DoesTraunsteinera globosa(the globe orchid) dupe its pollinators through generalized food deception or mimicry?

Abstract

Non‐rewarding orchids rely on various ruses to attract their pollinators. One of the most common is for them to resemble flowers sought by insects as food sources. This can range from generalized food deception to the mimicry of specific sympatric food plants. We investigated the basis of pollinator deception in the European food‐deceptive orchid Traunsteinera globosa, which has unusually compact flowerheads resembling those of sympatric rewarding species of Knautia and Scabiosa (Dipsacaceae), and Valeriana (Caprifoliaceae). Visual signals of T. globosa are similar in both fly and bee vision models to those of the sympatric food plants used in the choice experiments, but scent signals are divergent. Field experiments conducted in Austria and the Czech Republic showed that both naive and experienced (with respect to visitation of T. globosa) insect species approached the orchids at the same rate as food plants, but direct contact with orchid flowers was taxon specific. Flies were most easily duped into probing the orchid, and, in doing so, frequently received and deposited pollinaria, whereas most bees and butterflies avoided landing on orchid flowers. We conclude that T. globosa is a mimic of a guild of fly‐pollinated plants, but the ecological dependence of the orchid on its models remains to be fully tested. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2016, 180, 269–294.

Masquerading as pea plants: behavioural and morphological evidence for mimicry of multiple models in an Australian orchid

“…While pollination via mimicry of flowering plants usually involves a particular model species, there is evidence that some plants mimic a guild of plant species rather than a specific model (Jersáková et al, 2016). Plant guilds are recognized by both sharing a particular pollinator (or group of related pollinators) and having very similar floral traits (Manning and Goldblatt, 1996), which are likely to represent adaptations to the particular pollinator(s) (Johnson, 2010).…”

“…However, in orchids there is some evidence for guild mimicry, where a rewardless species mimics a range of model species that have similar floral traits and share the same pollinator species (Brown and Brown, 1979;Dafni and Bernhardt, 1990;Johnson and Schiestl, 2016). For example, the European orchid Traunsteinera globosa attracts pollinators by mimicking the colour and inflorescence shape of representatives of three morphologically similar co-occurring genera in the Dipsacaceae and Caprifoliaceae (Juillet et al, 2007;Jersáková et al, 2016). This strategy may be advantageous over other more specialized forms of Batesian mimicry as the mimic may receive a fitness benefit from co-flowering with a wider range of model plants.…”

Changing How Biologists View Flowers—Color as a Perception Not a Trait

“…However, other cues are available to pollinators when making choices on visiting flowers. For example, there may be differences in color pattern that could inform foraging decisions, particularly if there is a variable model or multiple model species (e.g., Jersáková et al, 2016;Scaccabarozzi et al, 2018). Outside of color, floral odor (Leonard et al, 2011) and morphology (Howard et al, 2018) are used as cues to identify suitable food sources, and corolla shape has shown to be important for successful mimicry of flowers (Jersáková et al, 2012).…”

“…Rejection of this null hypothesis would suggest that perception prevents the generalization of conclusions based on purely physical aspects of color signals. A biological system for testing this hypothesis is that of deceptive orchids where a non-rewarding species closely resemble a rewarding flower (Peter and Johnson, 2008;Jersáková et al, 2016). In this scenario, resemblance between mimic and model should be close enough that pollinators are sometimes unable to reliably discriminate between them (Jersáková et al, 2016).…”

“…A biological system for testing this hypothesis is that of deceptive orchids where a non-rewarding species closely resemble a rewarding flower (Peter and Johnson, 2008;Jersáková et al, 2016). In this scenario, resemblance between mimic and model should be close enough that pollinators are sometimes unable to reliably discriminate between them (Jersáková et al, 2016). Specifically, here we use published data from Peter and Johnson (2008) on petal color from the mimic Eulophia zeyheriana (Orchidaceae) and the rewarding flower Wahlenbergia cuspidata (Campanulaceae) (Figure 1) to test this hypothesis.…”