feeding behaviour is sufficient to ensure pollen transfer. However, female moths visited significantly more flowers than male moths. 5. Altogether this suggests that both moth sexes provide a pollination benefit to the plant with no differences in pollination efficiency but that female moths, before seed predation costs are accounted for, seem to provide greater benefits owing to their increased activity. That male moths contribute to seed production likely decreases the plant's dependency on ovipositing moths for pollination.

Variable nursery pollinator importance and its effect on plant reproductive success

“…Fruit predation rates were *10% in 2005 and 30% of total fruits produced in 2006, which reflect the variable adult H. ecytpa populations observed in those 2 years. In another non-obligate system, H. bicruris lays its eggs on female plants of dioecious S. latifolia where each pistil has hundreds of ovules and the larvae also eat more than one fruit (but many fewer than H. ectypa) to complete their development (Labouche and Bernasconi 2010). Thus, our data indicate that in years like 2006 when pollinator service between copollinators and H. ectypa is equivalent, heavy larval seed predation turns the nursery pollination interaction negative.…”

The incidence and selection of multiple mating in plants

“…pollen carry-over versus sequential visits) been empirically determined [19,23,34,35]. These studies used a combination of pollinator observations (noting the time interval between visits, the time spent on each flower and the number of visited flowers) and manipulation of the pollen load on test flowers for which seed paternity [49] or the proportion of fertilized ovules were measured [20].…”

The effects of inbreeding, genetic dissimilarity and phenotype on male reproductive success in a dioecious plant

“…The species is dioecious with chromosomal sex determination [45]. Pollinators are mainly moths [46], including Hadena bicruris [47,48].…”