Abstract
ABSTRACT Most flowering plants are visited by various pollinator insects. To understand floral specialization for pollinators, the relative importance of different flower visitors to the focal plant species should be revealed. In the present study, we observed the insects that visited the orchid Platanthera hologlottis throughout the day and night using interval timer photography to reveal the relative importance of diurnal and nocturnal flower visitors. We observed visitation by both diurnal (e.g. the butterfly Ochlodes ochraceus) and nocturnal (e.g. the moth Thysanoplusia intermixta) insects and examined their relative contribution to fruit production and pollinarium removal experimentally. Results showed that the fitness was higher in flowers visited by nocturnal insects than in those visited by diurnal insects. These results suggest that the floral traits of P. hologlottis may be specialized for nocturnal flower visitors rather than diurnal flower visitors.
Highlights
We revealed the insect visitors to flowers of P. hologlottis using interval photography
Visitation by Thysanoplusia intermixta, which was considered to be a principle pollinator of P. hologlottis by Inoue (1983), was observed at all times during the day and night
Our results indicated that T. intermixta does not pollinate P. hologlottis because only nocturnal flower visitors can influence the fitness of P. hologlottis
Summary
Most flowering plants depend on animals, mostly insects, for their pollination (Ollerton et al 2011). The relationship between plants and pollinator insects (i.e. pollination mutualism) strongly influences their reproductive success. Floral traits can become ecologically, evolutionary, and phenotypically specialized for their pollinators (Boberg and Ågren 2009; Newman et al 2015; Armbruster 2017). Sletvold et al (2012) reported that diurnal pollinators mediated stronger selection on traits influencing floral display than nocturnal pollinators and that this selection varied between populations of Gymnadenia conopsea. These studies showed that different pollinator species exerted different selection pressures on floral traits. To understand floral specialization, it is important to reveal the pollinator species that exert selection pressure on the plant species under investigation
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