Functional significance of petals as landing sites in fungus‐gnat pollinated flowers of Mitella pauciflora (Saxifragaceae)

Abstract

Summary Despite the well‐known visual attraction function of angiosperm petals, additional roles of these floral organs (e.g. the provision of landing‐site platforms for pollinators) have rarely been examined. This is likely because most petals perform multiple functions, making it difficult to isolate the importance of landing sites in pollination success. We investigated the landing‐site function of dull‐coloured pinnately branched petals in Mitella pauciflora flowers, which are predominantly pollinated by fungus gnats. We conducted a field experiment, in which the effects of experimental petal removal on pollinators’ approach, landing and visit duration and floral reproductive success were examined in naturally pollinated flowers. According to direct and time‐lapse camera observations, petal removal did not influence pollinators’ approach frequency or visit duration, but did significantly decrease their landings. Fruit set and pollen dispatch both significantly decreased with petal removal, indicating that petals promote female and male reproductive success in M. pauciflora by facilitating pollinator landing. This demonstrates that inconspicuous petals primarily have a landing‐site function rather than a visual attraction function in M. pauciflora. Discriminating between diverse petal functions is a challenging problem, and new approaches are required to elucidate the functional features of angiosperm flowers. A http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.12842/suppinfo is available for this article.

Diversity, Daily Activity Patterns, and Pollination Effectiveness of the Insects Visiting Camellia osmantha, C. vietnamensis, and C. oleifera in South China

“…Similarly, C. vietnamensis produces larger flowers than the other Camellia species (Table 4), but was not visited more often by any flower visitor species. Usually, larger displays of flowers/inflorescences release more floral scents and are more visible than smaller displays, attracting more visiting insects [29]. This may be explained by the theory that floral and inflorescence traits evolved under a trade-off between visual and olfactory cues [30].…”

Relative contributions of neutral and non-neutral processes to clinal variation in calyx lobe length in the series Sakawanum (Asarum: Aristolochiaceae)

“…Considering that divergent selection is detected in calyx lobe lengths in the series Sakawanum, these extended flower organs could have -6000 -6200 -6400 -6600 -6800 -7000 -7200 -7400 -7600 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 K important roles (e.g. visual attraction, landing foothold for pollinators, and emitting olfactory attractants), as suggested for other flowers with elongated organs (Policha et al, 2016;Katsuhara et al, 2017). We could hypothesize that the variation of calyx lobes in the series Sakawanum is related to pollinator attraction, although other biotic and abiotic factors may also have affected calyx lobe length.…”

Pollination by fungus gnats and associated floral characteristics in five families of the Japanese flora

“…A study conducted by Tremblay and Ackerman (2007) showed that there is no difference in reproductive success between unicolour (yellow) and bicolour (yellow and dark red) variants of fungus gnat-pollinated Lepanthes rupestris, suggesting that dark red pigmentation does not increase floral attractiveness. A recent study by Katsuhara et al (2017) found that the dark red, branched petals of fungus gnat-pollinated Mitella pauciflora do not function as attractants, but rather as footholds. Although it is possible that dark colour is mimetic of fungus gnat oviposition sites (e.g.…”

“…Unlike floral colour, floral scent is hypothesized to play a critical role in fungus gnat-pollination systems (Vogel and Martens, 2000;Okamoto et al, 2015;Katsuhara et al, 2017). For example, some plants pollinated by fungus gnats (Arisaema, Corybas and Heterotropa) are thought to employ brood site mimicry because they produce a mushroom-like scent and the eggs and larvae of fungus gnats have been observed inside their flowers [Sugawara, 1988;Vogel and Martens, 2000;Kelly et al, 2013;Woodcock et al, 2014;but Kelly and Gaskett (2014) and Kuiter and Findlater-Smith (2017) refuted fungal mimicry in Corybas].…”